JPH04202644A - Silicon steel sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a silicon steel sheet having high magnetic permeability on an industrial scale by allowing a decarburization accelerator to exist on the surface of a cold rolled steel sheet with a specific composition, exerting heating and holding at low temp. rise rate to decarburize the surface layer, successively performing decarburizing annealing, and regulating C concentration. CONSTITUTION:A separation agent at annealing, containing decarburization accelerator, is allowed to exist on the surface of a cold rolled steel sheet having a composition consisting of, by weight, 0.02-1% C, <=6.5% (Si+Al), <=0.01% N, <=5.0% (Ni+Mn), one or more elements among Sb, P, and As so that (Sb+P +As) is regulated to 0.02-0.2%, and the balance Fe with inevitable impurities. Subsequently, this steel sheet is heated and held to and at a temp. in the region which is alpha+gamma two phase region or gamma-single phase region temp. and becomes (alpha-single phase region after decarburization at <=10 deg.C/min temp. rise rate, by which the depth range of 5-250mum from the surface is decarburized. After furnace cooling, decarburizing annealing is performed and C content in the whole cold rolled steel sheet is regulated to <=0.01%.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention can be used, for example, as an iron core material for motors, transformers, etc. This invention relates to a magnetic steel sheet and its manufacturing method. More specifically, the present invention relates to an electrical steel sheet in which <100> axes are highly concentrated in the direction perpendicular to the sheet surface and has extremely high magnetic permeability, and a method for manufacturing the same. [Prior Art] In recent years, in order to reduce power loss and downsize equipment in which tMi steel sheets are used, there has been a strong demand for improved magnetic properties of the electrical steel sheets, such as lower iron loss and higher magnetic flux density. It is being In particular, in the case of electromagnetic steel sheets used in equipment used in direct current, it is required to have high magnetic permeability. Specifically, the maximum magnetic permeability μIIax is 30,000
(Gaussloe) or higher is required. Techniques that can increase the magnetic permeability of steel plates include - For boat fishing, it is known to reduce the amount of impurities contained in the steel plate, or to increase the crystal grain size of the steel plate to a certain extent. However, in order to dramatically improve this magnetic permeability, it is most effective to align the <100> axis, which is the axis of easy magnetization, with the direction of magnetization. As described above, as a technology to dramatically increase the magnetic permeability of a steel plate by aligning the <100> axis in the direction perpendicular to the plate surface, the present applicant has previously developed a technology in which C and N are When a cold-rolled steel sheet containing carbon dioxide is annealed in a weakly decarburizing atmosphere at a high temperature of 800°C or higher, the surface layer transforms from the T phase or (α+γ) two phase to the α phase due to decarburization. Electrical steel sheets and their A manufacturing method was proposed.

[Problem to be solved by the invention]

With the technology proposed in JP-A-1-108345, the average crystal grain size of the obtained steel sheet is as small as 1 mm 1 m1 or less, so there is a limit to the effect of improving the magnetic permeability of the electrical steel sheet that can be obtained by this proposal, and the upper limit is , the maximum magnetic permeability is approximately 25,000 (Gaussloe). However, as mentioned above, there is a strong demand for improved magnetic permeability of electrical steel sheets in recent years, and the maximum magnetic permeability is 30,000 (G
aussloe), therefore, the above-mentioned Japanese Patent Application Laid-Open No. 1-1
The electromagnetic steel sheet obtained by the technique proposed in Publication No. 08345 is currently insufficient in terms of the requirement for improved magnetic permeability. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrical steel sheet having high magnetic permeability, which is currently required, and a method for manufacturing the same.

[Means to solve the problem]

The present inventors have conducted various studies to achieve the above object. As a result, the present inventors lowered the temperature increase rate during decarburization to be approximately the same as the temperature increase rate during box annealing, and annealed a cold rolled steel sheet containing C and N. As a result, it was found that the crystal grain size of the final product becomes larger and the <100> axis is strongly oriented in the direction perpendicular to the plate surface, compared to the conventional case where the heating rate is high. However, as a result of further studies, the present inventors found that simply lowering the temperature increase rate during decarburization would result in the cementite in the steel sheet turning into graphite during annealing and causing significant grain growth, resulting in surface energy acting on the steel sheet. In the temperature range (1mm1)
This results in coarse grains that are also oriented in planes, etc., and it is extremely effective to dramatically improve orientation in the (100) plane due to surface energy, that is, magnetic permeability, and high-density orientation in the 100> axis is difficult to occur. I found out that it would happen. In other words, the graphitization of cementite results in <100>
This means that high-density orientation toward the axis has been prevented. As a result of further investigation into means that can prevent graphitization during decarburization due to a low temperature increase rate, the present inventors found that adding an appropriate amount of elements that tend to segregate in steel, such as 5b-P and As, , these elements act as so-called graphitization inhibiting elements, and the
It has been found that it is possible to obtain an electromagnetic steel sheet that has high magnetic permeability, in which the axes are highly integrated, and the average crystal grain size in the direction parallel to the sheet surface exceeds T1. Furthermore, industrially, the annealing must be performed in a tight coil state to prevent buckling, but as previously proposed by the present inventors in Japanese Patent Application Laid-Open No. 2-156024, In order to decarburize uniformly in the width direction of the coil, decarburization occurs in the center of the coil width direction (
A so-called decarburization accelerator, which promotes decarburization, may be mixed with the annealing separator, such as alumina and/or magnesia, which is used to prevent decarburization. The present inventors have completed the present invention as a result of further extensive studies based on the above-mentioned knowledge and known facts. Here, the gist of the present invention is, in weight%, c: o, oi% or less, Si + Al: 6.5
% or less, N: 0.01% or less, Ni + Mn:
5.0% or less, Sb+P+As: 0.02~
An electrical steel sheet having a steel composition consisting of at least one of the three elements Sb, P, and ^S that satisfies the relationship of 0.2%, the balance being Fe and unavoidable impurities, (i) vertical to the sheet surface; (ii) the average diameter of the columnar grains in the direction parallel to the plate surface is greater than [I; and (ij) in the direction perpendicular to the plate surface. This is a high magnetic permeability electrical steel sheet characterized by a high density of 400> axes. Moreover, in order to manufacture the above-mentioned electromagnetic steel sheet according to the present invention, -
For boat fishing, the weight percentages are as follows: C: 0.02-1%, Si+^]: 6.5% or less, N: 0.01% or less, Ni: 5.0%
Hereinafter, a cold-rolled steel sheet having a steel composition consisting of at least one of the three elements Sb, P, and As satisfying the relationship of Sb + P + As: 0.02 to 0.2%, the balance being Fe and inevitable impurities. A decarburization accelerator contained in an annealing separator was present on the surface of the 10° (:
/win at a temperature increase rate of less than or equal to 250μ
m range, and then decarburization annealing is performed until the C content of the cold rolled steel sheet becomes 0.01% or less. In addition, when the plate thickness of the cold-rolled steel plate is 0.5-■ or less, in weight%, C: 0.02-1%, Si+^I: 6.5% or less, N: 0.01%. Below, Ni + Mn: 5
．． 0% or less, Sb+P+As: 0102-0.
It has a steel composition consisting of at least one of the three elements Sb, P and ^S that satisfies the relationship of 2%, the balance being Fe and unavoidable impurities, and the plate thickness is 0.5 m or less. A decarburization accelerator contained in an annealing separator is present on the surface of a cold rolled steel sheet, and the temperature is in the α + γ two phase region or the γ single phase region at a temperature increase rate of 10 ° C / min or less. The C content of the entire cold rolled steel sheet may be reduced to 0.01% or less by heating and maintaining the temperature in the α single phase region after decarburization.

[Function] Hereinafter, the present invention will be explained in detail together with the function and effect. In this specification, "%" means "% by weight" unless otherwise specified. First, the reason for limiting the composition of the electrical steel sheet according to the present invention will be explained. C: 0.01% or less In order to expand the T phase region and control the texture by (α+γ)→α transformation or T→α transformation, the C content should be reduced to 0 at the stage before the final annealing described below. It is effective to set the content to .02% or more, while it is effective to set the upper limit to 1% or less, preferably 0.3% or less in order to suppress a significant increase in decarburization time. The C content after final annealing is set to 0.01% or less, preferably 0.003% or less, in order not to deteriorate the magnetic properties. Therefore, the C content of the electric Mi steel sheet is limited to 0.01% or less. Si+Al: 6.5% or less Both Si and Al are preferably added to increase mechanical strength, but if added in excess of 6.5%, the product becomes brittle. Therefore,! The total content of each of Si and AI in the magnetic steel sheet is limited to 6.5% or less. The lower limit is desirably set to 0.01% or more from the viewpoint of deoxidation. N: 0.01% or less When N exists in steel, it tends to generate precipitates that are harmful to magnetic properties. Therefore, it is preferable that the content be small, but a significant reduction incurs a corresponding increase in cost, and there is no particular problem if the content is about 0.01%. Therefore, the N content is limited to 0.01% or less. Ni + Mn: 5.0% or less Both Ni and Mn are added to increase mechanical strength, but when added in excess of 5.0%, the decarburized grains in the surface layer of the cold rolled steel sheet become α single phase at the annealing temperature. Otherwise, it becomes impossible to control the texture. Therefore, Ni
, The total content of Mn is limited to 5°0% or less. Sb, P, As: 0.02% or more and 0.2% or less in total These elements suppress graphitization of cementite during annealing by effectively segregating into pores generated during cold rolling etc. It has the effect of This effect of suppressing graphitization is not effective when the total content of these elements is less than 0.02%;
If the content is larger, the rollability of the cold rolled steel sheet will decrease. Therefore, the total amount of these elements is limited to 0.02% or more and 0.2% or less. In addition, the elements and their amounts that do not destroy the effects of the present invention even if added as desired are as follows. 0051%, Mo51%, Cr51%, Cu51%, 5
505%, Se≦0.05%, B≦0.01%, Te≦
0.1%, 750.05%, TiS2.05%. The composition of the tm steel plate other than the above is Fe and inevitable impurities. The t-magnetic steel sheet according to the present invention has the composition as described above,
and (1) in the direction perpendicular to the plate surface, that is, in the direction intersecting the plate surface,
It has columnar crystal grains that grow from the surface toward the inside, and (1 mm) the average diameter of the columnar crystal grains in the direction parallel to the plate surface is greater than Is-, and (iii) <100 mm in the direction perpendicular to the plate surface. > It is characterized by a high density of axes. That is, in the 1t steel sheet according to the present invention, columnar crystal grains basically grow from the surface to the inside in the direction perpendicular to the sheet surface, and the axis of easy magnetization is <100> in the direction perpendicular to the sheet surface.
Because the shaft has a densely packed structure, it has high magnetic permeability. Furthermore, in the electrical steel sheet according to the present invention, since the average diameter of the columnar crystal grains is more than 1 mm1II+, the magnetic permeability is extremely high compared to conventional electrical steel sheets, and the desired magnetic properties are achieved. Therefore, it is possible to provide an electromagnetic steel sheet having the following characteristics. Next, a method for manufacturing an electrical steel sheet according to the present invention will be explained. First, as mentioned above, by containing 0.02% or more of C, the γ phase region is expanded and grain boundary segregation of Sb,
A cold-rolled steel sheet containing at least one of the three elements p and As in an amount specified by the present invention, for example, in weight%: C: 0.02-1%, Si + Al: 6.5 % or less, N: 0.01% or less, Ni+Mn: 5.
0% or less, Sb+P+As: 0.02-0.2
% relationship, at least one of the three elements consisting of Sb, P and As, the balance being Fe and unavoidable impurities. There is also a decarburization promoting side. This cold-rolled steel plate is not particularly limited as long as it is obtained by cold rolling. Here, cold rolling refers to rolling at a temperature of 500° C. or lower without recrystallization. In cold rolling, it is desirable to perform rolling at a rolling reduction ratio of preferably 20% or more, more preferably 50% or more. Further, rolling may be performed multiple times with intermediate annealing interposed therebetween. There is essentially no limit to the plate thickness, but from a practical standpoint, it is desirable that it be 2Ils or less since decarburization takes a long time. Decarburization accelerators include, for example, Fe, Ti, ■, Nb, Ta.
, Zr, Cr, , W, Mo, Mn, Cu, N
Examples include powders of alloys, compounds, or oxides containing one or more elements selected from the group consisting of i, Sl, and pb; It is not limited only to charcoal promoters. Furthermore, the particle size of the powder of the decarburization accelerator is not particularly limited. In normal cases, it is desirable to have a particle size in the range of about 1 to 150 μm from the viewpoint of effectively promoting the decarburization reaction. The means for causing a decarburization accelerator to be present on the surface of the cold rolled steel sheet also includes:
There are no particular limitations, and the annealing component may be first separated during autopsy, and then applied or dispersed using an appropriate device, for example. After the decarburization accelerator is made to exist on the surface of the cold-rolled steel sheet having the above composition in this manner, the cold-rolled steel sheet is wound into a tight coil. In the present invention, the tight coil has 10
Annealing is carried out by heating and holding at a low temperature increase rate of less than °C/1 Iln to a temperature range of the (α+γ) two-phase region or the T single-phase region, which becomes the α single-phase region after decarburization. The temperature range of this α+T2 phase region or T single phase region, which becomes the α single phase region after decarburization, is, for example, Fe-3%5t-
This corresponds to the shaded area shown in FIG. 1, which is a phase diagram showing the 3% Mn--C system. In addition, in this Figure 1, 1mm 00℃
The reason why the shaded area is separated by is that even if decarburization is carried out at 1 mm or higher and the α single phase occurs, the texture changes as it passes through the α+12 phase region during cooling. This annealing is performed for the purpose of preventing significant oxidation and decarburization on the surface of the cold rolled steel sheet.
In a vacuum in the temperature range of 00 to 1200℃ or with a dew point of -2
CO gas, CO based on inert gas below 0°C
□ Bright annealing is performed in a weakly decarburizing atmosphere containing a mixture of gas, hydrogen gas, etc. The soaking time is determined by the composition, temperature, and atmosphere. By subjecting the cold-rolled steel sheet to such annealing, the range from 50 μm to 250 pm from the surface of the cold-rolled steel sheet is decarburized to become a decarburized layer, which becomes an α single phase. The interior of the cold-rolled steel sheet outside the above range remains the (α+γ) two-phase or T single-phase as before. Note that the thickness of this decarburized layer increases as the amount of C in the cold rolled steel sheet decreases, as the annealing temperature increases, or as the annealing time increases. As mentioned above, bright annealing can decarburize a maximum of 500 μm on both sides of a steel sheet. By simply performing annealing, the entire steel plate is completely decarburized without the need for any other decarburization treatment. When decarburizing in a weakly decarburizing atmosphere such as bright annealing, which is suitable for use in the present invention, the surface portion of a cold rolled steel sheet is easily decarburized, but even the inside beyond 250 μm from the surface is decarburized. It takes a very long time to decarburize. Therefore, the α grains on the surface grow only slowly inward, and grow two-dimensionally in the in-plane direction of the cold rolled steel sheet. At this time, crystal grains having a <100> axis perpendicular to the plate surface grow preferentially, and the α single phase region on the surface becomes a structure in which the <100> axis is strongly oriented in the direction perpendicular to the plate surface. The average diameter of the α grains on this surface is usually 100 to 1000μ.
m, and when the plate thickness is thinner and the decarburized layer penetrates to the inside, it exceeds l+ms. Subsequently, the cold-rolled steel sheet that has been annealed in a weakly decarburizing atmosphere is then annealed at 600°C or higher in a strongly decarburizing atmosphere where strong decarburization occurs, for example, in hydrogen with a dew point of +30°C. At the temperature at which α becomes a single phase after decarburization, the C content is 0.01
% or less. By performing annealing in such a strongly decarburizing atmosphere, the α grains on the surface of the cold rolled steel sheet grow in the direction of the sheet surface and are present inside the cold rolled steel sheet (α + cementite). ) two-phase region, (α + γ) two-phase M region or γ single-phase region, forming an α-phase columnar grain structure, and the crystal grains in the direction parallel to the plate surface are coarse and exceed 1 mm. become At this time, the +100) set &lIm generated on the surface of the cold-rolled steel sheet grew into the interior along with the growth of the α crystal grains, and the <100> axis was strongly oriented in the direction perpendicular to the sheet surface.
The electrical steel sheet according to the present invention can be manufactured. In this way, according to the present invention, 400
>It becomes possible to manufacture an electric msi plate with highly integrated shafts and high magnetic permeability. Further, the present invention will be explained in detail using examples, but these are illustrative of the present invention and the present invention is not limited thereby. [Example 1] Steel types A to J having the compositions shown in Table 1 were vacuum melted to create ingots, then hot rolled to a thickness of 3 mm, and then 0.8 mm thick. Cold rolling was performed until the thickness was reached, and a cold rolled steel plate was obtained. The surface of the obtained cold-rolled jllFi was coated with a mixed powder of alumina and iron oxide, and wound into a tight coil at a heating rate of 0°5° (/+w), which corresponds to the temperature increase rate in normal box annealing.
The material was heated at a temperature increase rate of in and kept at 920°C for 5 hours, which is the temperature in the α+T2 phase region or the T single phase region and becomes the α single phase region after decarburization, and then cooled in the furnace. The atmosphere was a vacuum of 10-'' Torr. Then, after the furnace was cooled, decarburization annealing was performed at 800°C for 1 hour in a Hz/Nz mixed gas with a dew point of +30°C. After charcoal annealing, the grain size, <100> fine density, and maximum magnetic permeability of the surface of the cold rolled steel sheet were measured. The <100> axial density and maximum magnetic permeability were measured as follows. (al < 100 > Axial density ECP (Electron channel Pat
ern) method, 200 crystal grains were measured, and the ratio of the number of crystal grains having <100> axes at ±5°5° from the perpendicular direction to the plate surface to the total was calculated as the ratio of the number of grains with no orientation. It was calculated as the divided value. (b) Maximum permeability JIS standard ring test piece (outer diameter 45vw, inner diameter 33m
1 mm) were taken, and this test piece was heated at 750°C for 2 hours.
After being subjected to strain relief annealing for several hours, six sheets were stacked one on top of the other and measured. The results are summarized in Table 2. By the method according to the present invention, the in-plane average grain size on the surface of the steel sheet becomes larger than Ll, and the degree of integration is high (10
It is clear that a 01-plane texture is formed. Therefore, it can be seen that the maximum magnetic permeability of the cold-rolled steel sheet of the example of the present invention is significantly improved compared to the cold-rolled steel sheet of the comparative example. On the other hand, in Table 2, steel types G include P, Sb,
Because the total amount of As was less than 0.02%, graphitization occurred during annealing, and although the crystal grains became coarse, the maximum magnetic permeability was low because the <100> axis did not develop. . In steel type H, the total amount of Si and AI exceeded 6.5%, while in steel type J, the total amount of P, Sb, and As exceeded 0°2.
%, all of them broke during cold rolling. Furthermore, in steel type (III), since the decarburized grains in the surface layer did not become α single phase at the annealing temperature (920°C), it was not possible to control the aggregated Mi weave, which is the objective of the present invention, and the maximum magnetic permeability has also become a low value. Thus, the effects of the present invention are clear from Example 1 as well.

[Example 2] Steel type A having the composition shown in Table 1 was vacuum melted to create an ingot, then hot rolled to a thickness of 2.5-1, and then ingot with a thickness of 0.5-1. Cold rolling was performed until the steel sheet became thick, and a cold-rolled steel sheet was obtained. The surface of this cold-rolled sheet was coated with various annealing separators shown in Table 3, and wound into a tight coil at a heating rate of 0.5°C/min, which corresponds to the heating rate of normal box annealing. 7 at 950°C, which is the temperature range of α + T2 phase region or T single phase region and becomes α single phase region after decarburization.
After holding for a period of time, the mixture was cooled in the furnace. The atmosphere was Ar gas with a dew point of -45°C - 3% by volume.
It is H2 gas. After cooling the cold rolled steel sheet in the furnace, continue to apply H2N with a dew point of +30°C.
Decarburization annealing was performed in a Z mixed gas at 800'C for 1 mm time. Annealing After annealing, the grain size, <100> fineness, and maximum magnetic permeability of the surface of the obtained electrical steel sheet were measured. Note that <100> axis density is ECP (Electron
200 crystal grains were measured using the channel pattern method, and <1
The ratio of the number of crystal grains having a 00> axis to the total was divided by the ratio of the number of crystal grains having no orientation. In addition, the maximum magnetic permeability is determined by taking 10 JIS standard ring test pieces (outer diameter 45I, inner diameter 33 mm), and subjecting the test pieces to strain relief annealing at 750°C for 2 hours. It was determined by overlapping and measuring. The results are also shown in Table 3. As is clear from Table 3, by using the annealing separator within the range of the present invention, the average grain size on the surface of the electrical steel sheet after final annealing becomes larger than 1 slI, and the degree of agglomeration is reduced. It can be seen that the maximum magnetic permeability is significantly improved because a high +1001 plane integrated structure is formed.

[Example 3] After creating an ingot by vacuum melting steel type B having the composition shown in Table 1, it was hot rolled to a thickness of 2.31 mm, then intermediate annealed, and finally 0.35mm
A cold-rolled steel plate was obtained by cold rolling until the thickness of the steel sheet was reached. The surface of the obtained cold-rolled steel sheet is coated with Cr1es powder and wound into a tight coil, and after heating at various heating rates, it is found to be in the α + γ two-phase region or the T single-phase region, and after decarburization, it becomes α single-phase. The sample was maintained at a temperature of 1000°C for 24 hours, and then cooled in a furnace. Note that the atmosphere is a vacuum of 10-2 Torr. Also,
In the case of this example, since the plate thickness was as thin as 0.35 mm, the annealing temperature was relatively high, and the annealing time was also long, the entire steel plate was decarburized only by bright annealing. After bright annealing, the crystal grain size on the surface of the cold rolled steel sheet, do
o> Axial density and maximum permeability were measured. In addition, <100> lllke degree is ECP (Elec
By the tron channel pattern) method,
200 crystal grains were measured, and the ratio of the number of crystal grains having a <100> axis within ±5° from the direction perpendicular to the plate surface to the total was divided by the ratio of the case without orientation. In addition, the maximum magnetic permeability was determined by taking 14 JIS standard ring test pieces (outer diameter 45 Nll-1 inner diameter 33 Nll), and subjecting the test pieces to strain relief annealing at 750°C for 2 hours. were measured by overlapping them. The results are shown in Table 4. From Table 4, it can be seen that the maximum magnetic permeability of the samples annealed at a temperature increase rate that satisfies the range of the present invention is significantly superior to that of the comparative sample.

【Effect of the invention】

As detailed above, the present invention has made it possible to produce electric M1 steel sheets with excellent magnetic properties on an industrial scale. The significance of the present invention having such effects is extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a phase diagram showing the Fe-3%5i-3%Mn-C system.

Claims (3)

[Claims] (1) In weight%, C: 0.01% or less, Si+Al: 6.5% or less, N:
0.01% or less, Ni+Mn: 5.0% or less, Sb+P
+As: Sb, P satisfying the relationship of 0.02 to 0.2%
An electrical steel sheet having a steel composition consisting of at least one member selected from the group consisting of and As, the balance being Fe and unavoidable impurities, comprising: (i) columnar crystals grown from the surface to the inside in a direction perpendicular to the sheet surface; (ii) the average diameter of the columnar crystal grains in the direction parallel to the plate surface is more than 1 mm, and (iii) <100> axes are densely accumulated in the direction perpendicular to the plate surface. Electrical steel sheet with high magnetic permeability. (2) In weight%, C: 0.02 to 1%, Si+Al: 6.5% or less, N:
0.01% or less, Ni+Mn: 5.0% or less, Sb+P
+As: Sb, P satisfying the relationship of 0.02 to 0.2%
A decarburization promoter contained in an annealing separator is present on the surface of a cold-rolled steel sheet having a steel composition consisting of at least one member selected from the group consisting of /m
At a temperature increase rate of less than in
holding the cold rolled steel sheet, decarburizing a range of 5 to 250 μm from the surface toward the inside, and then decarburizing and annealing the cold rolled steel sheet until the C content of the entire cold rolled steel sheet becomes 0.01% or less. Method of manufacturing steel plates. (3) In weight%, C: 0.02 to 1%, Si+Al: 6.5% or less, N:
0.01% or less, Ni+Mn: 5.0% or less, Sb+P
+As: Sb, P satisfying the relationship of 0.02 to 0.2%
and As, contained in an annealing separator on the surface of a cold-rolled steel sheet having a steel composition consisting of the balance Fe and unavoidable impurities and having a thickness of 0.5 mm or less. In the presence of a decarburization promoter, α
+γ2-phase region or γ single-phase region temperature range, after decarburization α
A method for manufacturing an electrical steel sheet, characterized in that the C content of the entire cold-rolled steel sheet is reduced to 0.01% or less by heating and maintaining the temperature in a single-phase temperature range.