JPH09125145A - Production of nonoriented silicon steel sheet high in magnetic flux density and low in iron loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a nonoriented silicon steel sheet high in magnetic flux density, low in iron loss and used as the material for the iron core of electric apparatus. SOLUTION: In the method for producing a nonoriented silicon steel sheet in which a slab having components contg., by weight, 0.10 to 2.50% Si, at least one kind of 0.10 to 1.00% Al and 0.10 to 2.00% Mn so as to satisfy Si+2Al<=2.50% as well, furthermore satisfying <=0.0025% C, <=0.0020% N, <=0.0020% S, <=0.0030% Ti, <=0.0030% Nb, <=0.0050% V and <=0.0030% As, and the balance Fe with inevitable impurities and having αγ transformation is used and is subjected to hot rolling to form into a hot rolled sheet, which is subjected to hot rolled sheet annealing and a cold rolling step for one time and is next subjected to finish annealing, the hot rolled sheet annealing is executed in the temp. range of the Ac3 point or above for 10sec to 5min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties with high magnetic flux density and low iron loss, which is used as an iron core material of electric equipment.

[0002]

2. Description of the Related Art In recent years, in the field of electric machines, especially rotating machines and non-oriented electrical steel sheets used as iron core materials thereof, and small and medium-sized transformers, world-wide power and energy saving, and CFC regulation. In the movement of global environment conservation such as the above, the movement for higher efficiency is spreading rapidly. Therefore, there is an increasing demand for non-oriented electrical steel sheets to improve their properties, that is, to have high magnetic flux density and low iron loss.

By the way, in the non-oriented electrical steel sheet,
Conventionally, a method of increasing the content of Si, Al, or the like has been generally used as a means for reducing iron loss from the viewpoint of reducing eddy current loss due to increase in electrical resistance. However, this method, on the other hand, has a problem that the decrease in magnetic flux density cannot be avoided. In order to overcome such problems, a method of improving both the magnetic flux density and the iron loss by increasing the crystal grain size of the hot-rolled sheet has been performed.

Conventionally, in the production of a non-oriented electrical steel sheet having a transformation, the grain size before cold rolling is secured by ending hot rolling in the vicinity of the upper limit of the α range, resulting in the magnetic flux density and iron loss of the product. Improvements have been made. From this point of view, JP-A-56-38420 discloses that the hot rolling end temperature is set to 6% or less of the intermediate temperature between Ar ₃ point and Ar ₁ point.
A method for coarsening a hot rolled crystal structure by winding at a temperature of 80 ° C. or higher is disclosed.

However, in an actual finishing hot rolling machine, since the rolling speed at the time of biting and the rolling speed in the steady rolling state are necessarily different, it is difficult to eliminate the temperature distribution in the coil longitudinal direction, and the α range In order to carry out hot rolling at the upper limit of 1, there was the disadvantage that the rolling set temperature had to be lowered.

Further, since the A ₁ transformation point of general low-grade non-oriented electrical steel sheets is around 900 ° C., it is limited to increase the hot rolling end temperature to grow the hot rolled crystal structure. However, there is a limit to the improvement of the magnetic properties by increasing the crystal structure before cold rolling. Furthermore, it is considered that the hot rolling end temperature rises to the γ range because the hot rolling structure becomes finer due to the progress of the transformation to the α phase after the hot rolling and the magnetic properties deteriorate as a result. Came.

As a technique for overcoming the limit of coarsening of the crystal structure before cold rolling by such controlled hot rolling, Japanese Patent Application Laid-Open No. 57-35 is known.
In Japanese Patent No. 628, after the hot rolling end temperature is set to Ar ₃ point or more to make the hot rolled crystal structure finer, the hot rolled sheet is annealed at a temperature of Ac ₃ point or lower to obtain a coarse crystal structure before cold rolling. A method for achieving this is disclosed. However, performing hot-rolled sheet annealing in the γ region has an upper limit in the operating temperature because the crystal structure becomes finer with the transformation from the γ phase to the α phase during cooling, and the hot rolling of the above-described controlled hot rolling ends. As with temperature control, there was a natural limit.

Similarly, as a method for suppressing the increase in cost due to the addition of the hot-rolled sheet annealing step and for coarsening the crystal structure before cold rolling, the hot-rolled sheet is wound at a high temperature and annealed by the heat possessed by the coil. The self-annealing method is disclosed in JP-A-54-76422 and JP-A-58-136718. However, in the examples of these prior inventions, self-annealing was all performed in the α phase region for the same reason, and there was a limit to the coarsening of the crystal structure before cold rolling.

As a method of overcoming the limitation of improving the magnetic properties of the non-oriented electrical steel sheet by the conventional hot-rolled sheet annealing and self-annealing, Japanese Unexamined Patent Publication No. 3-204420 discloses a coiling temperature for finish hot rolling. Ar from Ar ₃ point as _three or more Ar
A technique for controlling the average cooling rate up to _one point to 50 ° C./second or less is disclosed. However, there is a problem in that the magnetism in the longitudinal direction of the coil becomes non-uniform due to the non-uniform temperature distribution in the coil due to the winding at a high temperature of Ar ₃ points or higher.

Further, Japanese Patent Laid-Open No. 6-57332 discloses that
Hot-rolled sheet annealing is performed in the γ region, and then Ar ₃ points to Ar ₁
A method of controlling the cooling rate up to the point to 5 ° C./second or less, and JP-A-6-240360 discloses that hot-rolled sheet annealing is A
c After performing the test in a temperature range of ₁ point or more, from Ar ₃ point to Ar ₁ point
A technique for controlling the cooling rate up to the point to 50 ° C./second or less is disclosed. However, in this technique, since it is necessary to reduce the cooling rate, there is a problem that the annealing time is inevitably lengthened and the productivity is lowered. Further, in these prior arts, the variation of the magnetic properties due to the change of the cooling rate from the Ar ₃ point to the Ar ₁ point is large, and it is extremely difficult to manufacture a non-oriented electrical steel sheet with stable magnetic properties in the longitudinal direction of the strip. Met.

On the other hand, from the viewpoint of improving the magnetic characteristics by controlling the components, not only is the content of Si or Al increased in order to reduce iron loss, but it is described in Japanese Patent Publication No. 6-80169. As described above, a method of making the precipitate harmless by making high-purity steel by reducing Mn and S is disclosed. However, improvement of magnetic flux density is not enough only by purifying steel, and there is a limit to the development of a non-oriented electrical steel sheet excellent in both iron loss and magnetic flux density.

Further, as a method for improving the magnetic properties of the non-oriented electrical steel sheet by improving the primary recrystallization texture, Sn addition as disclosed in JP-A-55-158252 and JP-A-62-180014 is disclosed. Sn, C as in the publication
A method for producing a non-oriented electrical steel sheet having excellent magnetic properties by improving the texture by adding U or adding Sb as disclosed in JP-A-59-100217 is disclosed. However, the addition of Sn, Cu, Sb, or the like, which is a texture control element, causes an increase in cost, and there has been a limit in providing a low-cost method for producing a non-oriented electrical steel sheet.

In addition, although measures in the manufacturing process such as devising a finish annealing cycle as described in JP-A-57-35626 have been taken, the iron loss reduction is achieved in all cases. However, there was not much effect on the magnetic flux density. As described above, the conventional technology has not been able to manufacture a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss, and has not been able to meet the above-mentioned demand for a non-oriented electrical steel sheet.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems in the prior art and to provide a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss.

[0015]

The gist of the present invention is as follows. That is, (1) wt% in steel
0.10% ≦ Si ≦ 2.50%, C ≦ 0.0025%, N ≦ 0.0020%, S ≦ 0.0020%, Ti ≦ 0.0030%, Nb ≦ 0.0030%, V ≦ 0.0050%, As ≦ 0.0030%, and the balance α consisting of Fe and inevitable impurities
Using a slab of a component having a γ transformation, hot rolling into a hot rolled sheet, hot rolled sheet annealing and one cold rolling step, followed by finish annealing Annealing of rolled sheet in the temperature range of Ac ₃ points or more for 10 seconds to 5
(2) 0.10% ≤ Si ≤ 2.50%, at least Mn and Al are included in the steel. One kind, 0.10% ≦ Al
≦ 1.00%, 0.10% ≦ Mn ≦ 2.00%, and the total amount of Si and Al is Si + 2Al ≦ 2.50%, C ≦ 0.0025%, N ≦ 0.0020% , S ≦ 0.0020%, Ti ≦ 0.0030%, Nb ≦ 0.0030%, V ≦ 0.0050%, As ≦ 0.0030%, and the balance α consisting of Fe and unavoidable impurities
Using a slab of a component having a γ transformation, hot rolling into a hot rolled sheet, hot rolled sheet annealing and a method of producing a non-oriented electrical steel sheet subjected to one cold rolling step and then finish annealing, Annealing of hot rolled sheet in the temperature range of Ac ₃ points or more for 10 seconds ~
A method for manufacturing a non-oriented electrical steel sheet, which is carried out for 5 minutes.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. As a result of intensive studies of the problems in the prior art in order to achieve low iron loss and high magnetic flux density at the same time, the inventors have found that in a non-oriented electrical steel sheet having a transformation, Si is 0.10%.
% To 2.5%, 0.10% to 1.0% Al, 0.10% to 2.0% Mn, and a αγ transformation steel, the C, S and N contents are reduced. In addition, Ti,
By reducing the V, Nb, and As contents at the same time, it becomes a high-purity steel, and the annealing temperature of the hot-rolled sheet is set to a temperature range of Ac ₃ point or higher, so that the hot-rolled sheet is annealed in a short time and hot rolled more than before. It has been found that it is possible to manufacture a non-oriented electrical steel sheet with a coarse crystal structure and a high magnetic flux density and a low iron loss.

The magnetic properties of the non-oriented electrical steel sheet can be improved by coarsening the crystal structure before cold rolling. Therefore, conventionally, it is possible to increase the hot rolling end temperature in finish hot rolling, or to roughen the crystal structure by hot rolling sheet annealing as a more effective method to increase the magnetic flux density of the product and reduce iron loss. Has been done. However, when the annealing temperature of the hot-rolled sheet is increased to reach the α + γ2 phase region or the γ region, the transformation from the γ phase to the α phase progresses after the annealing is completed, and the hot rolled structure becomes fine-grained, resulting in deterioration of magnetic properties. Therefore, it has been said that it should be avoided.

In addition, since the A ₁ transformation point of a low grade non-oriented electrical steel sheet having a low Si content is around 900 ° C., there is a limit to the rise of the hot rolled sheet annealing temperature, and the crystal structure before cold rolling is limited. There was a limit to the improvement of magnetic characteristics by increasing the magnetic field.

As a method for overcoming such a limitation of improving the magnetic properties of the non-oriented electrical steel sheet in the conventional hot-rolled sheet annealing, JP-A-6-57332 and JP-A-6-24 are cited.
Japanese Patent No. 0360 discloses a method of controlling the cooling rate from the Ar ₃ point to the Ar ₁ point to a certain value or less after performing hot-rolled sheet annealing in the temperature range of the Ac ₁ point or higher. However, in this technique, the cooling rate is lowered, so that not only the productivity is lowered, but also when the cooling rate from the Ar ₃ point to the Ar ₁ point is changed, the magnetic properties of the product are largely changed, and It was extremely difficult to manufacture a non-oriented electrical steel sheet with stable magnetic properties.

The inventors of the present invention have conducted extensive studies in order to overcome the limitations of the conventional technique for improving the magnetic properties of conventional non-oriented electrical steel sheets having such transformation, and as a result, the non-oriented electrical steel sheet having transformations has been found. , Si 0.10% to 2.5
%, Al 0.10% to 1.0%, Mn 0.10% to
In a steel containing 2.0% and having αγ transformation, the contents of C, S and N are reduced, and further, Ti, V, Nb, As
If a high-purity steel is obtained by simultaneously reducing the content, even if the hot-rolled sheet annealing temperature is increased to the γ range, the crystal structure of the α phase after transformation does not become fine, and the magnetic flux in the product after finish annealing is reduced. Not only the density is extremely high and the iron loss is good (the iron loss value is low), but further, the magnetic properties are less dependent on the cooling rate after hot-rolled sheet annealing, and the magnetic flux density is stable and the iron loss is low. It was found that the non-oriented electrical steel sheet of can be manufactured.

First, the components will be described. Si is added to increase the specific resistance of the steel sheet, reduce eddy current loss, and improve the iron loss value. If the Si content is less than 0.10%, a sufficient specific resistance cannot be obtained, so it is necessary to add 0.10% or more. On the other hand, if the Si content exceeds 2.50%, αγ transformation does not occur, so it is necessary to set it to 2.50% or less.

Al, like Si, has the effect of increasing the specific resistance of the steel sheet and reducing the eddy current loss. For this purpose, it is necessary to add 0.10% or more. On the other hand, Al
If the content exceeds 1.00%, the magnetic flux density decreases and the cost increases, so the content is set to 1.00% or less. further,
If (Si + 2Al) exceeds 2.50%, αγ transformation does not occur, so (Si + 2Al) ≦ 2.50% must be satisfied. Also, the Al content in the steel is 0.10%
Even if it is less than the above, the effect of the present invention is not impaired at all.

Similar to Al and Si, Mn has the effect of increasing the specific resistance of the steel sheet and reducing the eddy current loss. Therefore, the Mn content needs to be 0.10% or more.
On the other hand, if the Mn content exceeds 2.0%, the deformation resistance during hot rolling increases and hot rolling becomes difficult, and the crystal structure after hot rolling tends to become finer, which deteriorates the magnetic properties of the product. The Mn content needs to be 2.0% or less. Further, since the αγ transformation point is lowered by the addition of Mn, it is possible to lower the lower limit Ac ₃ point of the hot-rolled sheet annealing temperature in the present invention, which saves energy required for heating during annealing and reduces cost. The addition of Mn is effective in that the oxide formation on the surface of the steel sheet can be suppressed and the pickling yield is improved. From the viewpoint of such transformation point control, the Mn content is 0.30% to 1.50%.
It is preferred that

The control of the C content is an essential point of the component definition of the present invention, and it is necessary to control the content to 0.0025% or less. If the C content exceeds 0.0025%, the crystal structure becomes finer due to the α + γ region after the hot-rolled sheet annealing or the transformation from the γ phase to the α phase, so the content must be 0.0025% or less.

S and N are partially re-dissolved during heating of the slab in the hot rolling process, and sulfides such as MnS and A during hot rolling.
Form a nitride such as 1N. The presence of these elements provides nuclei of the α phase at the time of transformation from the γ phase to the α phase after hot-rolled sheet annealing, and hinders the grain growth of the α phase crystal structure after transformation. It must be less than or equal to%.

The Ti content, V content, and Nb content are 0.0030%, 0.0030%, and 0.00, respectively.
If it exceeds 50%, precipitation of nitrides such as TiN, VN, NbN becomes remarkable, coarsening of the hot rolled crystal structure is hindered, and crystal grain growth in the finish annealing step is hindered to deteriorate magnetic properties.

Further, it is necessary to suppress the As content as a factor that influences the formation of precipitates that inhibit the growth of crystal grains. As, by itself, does not form precipitates such as the above-mentioned sulfides and nitrides in the steel within the composition range of the present invention. However, when a certain amount of As or more is contained in the steel, the sulfide size becomes fine, so that the coarsening of the hot rolled crystal structure is significantly hindered. From this perspective, A
The s content must be 0.0030% or less.

In order to improve the mechanical properties of the product, the magnetic properties, the rust resistance, or other purposes, P,
Even if one or more of B, Ni, Cr, Sb, Sn, and Cu are contained in the steel, the effect of the present invention is not impaired.
For example, P is added within the range of up to 0.1% in order to improve the punchability of the product. P ≦ 0.2
%, There is no problem from the viewpoint of magnetic properties of the product. B
Is added in order to form BN during hot rolling to prevent fine precipitation of AlN and render N harmless. B content is N
It is necessary to balance the amount of B and N, and the content thereof preferably satisfies the ratio of both B% / N% of 0.5 to 1.5.

Next, the process conditions of the present invention will be described. As a result of intensive studies, the inventors have controlled the content of impurities such as C, N, and S, Ti, V, Nb, As, and the like, and controlled the impurity components of the steel so that the hot-rolled sheet annealing can be performed by γ. When performed in the phase, the hot-rolled crystal structure is coarsened more than the conventional hot-rolled sheet annealing in the α phase region, and the influence of the change in the cooling rate after annealing on the magnetic properties of the product is small and stable. The present inventors have completed the present invention by discovering that excellent magnetic properties can be achieved.

The following experiments were conducted to examine the difference in the hot rolled crystal structure formation with respect to the annealing conditions and the cooling rate of the hot rolled sheet having such a steel purity. Steel having the components shown in Table 1 was melted and hot-rolled by finishing to finish it to a thickness of 2.5 mm. The hot rolled sheet annealing temperature was in the range of 800 ° C to 1050 ° C.
This was pickled and cold rolled to a thickness of 0.5 mm. Further, it was degreased, annealed at 720 ° C. for 30 seconds, and an Epstein sample was cut out to measure the magnetic properties. The cooling method after hot-rolled sheet annealing is 60 ° C /
Seconds. Changes in the crystal grain size of the hot rolled sheet with respect to the annealing temperature of the hot rolled sheet, iron loss of the product, and magnetic flux density of the product are shown in FIGS. 1, 2 and 3, respectively. In the high-purity steel of component 1, the hot rolled sheet annealing temperature is A
Although the hot-rolled crystal structure becomes coarser when the temperature is above the c ₃ point, the hot-rolled crystal structure becomes finer when the annealing temperature of the hot-rolled sheet exceeds the αγ transformation point in the comparative material of component 2.

[0031]

[Table 1]

At the same time, when the hot-rolled sheet annealing temperature is 1000 ° C., the average cooling rate up to 700 ° C. after annealing is changed from 5 ° C. seconds to 100 ° C./second by controlling the steam cooling amount.
The effects of cooling rate on the grain size of hot-rolled sheet, iron loss of the product, and magnetic flux density were investigated. The results are shown in FIGS. 4, 5 and 6, respectively. In the high-purity steel of component 1, the influence of the hot-rolled crystal structure and magnetic properties on the cooling rate after hot-rolled sheet annealing is small, but in the comparative material of component 2, when the cooling rate after hot-rolled sheet annealing is increased, the hot-rolled crystal structure is increased. Became finer and the magnetic characteristics were deteriorated.

As described above, T including C, N and S
A high-purity steel with reduced impurities such as i, V, Nb, and As
c By finishing at a hot-rolled sheet annealing temperature of ₃ points or more, it is possible to reduce iron loss in a product, increase magnetic flux density, and manufacture a non-oriented electrical steel sheet having excellent magnetic properties.

The steel slab composed of the above components is produced in a converter and is produced by continuous casting or ingot-bulking rolling. The steel slab is heated by a known method. This slab is subjected to hot rolling to a predetermined thickness.

The hot-rolled sheet annealing temperature is set to Ac ₃ point or higher. If the hot-rolled sheet annealing temperature is below the Ac ₃ point, the growth of the hot-rolled crystal structure will be insufficient, and a non-oriented electrical steel sheet having excellent magnetic properties cannot be obtained. Therefore, the hot rolled sheet annealing temperature is preferably Ac ₃ point or higher. Although the upper limit of the hot-rolled sheet annealing temperature is not set, the upper limit is naturally determined by the capacity of the annealing furnace and the pickling property. The hot-rolled sheet annealing time is 10 seconds or more and 5 minutes or less, preferably 30 seconds or more and 3 minutes or less. If the annealing time is 10 seconds or less, the effect of annealing is insufficient, and if the annealing time is 5 minutes or more, the effect is saturated and the productivity is lowered, or it causes poor pickling.

In order to investigate the influence of the annealing time of the hot rolled sheet on the magnetic properties of the product, a slab for non-oriented electrical steel having the components and transformation points shown in Table 1 was heated by a usual method and hot rolled. Finished with 2.5mm. The hot-rolled sheet was annealed at 1000 ° C. by changing the soaking time using a continuous annealing furnace, and the hot-rolled sheet was annealed, and the average cooling rate up to 700 ° C. was controlled at 60 ° C./sec. After that, it is pickled and cold rolled to 0.50.
mm. Then, it was annealed at 730 ° C. for 30 seconds in a continuous annealing furnace. Epstein test pieces were cut out from these samples and the magnetic properties were measured. FIG. 7 and FIG. 8 show the relationship between the annealing time of hot-rolled sheet, iron loss, and magnetic flux density, respectively.

As is apparent from FIGS. 7 and 8, excellent magnetic properties are achieved within the range of the hot-rolled sheet annealing time of the present invention. Further, if the hot-rolled sheet annealing time exceeds 5 minutes,
Poor pickling occurred. The measurement results of the Epstein test pieces do not show much deterioration of the magnetic properties, but poor pickling leads to roughening of the steel sheet, and when the non-oriented electrical steel sheet is actually used in a rotating machine, etc. This is not preferable because it leads to a decrease in product ratio and deteriorates performance.

The hot rolled sheet thus obtained is made into a product by one cold rolling and continuous annealing. Further, a skin pass rolling step may be added to obtain a product. If the skin pass rolling ratio is less than 2%, the effect cannot be obtained, and if the skin pass rolling ratio is 20% or more, the magnetic properties are deteriorated.

[0039]

Next, an embodiment of the present invention will be described. [Example 1] A slab for non-oriented electrical steel having the components and transformation points shown in Table 2 was heated by a usual method and hot rolled to a thickness of 2.5 mm. Subsequently, this hot rolled sheet annealing was performed in a continuous annealing furnace. The hot rolled sheet annealing temperature is 1000 ° C,
In any of the component systems, the Ac ₃ point or higher was set. After annealing, the average cooling rate up to 700 ° C was 60 ° C / sec.
Then, it was pickled and finished to 0.50 mm by cold rolling. This was annealed at 730 ° C. for 30 seconds in a continuous annealing furnace. Thereafter, the sample was cut into Epstein samples, and the magnetic properties were measured. Table 2 also shows the components of the present invention and comparative examples and the results of magnetic measurement. By controlling the purity of the steel in this way, it is possible to obtain a material having a high magnetic flux density and a low iron loss value by setting the hot-rolled sheet annealing temperature to Ac ₃ or higher.

[0040]

[Table 2]

Example 2 A slab for non-oriented electrical steel having the components and transformation points shown in Table 3 was heated by a usual method and hot rolled to a thickness of 2.5 mm. The hot rolled sheet was annealed for 30 seconds using a continuous annealing furnace. The annealing temperature is 850 ° C below the Ac ₁ point and 1000 above the Ac ₃ point.
C., and the average cooling rate up to 700.degree. C. was controlled at 60.degree. C./sec. After that, it is pickled and cold rolled to 0.50.
mm and 0.55 mm. A sheet having a thickness of 0.50 mm was annealed at 730 ° C. for 30 seconds in a continuous annealing furnace. Furthermore, it was annealed at 750 ° C. for 2 hours corresponding to the consumer. In addition, a sheet with a thickness of 0.55 mm is 700 ° C in a continuous annealing furnace.
The sheet was annealed for 20 seconds at 20 ° C., finished by skin pass rolling with a reduction rate of 9% to a thickness of 0.50 mm, and annealed at 750 ° C. for 2 hours corresponding to a consumer. Epstein test pieces were cut out from these samples and the magnetic properties were measured. Tables 4 and 5 show the annealing temperature and magnetic measurement results of the hot rolled sheet of the present invention and comparative examples described in the examples.

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

As described above, by setting the annealing temperature of the hot-rolled sheet to the Ac ₃ point or higher, it can be seen that a material having a high magnetic flux density and a low iron loss value can be obtained by both the single pass method and the skin pass rolling method.

Example 3 A slab for non-oriented electrical steel having the components and transformation points shown in Table 6 was heated by a usual method and hot rolled to a thickness of 2.5 mm. This hot-rolled sheet was annealed at a temperature of 1000 ° C. using a continuous annealing furnace to anneal the hot-rolled sheet, and the average cooling rate up to 700 ° C. was 60 ° C.
Controlled to / sec. Then, it was pickled and finished to 0.50 mm by cold rolling. Then in a continuous annealing furnace at 730 ℃
For 30 seconds. Furthermore, it was annealed at 750 ° C. for 2 hours corresponding to the consumer. Epstein test pieces were cut out from these samples and the magnetic properties were measured. Table 7 shows the hot-rolled sheet annealing temperature and magnetic measurement results of the present invention and comparative examples described in the examples.

[0047]

[Table 6]

[0048]

[Table 7]

As shown in Table 7, when the hot rolled sheet annealing time is 10 seconds or less, the growth of the crystal structure of the hot rolled sheet is insufficient and the improvement of the magnetic properties of the product is insufficient. If the hot-rolled sheet annealing time exceeds 5 minutes, poor pickling occurred. Although the Epstein test results do not show much deterioration in magnetic properties, poor pickling leads to roughening of the steel sheet, and the space factor of the iron core laminated when the non-oriented electrical steel sheet is actually used in a rotating machine, etc. Is deteriorated and the performance is deteriorated, which is not preferable. As described above, by setting the annealing time of the hot rolled sheet to 10 seconds or more and 5 minutes or less, it is found that a material having a high magnetic flux density and a low iron loss value can be obtained.

[0050]

As described above, according to the present invention, it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss and excellent magnetic properties.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a hot rolled sheet annealing temperature and a hot rolled sheet crystal grain size.

FIG. 2 is a diagram showing the relationship between hot-rolled sheet annealing temperature and product iron loss.

FIG. 3 is a diagram showing a relationship between a hot rolled sheet annealing temperature and a product magnetic flux density.

FIG. 4 is a diagram showing the relationship between the cooling rate after hot-rolled sheet annealing and the crystal grain size of the hot-rolled sheet.

FIG. 5 is a diagram showing a relationship between a cooling rate after hot-rolled sheet annealing and product iron loss.

FIG. 6 is a diagram showing a relationship between a cooling rate after hot-rolled sheet annealing and a product magnetic flux density.

FIG. 7 is a diagram showing the relationship between hot-rolled sheet annealing time and product iron loss.

FIG. 8 is a diagram showing a relationship between hot-rolled sheet annealing time and product magnetic flux density.

Claims (2)

[Claims] 1. By weight% in steel, 0.10% ≦ Si ≦ 2.50%, C ≦ 0.0025%, N ≦ 0.0020%, S ≦ 0.0020%, Ti ≦ 0.0030 %, Nb ≤ 0.0030%, V ≤ 0.0050%, As ≤ 0.0030%, and the remaining part is Fe and unavoidable impurities. In a method for producing a non-oriented electrical steel sheet, which is a hot-rolled sheet, subjected to hot-rolled sheet annealing and one cold rolling step, and then subjected to finish annealing, hot-rolled sheet annealing is performed for 10 seconds in a temperature range of Ac ₃ points or more. A method for manufacturing a non-oriented electrical steel sheet, which is performed for up to 5 minutes. 2. In the steel, 0.10% ≦ Al ≦ 0.10% ≦ Si ≦ 2.50%, and at least one of Mn and Al, and 0.10% ≦ Al.
≦ 1.00%, 0.10% ≦ Mn ≦ 2.00%, and the total amount of Si and Al is Si + 2Al ≦ 2.50%
C ≦ 0.0025%, N ≦ 0.0020%, S ≦ 0.0020%, Ti ≦ 0.0030%, Nb ≦ 0.0030%, V ≦ 0.0050%, As ≦ 0.0030 %, With the balance being Fe and an unavoidable impurity and having a component having an αγ transformation, hot-rolled into a hot-rolled sheet, subjected to hot-rolled sheet annealing and one cold rolling step, and then A method for producing a non-oriented electrical steel sheet, comprising performing hot-rolled sheet annealing in a temperature range of Ac ₃ or higher for 10 seconds to 5 minutes in the method for producing a non-oriented electrical steel sheet subjected to finish annealing.