JP5671871B2 - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Description

  The present invention relates to a non-oriented electrical steel sheet and a method for producing the same. More specifically, the present invention can be used mainly for stator cores of high-efficiency divided iron core motors such as compressor motors such as air conditioners and refrigerators, drive motors and generators such as electric vehicles and hybrid vehicles. The present invention relates to a suitable non-oriented electrical steel sheet and a method for producing the same.

  Due to the need to reduce greenhouse gases, products with low energy consumption are being developed in the fields of automobiles, home appliances, and the like. For example, in the automobile field, there are low fuel consumption vehicles such as a hybrid drive vehicle combining a gasoline engine and a motor, and a motor drive electric vehicle. In the field of home appliances, there are high-efficiency air conditioners, refrigerators and the like that consume less electricity annually. The technology common to these is a motor, and high efficiency of the motor is an important technology.

  The motors as described above are often multipolar, and it is known that the motor efficiency of the multipolar motor is greatly influenced by the magnetic characteristics of the teeth portion of the stator (stator). In many conventional motors, an integrally punched iron core is used for the stator. In the case of integral punching, the direction of each tooth portion takes various directions with respect to the rolling direction of the electromagnetic steel sheet. For this reason, non-oriented electrical steel sheets having good magnetic properties in the entire circumferential direction have been required for the integrally punched iron core material.

  On the other hand, in recent years, the number of cases in which a split core that is advantageous in terms of winding design and yield is employed for the stator is increasing. In the case of a split iron core, the direction of the tooth portion can be matched with a direction in which the magnetic properties of the electromagnetic steel sheet are good, for example, a rolling direction (hereinafter also referred to as “L direction”).

  Unidirectional electrical steel sheets are known as electrical steel sheets having excellent magnetic properties in the L direction. However, the unidirectional electrical steel sheet is not suitable as a split core material in which a considerable amount of magnetic flux also flows in the C direction because the magnetic properties in the direction perpendicular to the rolling direction (hereinafter also referred to as “C direction”) are extremely poor. Furthermore, in order to manufacture such a unidirectional electrical steel sheet, there is a problem that the manufacturing cost is high because a special facility capable of high-temperature long-time secondary recrystallization annealing and decarburization annealing is required.

Therefore, in Patent Document 1 and Patent Document 2, in order to solve the problem that the magnetic properties in the C direction are poor with respect to the unidirectional electromagnetic steel sheet, a technique related to the electromagnetic steel sheet for the split core in which the iron loss in the C direction is reduced. Is disclosed.
Patent Documents 3 to 5 disclose techniques related to non-oriented electrical steel sheets for split iron cores.

  Conventionally, a two-time cold rolling method is known as a method for enhancing the magnetic properties of a non-oriented electrical steel sheet (see Patent Documents 6 to 9).

JP 2004-100025 A Japanese Patent Laid-Open No. 2004-100026 JP 2008-127600 A JP 2008-127608 A JP 2008-127612 A JP 51-151215 A JP 59-74225 A Japanese Patent Laid-Open No. 11-236618 JP 2000-17330 A

  As described above, in the case of a split iron core, the direction of the tooth portion can be matched with a direction in which the magnetic properties of the electromagnetic steel sheet are good, for example, the rolling direction (L direction). In this case, the direction of the yoke part through which a considerable amount of magnetic flux flows next to the direction of the tooth part coincides with the direction perpendicular to the rolling direction (C direction). The magnetic flux mainly flows in the L direction and the C direction, particularly in the L direction, and hardly flows in the 45 ° direction (hereinafter also referred to as “D direction”) with respect to the rolling direction. Therefore, a non-oriented electrical steel sheet having excellent L-direction magnetic properties and L-direction magnetic properties superior to C-direction magnetic properties is suitable for the split core material. Furthermore, a non-oriented electrical steel sheet having a large value obtained by normalizing the magnetic characteristics obtained by weighted averaging of the L direction and the C direction weighted in the L direction by the average magnetic characteristics in the entire circumferential direction is suitable.

  However, although the electrical steel sheets disclosed in Patent Document 1 and Patent Document 2 are aimed at reducing iron loss in the C direction, it is said that a lower magnetic flux density in the C direction is preferable. However, it is not suitable as a material for a split core through which a considerable amount of magnetic flux flows. In addition, in order to manufacture these electrical steel sheets, similar to the unidirectional electrical steel sheets, special equipment capable of secondary recrystallization annealing and decarburization annealing at a high temperature for a long time is required. have.

  Patent Documents 3 to 5 disclose non-oriented electrical steel sheets for split iron cores, but the relationship between the magnetic characteristics in the L direction and the D direction, or the magnetic characteristics in the C direction and the D direction. Since only the relationship is focused on and the relationship between the magnetic properties in the L direction and the C direction has not been studied, it cannot be said that it is suitable as a non-oriented electrical steel sheet for a split iron core.

  In addition, the non-oriented electrical steel sheet manufacturing methods disclosed in Patent Document 6 and Patent Document 7 are intended to reduce anisotropy, and are disclosed in Patent Document 8 and Patent Document 9. The method for producing a grain-oriented electrical steel sheet is intended to improve simple average magnetic properties in the L direction and the C direction, both of which obtain a non-oriented electrical steel sheet with good circumferential magnetic properties. The purpose is that. Therefore, it cannot be said that it is suitable as a non-oriented electrical steel sheet for a split iron core.

  Thus, the magnetic steel sheet for the split iron core has excellent magnetic properties in the L direction, the magnetic properties in the L direction are superior to the magnetic properties in the C direction, and the L direction and the C direction weighted in the L direction. A non-oriented electrical steel sheet having a large value obtained by standardizing the magnetic properties obtained by weighted average of the values by the average magnetic properties in the entire circumferential direction is suitable, but in the prior art, no detailed study has been made from this viewpoint. Is the actual situation.

  The present invention has been made in view of the above circumstances, and its problem is mainly fixing high-efficiency divided core motors such as compressor motors such as air conditioners and refrigerators, drive motors and generators such as electric vehicles and hybrid vehicles. Suitable for use in a child (stator) iron core, excellent in L direction magnetic properties, L direction magnetic properties superior to C direction magnetic properties, and L direction and C direction weighted in L direction It is an object of the present invention to provide a non-oriented electrical steel sheet having a large value obtained by standardizing the magnetic characteristics obtained by weighted averaging of the above and the average magnetic characteristics in the entire circumferential direction, and a method for manufacturing the same.

  In order to solve the above problems, the present inventors have investigated in detail the magnetic properties in the L direction, the C direction, and the D direction. As a result, the magnetic properties in the L direction are excellent, the magnetic properties in the L direction are superior to those in the C direction, and the magnetic properties obtained by weighted averaging of the L direction weighted in the L direction and the C direction are all around the circumference. In order to obtain a non-oriented electrical steel sheet having a large value normalized by the average magnetic property in the direction, it has been found effective to contain P and increase the anisotropy of the magnetic property. And in order to obtain such magnetic properties, the cold rolling method is adopted twice, and the thickness of the hot rolled steel sheet used for cold rolling, the reduction ratio of cold rolling, the intermediate annealing conditions and the finish annealing conditions are optimized. I found it important to do. The gist of the present invention based on such new findings is as follows.

That is, the present invention relates to mass%, C: 0.005% or less, Si: 1.0% or more and 4.0% or less, Mn: 0.05% or more and 3.0% or less, sol. Al: 0.1% or more and 2.5% or less, P: 0.05% or more and 0.20% or less, S: 0.01% or less and N: 0.01% or less, with the balance being Fe and impurities And having a chemical composition satisfying the following formulas (1) and (2), having a steel structure having an average crystal grain size of 40 μm or more and 180 μm or less, and satisfying the following formulas (3) to (5) There is provided a non-oriented electrical steel sheet having a magnetic property and having a thickness of 0.10 mm to 0.35 mm.
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
Si + 0.5 × sol. Al + 0.3 × Mn + 10 × P ≦ 4.3 (2)
B _50L ≧ 1.700 (3)
B _50L / B _50C ≧ 1.030 (4)
{(2 × B _50L + B _50C ) / 3} / {(B _50L + 2 × B _50D + B _50C ) / 4}
≧ 1.020 (5)
(here,
Si, sol. Al, Mn, P: Content of each element (% by mass)
B _50L : Magnetic flux density (T) in the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50C : Magnetic flux density (T) in the direction perpendicular to the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50D : Magnetic flux density (T) in the direction of 45 ° with respect to the rolling direction when magnetized with a magnetizing force of 5000 A / m.
It is. )

Moreover, this invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A)-(D).
(A) A first cold rolling step (B) of subjecting a hot rolled steel sheet having a thickness of 2.2 mm to 3.5 mm having the above-described chemical composition to cold rolling at a reduction ratio of 10% to 75%. The cold-rolled steel sheet obtained by the first cold rolling step is held in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours, or in a temperature range of 900 ° C. to 1150 ° C. for 1 second or more. Intermediate annealing step for performing intermediate annealing for 600 seconds or less (C) The intermediate annealing steel plate obtained by the intermediate annealing step is subjected to cold rolling at a reduction rate of 50% or more and 85% or less and 0.10 mm or more and 0.35 mm. 2nd cold rolling process (D) which makes the following sheet thickness Finish finishing process which performs finish annealing at 900 to 1200 degreeC to the cold-rolled steel plate obtained by the said 2nd cold rolling process

  The method for producing a non-oriented electrical steel sheet of the present invention is based on box annealing in which the hot-rolled steel sheet to be subjected to the first cold rolling step is held in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours, or In addition, a hot-rolled sheet annealing step of performing hot-rolled sheet annealing by continuous annealing that is held in a temperature range of 900 ° C. or higher and 1150 ° C. or lower for 1 second or more and 600 seconds or less may be provided. This is because the magnetic properties can be further enhanced.

  The non-oriented electrical steel sheet according to the present invention can be expected to improve the motor efficiency of the split iron core type motor. Moreover, since the manufacturing method of the non-oriented electrical steel sheet which concerns on this invention does not require special equipment, it is excellent also in terms of manufacturing cost.

It is a graph which shows the relationship between the rolling reduction of a 1st cold rolling process and a 2nd cold rolling process in an Example, and a magnetic characteristic.

  Hereinafter, the non-oriented electrical steel sheet and the manufacturing method thereof according to the present invention will be described in detail.

A. Non-oriented electrical steel sheet The non-oriented electrical steel sheet of the present invention is, in mass%, C: 0.005% or less, Si: 1.0% to 4.0%, Mn: 0.05% to 3.0% % Or less, sol. Al: 0.1% or more and 2.5% or less, P: 0.05% or more and 0.20% or less, S: 0.01% or less and N: 0.01% or less, with the balance being Fe and impurities And having a chemical composition satisfying the above formulas (1) and (2), a steel structure having an average crystal grain size of 40 μm or more and 180 μm or less, and satisfying the above formulas (3) to (5) And having a thickness of 0.10 mm or more and 0.35 mm or less.

  Hereafter, each structure in the non-oriented electrical steel sheet of this invention is demonstrated in detail.

(Chemical composition)
First, the reason for limiting the chemical composition of the steel sheet will be described. “%” Indicating the content of each element means “mass%” unless otherwise specified.

  C is an element that is contained as an impurity and deteriorates magnetic properties. For this reason, C content shall be 0.005% or less. Preferably, it is 0.003% or less.

  Si is an element effective for increasing the specific resistance of a steel sheet and reducing iron loss. Therefore, the Si content is 1.0% or more. Preferably it is 1.5% or more. On the other hand, when Si is excessively contained, the magnetic flux density is remarkably lowered. For this reason, Si content shall be 4.0% or less. Preferably it is 3.5% or less.

  Al is an element effective for increasing the specific resistance of the steel sheet and reducing iron loss. Therefore, sol. The Al content is 0.1% or more. On the other hand, when it is excessively contained, the magnetic flux density is remarkably lowered. For this reason, sol. The Al content is 2.5% or less. Preferably it is 2.0% or less.

  Mn is an element effective for increasing the specific resistance of the steel sheet and reducing iron loss. Therefore, the Mn content is 0.05% or more. Preferably it is 0.1% or more. On the other hand, if the Mn content is increased, Mn is economically disadvantageous because of its higher alloy cost than Si and Al. For this reason, Mn content shall be 3.0% or less. Preferably it is 2.5% or less.

  P has the effect of improving the texture by improving the texture. Therefore, the P content is 0.05% or more. Preferably it is 0.07% or more. On the other hand, since P is also a solid solution strengthening element, if the P content is excessive, the steel sheet becomes hard and cold rolling becomes difficult. Therefore, the P content is 0.20% or less. Preferably, it is 0.15% or less.

  S is contained as an impurity and combines with Mn in the steel to form fine MnS, inhibits the growth of crystal grains during annealing, and degrades the magnetic properties of the non-oriented electrical steel sheet. For this reason, S content shall be 0.01% or less. Preferably it is 0.005% or less.

  N is contained as an impurity and combines with Al to form fine AlN, which inhibits the growth of crystal grains during annealing and deteriorates magnetic properties. For this reason, N content shall be 0.01% or less. Preferably it is 0.005% or less.

Si, Al and Mn have the effect of increasing the specific resistance and reducing the iron loss as described above. For this reason, the following formula (1) is satisfied with respect to the content of these elements.
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
Here, Si, sol. Al and Mn are content (mass%) of each element.

Si, Al, Mn, and P have the effect of hardening the steel sheet, and if excessively contained, cold rolling becomes difficult. For this reason, the following formula (2) is satisfied with respect to the content of these elements.
Si + 0.5 × sol. Al + 0.3 × Mn + 10 × P ≦ 4.3 (2)
Here, Si, sol. Al, Mn, and P are contents (mass%) of each element.

(Average crystal grain size)
Even if the crystal grain size is too large or too small, the iron loss deteriorates. Therefore, the average crystal grain size is set to 40 μm or more and 180 μm or less.
The average crystal grain size may be the average value of the crystal grain sizes measured by the cutting method in the plate thickness direction and the rolling direction in the longitudinal sectional structure photograph. An optical micrograph can be used as the longitudinal cross-sectional structure photograph. For example, a photograph taken at a magnification of 50 times may be used.

(Magnetic properties)
In the present invention, the magnetic characteristics satisfying the following formulas (3) and (4) are obtained as the magnetic characteristics in the L direction are excellent and the magnetic characteristics in the L direction are superior to those in the C direction. Shall have. In addition, it is preferable that the value of the left side of following formula (4) is 1.035 or more.
Further, the non-oriented electrical steel sheet having a large anisotropy such that a value obtained by normalizing the magnetic characteristics obtained by weighted averaging of the L direction and the C direction weighted in the L direction by the average magnetic characteristics in the entire circumferential direction is increased. It is important to. Therefore, in the present invention, a value obtained by standardizing a magnetic characteristic obtained by weighting the magnetic characteristic in the L direction twice as much as the magnetic characteristic in the C direction by the average magnetic characteristic in the entire circumferential direction is used as an index. It shall have magnetic characteristics satisfying (5).
B _50L ≧ 1.700 (3)
B _50L / B _50C ≧ 1.030 (4)
{(2 × B _50L + B _50C ) / 3} / {(B _50L + 2 × B _50D + B _50C ) / 4}
≧ 1.020 (5)
here,
B _50L : Magnetic flux density (T) in the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50C : Magnetic flux density (T) in the direction perpendicular to the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50D : Magnetic flux density (T) in the direction of 45 ° with respect to the rolling direction when magnetized with a magnetizing force of 5000 A / m.
It is.

(Thickness)
Compressor motors such as air conditioners and refrigerators, drive motors and generators such as electric vehicles and hybrid vehicles are used in the high-speed rotation range. Therefore, non-oriented electrical steel sheets, which are core materials, have low iron loss in the high-frequency range. desirable. A thinner plate thickness is preferable for reducing iron loss under high frequency conditions. Therefore, the plate thickness is 0.35 mm or less. Preferably it is 0.30 mm or less. On the other hand, excessive thinning significantly reduces the productivity of steel plates and motors. Therefore, the plate thickness is 0.10 mm or more. Preferably it is 0.15 mm or more.

(Production method)
The non-oriented electrical steel sheet of the present invention is preferably manufactured by a method for manufacturing a non-oriented electrical steel sheet described later.

B. Manufacturing method of non-oriented electrical steel sheet The manufacturing method of the non-oriented electrical steel sheet of the present invention includes the following steps (A) to (D).
(A) A first cold rolling step (B) of subjecting a hot rolled steel sheet having a thickness of 2.2 mm to 3.5 mm having the above-described chemical composition to cold rolling at a reduction ratio of 10% to 75%. The cold-rolled steel sheet obtained by the first cold rolling step is held in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours, or in a temperature range of 900 ° C. to 1150 ° C. for 1 second or more. Intermediate annealing step for performing intermediate annealing for 600 seconds or less (C) The intermediate annealing steel plate obtained by the intermediate annealing step is subjected to cold rolling at a reduction rate of 50% or more and 85% or less and 0.10 mm or more and 0.35 mm. 2nd cold rolling process (D) which makes the following sheet thickness Finish finishing process which performs finish annealing at 900 to 1200 degreeC to the cold-rolled steel plate obtained by the said 2nd cold rolling process

  Hereinafter, each process in the manufacturing method of the non-oriented electrical steel sheet according to the present invention will be described.

(First cold rolling process)
In the first cold rolling step, cold rolling at a rolling reduction of 10% to 75% is performed on a hot rolled steel sheet having a thickness of 2.2 mm to 3.5 mm.

The thicker the thickness of the hot rolled steel sheet used in the first cold rolling step, the better the magnetic properties. Therefore, the thickness of the hot-rolled steel sheet used for the first cold rolling step is set to 2.2 mm or more . On the other hand, if the thickness of the hot-rolled steel sheet used in the first cold rolling process becomes excessively thick, the cold rolling load may become excessive and cold rolling may be difficult. Therefore, the plate | board thickness of the hot-rolled steel plate used for a 1st cold rolling process shall be 3.5 mm or less. Preferably it is 3.3 mm or less.

  If the rolling reduction in the first cold rolling process is less than 10% or more than 75%, the intended magnetic properties may not be obtained. Therefore, the rolling reduction in the first cold rolling step is set to 10% or more and 75% or less.

Other conditions for cold rolling, such as the temperature of the steel sheet during cold rolling and the diameter of the rolling roll, are not particularly limited, and are appropriately selected depending on the chemical composition of the hot rolled steel sheet, the thickness of the target steel sheet, etc. To do.
A hot-rolled steel sheet is usually subjected to cold rolling after removing the scale formed on the surface of the steel sheet during hot rolling by pickling. As will be described later, when hot-rolled sheet annealing is performed on the hot-rolled steel sheet, it may be pickled either before or after hot-rolled sheet annealing.

(Intermediate annealing process)
In the intermediate annealing step, the cold-rolled steel sheet obtained by the first cold rolling step is held in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours or 900 ° C. to 1150 ° C. Intermediate annealing is performed in the temperature range for 1 second to 600 seconds.
When the annealing temperature in the intermediate annealing step (hereinafter also referred to as “intermediate annealing temperature”) is low or the holding time is insufficient, the crystal grains after the intermediate annealing are not coarsened, so that the target magnetism In some cases, characteristics cannot be obtained. On the other hand, special equipment is required to raise the temperature by intermediate annealing, resulting in an increase in cost. Further, even if the holding time is too long, the effect is saturated, which is disadvantageous in terms of cost. Therefore, in the case of annealing for a long time such as box annealing, it is held in a temperature range of 700 ° C. or more and 900 ° C. or less for 3 hours or more and 40 hours or less, and when annealing is performed for a short time such as continuous annealing. In this case, the temperature is maintained at 900 ° C. or higher and 1150 ° C. or lower for 1 second or more and 600 seconds or less. Intermediate annealing can obtain desired magnetic characteristics in any of the above-described aspects, but when emphasizing magnetic characteristics in the L direction, it is maintained in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours. Is preferred.
Other conditions for the intermediate annealing are not particularly limited.

(Second cold rolling process)
In the second cold rolling step, the intermediate annealed steel sheet obtained by the intermediate annealing step is subjected to cold rolling with a reduction ratio of 50% or more and 85% or less to obtain a plate thickness of 0.10 mm or more and 0.35 mm or less. .
If the rolling reduction in the second cold rolling step is less than 50% or more than 85%, the intended magnetic properties may not be obtained. Therefore, the rolling reduction in the second cold rolling step is set to 50% or more and 85% or less. More preferably, it is 55% or more and 80% or less.
Further, for the reason described in the above-mentioned section “A. Non-oriented electrical steel sheet”, the sheet thickness after the second cold rolling is set to 0.10 mm or more and 0.35 mm or less.
Other conditions for cold rolling, such as the temperature of the steel sheet during cold rolling and the diameter of the rolling roll, are not particularly limited, and are appropriately selected depending on the chemical composition of the steel sheet, the thickness of the target steel sheet, and the like.

(Finish annealing process)
In the finish annealing step, the cold-rolled steel sheet obtained by the second cold rolling step is subjected to finish annealing at 900 ° C. or more and 1200 ° C. or less.
If the annealing temperature in finish annealing (hereinafter also referred to as “finish annealing temperature”) is less than 900 ° C., the average crystal grain size may be less than 40 μm due to insufficient grain growth, and sufficient magnetic properties may not be obtained. On the other hand, if the finish annealing temperature exceeds 1200 ° C., the grain growth proceeds excessively and the average crystal grain size exceeds 180 μm, and sufficient magnetic properties may not be obtained. Furthermore, such high temperature annealing may require special equipment, which may increase costs. Therefore, the finish annealing temperature is set to 900 ° C. or more and 1200 ° C. or less.
Other conditions for finish annealing are not particularly limited.

(Hot rolled annealing)
The hot-rolled steel sheet to be subjected to the first cold rolling process may be subjected to hot-rolled sheet annealing. By performing hot-rolled sheet annealing, better magnetic properties can be obtained.
Hot-rolled sheet annealing may be performed by either box annealing or continuous annealing. When performing by box annealing, it is preferable to hold | maintain in the temperature range of 700 degreeC or more and 900 degrees C or less for 3 hours or more and 40 hours or less. When performing by continuous annealing, it is preferable to hold | maintain in the temperature range of 900 degreeC or more and 1150 degrees C or less for 1 second or more and 600 seconds or less.
Other conditions for hot-rolled sheet annealing are not particularly limited.

(Hot rolling process)
The hot-rolled steel sheet to be subjected to the cold rolling process can be obtained by subjecting a steel ingot or steel slab (hereinafter also referred to as “slab”) having the above chemical composition to hot rolling.
In hot rolling, a steel having the above chemical composition is made into a slab by a general method such as a continuous casting method or a method of rolling a steel ingot, and is charged into a heating furnace and hot rolled. At this time, when the slab temperature is high, hot rolling may be performed without charging the heating furnace.
Various conditions in the hot rolling are not particularly defined, but it is preferable that the finishing temperature is 700 ° C. or higher and the winding temperature is 300 ° C. or higher.

(Other processes)
After the finish annealing step, a coating for applying an insulating film made of only an organic component, only an inorganic component, or an organic-inorganic composite to the surface of the steel sheet may be applied according to a general method. From the viewpoint of reducing the environmental burden, an insulating coating that does not contain chromium may be applied. Further, the coating may be an insulating coating that exhibits adhesive ability by heating and pressing. As a coating material exhibiting adhesive ability, an acrylic resin, a phenol resin, an epoxy resin, a melamine resin, or the like can be used.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be described specifically by way of examples and comparative examples.
A slab having the chemical composition shown in Table 1 below was hot-rolled at a finishing temperature of 800 ° C. and a coiling temperature of 550 ° C. to obtain a hot-rolled steel plate having a thickness of 1.6 mm to 3.0 mm, and pickled. About these pickled steel sheets, with the exception of a part, the first cold rolling process and the second cold rolling process in which the intermediate annealing is sandwiched without subjecting the hot-rolled sheet annealing to a finished sheet thickness of 0.20 mm to 0.35 mm. A rolled steel sheet was used. Some are subjected to hot-rolled sheet annealing by box annealing or continuous annealing, and some of these are finished plate thicknesses by the first cold rolling process and the second cold rolling process that sandwich intermediate annealing under various conditions. The remaining cold-rolled steel sheet was a cold-rolled steel sheet having a finished thickness in one cold rolling process. These cold-rolled steel sheets were subjected to finish annealing that was held at a temperature of 950 ° C. or higher and 1160 ° C. or lower for 10 seconds to obtain non-oriented electrical steel sheets having an average crystal grain size of 55 μm to 152 μm.

With respect to these non-oriented electrical steel sheets, the L-direction magnetic flux density B _50L , the C-direction magnetic flux density B _50C and the D-direction magnetic flux density B _50D when measured with a magnetizing force of 5000 A / m were measured. And it was confirmed whether these magnetic characteristic values satisfy said formula (3)-(5).

  The results are shown in Table 2 together with the production conditions. In addition, FIG. The relationship between the rolling reduction of 1st 10, 16, 17, 19-22 and the 2nd cold rolling process and a magnetic characteristic is shown.

Steel plate No. In Nos. 1 to 10, since the thickness of the hot-rolled steel sheet, the cold rolling reduction ratio, the intermediate annealing conditions, the finish annealing conditions, and the average crystal grain size are within the predetermined ranges, desired magnetic characteristics were obtained. Steel plate No. As shown in FIG. 11, the desired magnetic properties could be obtained even when the intermediate annealing was continuous annealing, but B _50L was a steel plate No. 1 with a rolling reduction equivalent in cold rolling. It was lower than 5. Steel plate No. As shown to 12-15, even if it hot-rolled sheet annealing, the steel plate of the desired magnetic characteristic was able to be obtained.
On the other hand, steel plate No. As shown in FIGS. 16 and 17, the desired magnetic properties could not be obtained when the finished plate thickness was obtained by one cold rolling. Steel plate No. No. 18 is the thickness of the hot-rolled steel plate, Steel plates No. 19 and 20 are steel plate Nos. For Nos. 21 and 22, the reduction ratio in the second cold rolling step was outside the predetermined range, so that the desired magnetic properties could not be obtained.

Claims (4)

In mass%, C: 0.005% or less, Si: 1.0% or more and 4.0% or less, Mn: 0.05% or more and 3.0% or less, sol. Al: 0.1% or more and 2.5% or less, P: 0.05% or more and 0.20% or less, S: 0.01% or less and N: 0.01% or less, with the balance being Fe and impurities And having a chemical composition satisfying the following formulas (1) and (2):
Having a steel structure with an average crystal grain size of 40 μm or more and 180 μm or less,
Having magnetic properties satisfying the following formulas (3) to (5):
A non-oriented electrical steel sheet for a split iron core having a thickness of 0.10 mm to 0.35 mm.
Si + sol. Al + 0.5 × Mn ≧ 2.0 (1)
Si + 0.5 × sol. Al + 0.3 × Mn + 10 × P ≦ 4.3 (2)
B _50L ≧ 1.700 (3)
B _50L / B _50C ≧ 1.030 (4)
{(2 × B _50L + B _50C ) / 3} / {(B _50L + 2 × B _50D + B _50C ) / 4}
≧ 1.020 (5)
(here,
Si, sol. Al, Mn, P: Content of each element (% by mass)
B _50L : Magnetic flux density (T) in the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50C : Magnetic flux density (T) in the direction perpendicular to the rolling direction when magnetized with a magnetizing force of 5000 A / m
B _50D : Magnetic flux density (T) in the direction of 45 ° with respect to the rolling direction when magnetized with a magnetizing force of 5000 A / m.
It is. )   The non-oriented electrical steel sheet for a split iron core according to claim 1, wherein the non-oriented electrical steel sheet has a magnetic property satisfying the following formula (6).
  B _50D ≦ 1.630 (6) A method for producing a non-oriented electrical steel sheet for a split iron core comprising the following steps (A) to (D):
(A) 1st cold rolling which performs the cold rolling by the reduction rate of 10% or more and 75% or less to the hot rolled steel plate of thickness 2.2mm or more and 3.5mm or less which has the chemical composition described in Claim 1 Process;
(B) The cold-rolled steel sheet obtained by the first cold rolling step is held in a temperature range of 700 ° C. to 900 ° C. for 3 hours to 40 hours, or in a temperature range of 900 ° C. to 1150 ° C. An intermediate annealing step for performing an intermediate annealing for 1 second or more and 600 seconds or less;
(C) A second cold rolling step in which the intermediate annealed steel sheet obtained by the intermediate annealing step is subjected to cold rolling at a reduction ratio of 50% or more and 85% or less to obtain a plate thickness of 0.10 mm or more and 0.35 mm or less. And (D) a finish annealing step of subjecting the cold-rolled steel sheet obtained by the second cold rolling step to finish annealing at 900 ° C. or more and 1200 ° C. or less. The hot-rolled steel sheet to be subjected to the first cold rolling step is subjected to box annealing for 3 to 40 hours in a temperature range of 700 ° C. or more and 900 ° C. or less, or in a temperature range of 900 to 1150 ° C. for 1 second. The method for producing a non-oriented electrical steel sheet for a split core according to claim 3 , further comprising a hot-rolled sheet annealing step for performing hot-rolled sheet annealing by continuous annealing for 600 seconds or less.

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