JP5447167B2 - 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 is suitable for a stator core of a highly efficient divided core motor such as a compressor motor such as an air conditioner or a refrigerator, a drive motor such as an electric vehicle or a hybrid vehicle, or a generator. The present invention relates to a non-oriented electrical steel sheet having good magnetic properties 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. These common technologies are motors, and high efficiency of the motors is an important technology.

In many conventional motors, the stator uses an integrally punched iron core. As a core material for such a motor, a non-oriented electrical steel sheet with low anisotropy and good magnetic properties in all directions is required. Has been.
On the other hand, in recent years, the number of cases in which a split core that is advantageous in terms of winding design is adopted for the stator is increasing. As a core material of such a motor, a rolling direction (hereinafter also referred to as “L direction”) is used. The non-oriented electrical steel sheet having good magnetic properties is required.

  By the way, there is a grain-oriented electrical steel sheet as an electrical steel sheet having good magnetic properties in the L direction. However, the grain-oriented electrical steel sheet is not suitable as a motor core material in which magnetic flux flows in the C direction because the magnetic properties in the rolling vertical direction (hereinafter also referred to as “C direction”) are extremely poor.

  Thus, Patent Document 1 discloses a non-oriented electrical steel sheet for a split iron core, in which the iron loss in the L direction is equivalent to that of the directional electrical steel sheet, and the iron loss in the C direction is lower than that of the directional electrical steel sheet. Techniques related to this are disclosed. However, in order to manufacture such a non-oriented electrical steel sheet, special equipment capable of secondary recrystallization annealing and decarburization annealing at a high temperature for a long time is required.

Japanese Patent Laid-Open No. 2004-100026

  The present invention has been made in view of the above-described problems, and is a stator (stator) of a high-efficiency divided iron core motor such as a compressor motor such as an air conditioner or a refrigerator, a drive motor or a generator such as an electric vehicle or a hybrid vehicle. An object of the present invention is to provide a non-oriented electrical steel sheet suitable for an iron core and having good magnetic properties in the rolling direction and a method for producing the same.

In order to solve the above-mentioned problems, the present inventors have intensively studied to obtain a non-oriented electrical steel sheet having particularly excellent L-direction magnetic properties and excellent C-direction magnetic properties. As a result, in the manufacturing process of the non-oriented electrical steel sheet, the first cold rolling process, the intermediate annealing process, the second cold rolling process, and the finish annealing process are sequentially performed, and the first cold rolling process and the second cold rolling process are performed. By optimizing the rolling reduction ratio in the process and the annealing conditions in the intermediate annealing process and the finish annealing process, it is possible to obtain a non-oriented electrical steel sheet having particularly excellent L-direction magnetic properties and good C-direction magnetic properties. I found out that it would be possible. It was also found that by adding a proper amount of Si, Al, and Mn in combination, thinning the plate thickness, and controlling the average crystal grain size appropriately, good magnetic properties in the L and C directions can be obtained. .
The present invention has been made on the basis of the above new findings, and the gist thereof 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, sol. Al: less than 2.5%, Mn: 0.1% or more and 3.0% or less, P: 0.2% or less, S: 0.005% or less and N: 0.005% or less, the balance being Fe and impurities, and Si and sol. The total content of Al is less than 4.5%, the plate thickness is 0.10 mm or more and 0.35 mm or less, the average crystal grain size is 30 μm or more and 200 μm or less, and the following formula (1) The non-oriented electrical steel sheet is characterized in that the X value defined by is 0.845 or more, the iron loss W _{10 / 1k} when excited at a magnetic flux density of 1.0 T and a frequency of 1 kHz is 80 W / kg or less. I will provide a.
X = (2 × B _50L + B _50C ) / (3 × Is) (1)
(B _50L is the magnetic flux density in the rolling direction when magnetized with a magnetizing force of 5000 A / m, B _50C is the magnetic flux density in the direction perpendicular to the rolling when magnetized with a magnetizing force of 5000 A / m, and Is is the spontaneous magnetization at room temperature. is there.)

  In the above invention, the chemical composition contains one or two selected from the group consisting of Sn: 0.1% by mass or less and Sb: 0.1% by mass or less, instead of a part of the Fe. You may do it. This is because the texture can be improved by improving the texture of the non-oriented electrical steel sheet.

  In the present invention, the chemical composition may contain Ca: 0.01% by mass or less in place of part of the Fe. This is because the crystal characteristics can be improved and the magnetic properties can be improved.

This invention provides the manufacturing method of the non-oriented electrical steel sheet characterized by having the following process (A)-(D).
(A) 1st cold rolling process which cold-rolls the hot-rolled steel plate which has the above-mentioned chemical composition at a reduction rate of 10% or more and 75% or less (B) Cold rolling obtained by the first cold rolling process Intermediate annealing step for subjecting the steel sheet to intermediate annealing for holding for 1 hour to 40 hours in a temperature range of 700 ° C. to 900 ° C. (C) Reduction of 50% to 85% to the intermediate annealing steel plate obtained by the intermediate annealing step Second cold rolling step (D) to obtain a sheet thickness of 0.10 mm or more and 0.35 mm or less by performing cold rolling at a rate of 900 ° C. or more and 1200 ° C. on the cold rolled steel sheet obtained by the second cold rolling step Finish annealing process for finishing annealing in the following temperature range

  In the above invention, the hot-rolled steel sheet to be subjected to the first cold rolling step is subjected to a box annealing that is held in a temperature range of 700 ° C. to 900 ° C. for 1 hour to 20 hours or 900 ° C. to 1100 ° C. You may have the hot-rolled sheet annealing process which performs hot-rolled sheet annealing by the continuous annealing hold | maintained in a temperature range for 1 second or more and 180 seconds or less. This is because the magnetic properties can be further enhanced.

  In the present invention, improvement in motor efficiency of the split iron core motor can be expected. Further, in the present invention, since no special equipment is required, the manufacturing cost is excellent.

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

  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 mass%, C: 0.005% or less, Si: 1.0% or more and 4.0% or less, sol. Al: less than 2.5%, Mn: 0.1% or more and 3.0% or less, P: 0.2% or less, S: 0.005% or less and N: 0.005% or less, the balance being Fe and impurities, and Si and sol. The total content of Al is less than 4.5%, the plate thickness is 0.10 mm or more and 0.35 mm or less, the average crystal grain size is 30 μm or more and 200 μm or less, and the following formula (1) The X value defined by the above is 0.845 or more, and the iron loss W _{10 / 1k} when excited at a magnetic flux density of 1.0 T and a frequency of 1 kHz is 80 W / kg or less.
X = (2 × B _50L + B _50C ) / (3 × Is) (1)
(B _50L is the magnetic flux density in the rolling direction when magnetized with a magnetizing force of 5000 A / m, B _50C is the magnetic flux density in the direction perpendicular to the rolling when magnetized with a magnetizing force of 5000 A / m, and Is is the spontaneous magnetization at room temperature. is there.)

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

(Chemical composition)
First, the reasons for limiting the chemical composition of the non-oriented electrical steel sheet of the present invention 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. Therefore, the C content is 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. On the other hand, when it is excessively contained, the magnetic flux density is remarkably lowered. Therefore, the Si content is 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 the iron loss. However, when it is excessively contained, the magnetic flux density is remarkably lowered. For this reason, sol. The Al content is less than 2.5%. In order to obtain the effect of the above action more reliably, the sol. The Al content is preferably 0.1% or more.

  Here, since Si and Al have high solid solution strengthening ability, if they are excessively contained, cold rolling becomes difficult. Therefore, Si and sol. The total content of Al is less than 4.5%.

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

  P is an element generally contained as an impurity. However, P has an effect of improving the magnetic properties by improving the texture of the non-oriented electrical steel sheet, and therefore may be positively contained. However, 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 0.2% or less. In order to more reliably obtain the effect of the above action, the P content is preferably set to 0.015% or more.

  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 0.005% or less. Preferably it is 0.003% 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 0.005% or less. Preferably it is 0.003% or less.

  Sn and Sb may be contained because they have the effect of improving the texture of the non-oriented electrical steel sheet by improving the texture. However, if excessively contained, the magnetic properties are deteriorated. For this reason, content of Sn and Sb shall be 0.1% or less, respectively. In order to more reliably obtain the effect of the above action, it is preferable to contain any element by 0.01% or more.

  Ca is an element effective for inclusion control, and when added appropriately, has the effect of improving crystal grain growth and improving magnetic properties. However, if it is excessively contained, the effect of the above action is saturated and the cost is increased. Therefore, the Ca content is 0.01% or less. In order to more reliably obtain the effect of the above action, the Ca content is preferably 0.0003% or more.

(Magnetic properties)
Regarding the magnetic flux density, in the case of a split iron core, the L direction is more important than the C direction. Therefore, the X value defined by the following formula (1) is 0.845 or more.
X = (2 × B _50L + B _50C ) / (3 × Is) (1)
Here, B _50L is the magnetic flux density in the rolling direction when magnetized at a magnetizing force of 5000 A / m, B _50C is the magnetic flux density in the direction perpendicular to the rolling when magnetized at a magnetizing force of 5000 A / m, and Is is the spontaneous magnetization at room temperature. .
Is is obtained by the following formulas (2) and (3). In addition, Formula (2) calculates | requires spontaneous magnetization on the assumption that the spontaneous magnetization of a steel plate is simply diluted with elements other than Fe. Moreover, what is necessary is just to measure the density of the steel plate in Formula (2) according to JISZ8807.
Is = 2.16 × {(density of steel plate) / (density of Fe)} × [Fe content (% by mass)] / 100 (2)
Fe content (% by mass) = 100 (% by mass) − [C, Si, Mn, sol. Total content (mass%) of Al, P, S, N, Sn, Sb, Ca] (3)

Furthermore, with regard to iron loss, compressor motors such as air conditioners and refrigerators, drive motors such as electric vehicles and hybrid vehicles, and high-efficiency divided iron core motors such as generators are often used in the high-speed rotation range. Lower iron loss is required. Therefore, the iron loss W _{10 / 1k} when excited at a magnetic flux density of 1.0 T and a frequency of 1 kHz is 80 W / kg or less. Preferably it is 70 W / kg or less.

(Average crystal grain size)
As mentioned above, compressor motors such as air conditioners and refrigerators, drive motors such as electric vehicles and hybrid vehicles, and high-efficiency divided core motors such as generators are often used in high-speed rotation regions. Low iron loss is required. Even if the crystal grain size is too large or too small, the iron loss under high frequency conditions deteriorates, so the average crystal grain size is set to 30 μm or more and 200 μm or less.

  Here, the average crystal grain size may be an average value of crystal grain sizes measured by a cutting method in the plate thickness direction and the rolling direction in the longitudinal cross-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.

(Thickness)
In order to reduce the iron loss under high frequency conditions, the thinner the plate thickness, the better. Therefore, the plate thickness is set to 0.35 mm or less. Preferably it is 0.30 mm or less. On the other hand, excessively thinning significantly reduces the productivity of steel plates and motors, so the plate thickness is set to 0.10 mm or more. Preferably, it is 0.15 mm or more.

(Production method)
The non-oriented electrical steel sheet having the above magnetic properties is preferably manufactured by a method for manufacturing a non-oriented electrical steel sheet described later.

B. The manufacturing method of a non-oriented electrical steel sheet The manufacturing method of the non-oriented electrical steel sheet of this invention has the following process (A)-(D), It is characterized by the above-mentioned.
(A) 1st cold rolling process which cold-rolls the hot-rolled steel sheet which has the above-mentioned chemical composition at a reduction rate of 10% or more and 75% or less (B) The cold-rolled steel sheet obtained by the 1st cold rolling process An intermediate annealing step (C) in which intermediate annealing is performed in which the intermediate annealing is performed in a temperature range of 700 ° C. to 900 ° C. for 1 hour to 40 hours. The rolling reduction of 50% to 85% Second cold rolling step (D) in which cold rolling is performed to obtain a sheet thickness of 0.10 mm or more and 0.35 mm or less. Temperature of 900 ° C. or more and 1200 ° C. or less on the cold rolled steel sheet obtained by the second cold rolling step. Finish annealing process for finishing annealing in the area

  Hereinafter, each process in the manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated.

(First cold rolling process)
In the first cold rolling step, the hot rolled steel sheet having the above chemical composition is subjected to cold rolling at a rolling reduction of 10% to 75%.
If the rolling reduction in the first cold rolling step is less than 10% or more than 75%, the intended magnetic characteristics 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 subjected to intermediate annealing that is maintained in a temperature range of 700 ° C. to 900 ° C. for 1 hour to 40 hours.
If the intermediate annealing temperature in the intermediate annealing step is less than 700 ° C., or if the time for holding in the temperature range of 700 ° C. or more is less than 1 hour, the intended magnetic characteristics may not be obtained. On the other hand, special equipment is required to set the intermediate annealing temperature to over 900 ° C, and the effect will be saturated even if the time for holding in the temperature range of 700 ° C or higher exceeds 40 hours. Invite. Therefore, the intermediate annealing step is held in a temperature range of 700 ° C. or more and 900 ° C. or less for 1 hour or more and 40 hours or less.
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.

  As described in the section “A. Non-oriented electrical steel sheet” above, it is preferable that the plate thickness is thin in order to reduce the iron loss under high frequency conditions, while excessive thinning is the productivity of the steel plate and the motor. The plate thickness is 0.10 mm or more and 0.35 mm or less, preferably 0.15 mm or more and 0.30 mm or less. The plate thickness is 0.10 mm or more.

  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 that is maintained in a temperature range of 900 ° C. or more and 1200 ° C. or less.
If the finish annealing temperature in the finish annealing process is less than 900 ° C., the average crystal grain size may be less than 30 μm due to insufficient grain growth, and sufficient magnetic properties may not be obtained. Therefore, the finish annealing temperature is 900 ° C. or higher. On the other hand, if the finish annealing temperature exceeds 1200 ° C., the grain growth proceeds excessively and the average crystal grain size exceeds 200 μm, and sufficient magnetic properties may not be obtained. Therefore, finish annealing temperature shall be 1200 degrees C or less.
The finish annealing time to be maintained in the temperature range of 900 ° C. or more and 1200 ° C. or less is not particularly limited, but is preferably 1 second or more in order to obtain good magnetic properties more reliably. On the other hand, from the viewpoint of productivity, the finish annealing time is preferably set to 120 seconds or less.
Other conditions for finish annealing are not particularly limited.

(Hot rolled sheet annealing process)
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 1 hour or more and 20 hours or less. When performing by continuous annealing, it is preferable to hold | maintain for 1 second or more and 180 second or less in the temperature range of 900 degreeC or more and 1100 degrees C or less.
Other conditions for hot-rolled sheet annealing are not particularly limited.

(Hot rolling process)
The hot-rolled steel sheet used for the first cold rolling step 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 for hot rolling are not particularly limited.

(Other processes)
You may perform the coating process which apply | coats the insulating film which consists only of an organic component, only an inorganic component, or an organic inorganic composite to the steel plate surface according to the general method after the said finish annealing process. From the viewpoint of reducing environmental burden, an insulating film not containing chromium may be applied. Further, the coating process may be a process of applying an insulating coating that exhibits adhesive ability by heating and pressurizing. 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 non-oriented electrical steel sheet manufactured according to the present invention is the same as that described in the above-mentioned section “A. Non-oriented electrical steel sheet”, and thus the description thereof is omitted here.

  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 into a hot rolled steel sheet having a thickness of 2.0 mm to 2.3 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 intermediate annealing is sandwiched without subjecting hot rolled sheet annealing, the finished sheet thickness is 0.20 mm to 0.50 mm. A rolled steel sheet was used. A part of the steel sheet is subjected to hot-rolled sheet annealing by box annealing at 800 ° C. for 10 hours or continuous annealing at 950 ° C. for 20 seconds, and the thickness of the finished sheet is reduced by the first cold rolling process and the second cold rolling process to sandwich the intermediate annealing. A cold-rolled steel sheet was obtained. The remainder was subjected to hot-rolled sheet annealing by box annealing at 900 ° C. for 10 hours to obtain a cold-rolled steel sheet having a finished sheet thickness by a single 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 1180 ° C. or lower for 30 seconds to obtain non-oriented electrical steel sheets having an average crystal grain size of 51 μm to 162 μm.

For these non-oriented electrical steel sheets, the iron loss W _{10 / 1k} when magnetized at a magnetic flux density of 1.0 T and a frequency of 1 kHz, and the magnetic flux density B _50L and C direction in the L direction when magnetized at a magnetizing force of 5000 A / m. The magnetic flux density _B50C was measured. The X value was calculated by substituting B _50L and B _50C into the above equation (1). The results are shown in Table 2 below together with the production conditions. FIG. 1 shows the relationship between the reduction ratio and the X value in the first cold rolling process and the second cold rolling process.

  No. 1 to 5 and 11 to 20 have desired reduction in magnetic properties because the reduction ratio, finished plate thickness, and average grain size in the first cold rolling step and the second cold rolling step are within the predetermined ranges. Yes. No. As shown to 18-20, the magnetic characteristic improved by giving hot-rolled sheet annealing. On the other hand, no. No. 6 has a finishing plate thickness outside the predetermined range. No. 7 was not subjected to cold rolling twice with intermediate annealing, so In Nos. 8 and 9, since the rolling reduction and finished plate thickness in the second cold rolling process are out of the predetermined ranges, No. 10 has a reduction ratio in the first cold rolling step that is out of the predetermined range, and thus none of the desired magnetic properties can be obtained.

Claims (6)

In mass%, C: 0.005% or less, Si: 1.0% or more and 4.0% or less, sol. Al: less than 2.5%, Mn: 0.1% or more and 3.0% or less, P: 0.08 % or less, S: 0.005% or less and N: 0.005% or less, the balance being Fe and impurities, and Si and sol. The total content of Al is less than 4.5%, the plate thickness is 0.10 mm or more and 0.35 mm or less, the average crystal grain size is 30 μm or more and 200 μm or less, and the following formula (1) The non-oriented electrical steel sheet is characterized in that the X value defined by is 0.845 or more, the iron loss W _{10 / 1k} when excited at a magnetic flux density of 1.0 T and a frequency of 1 kHz is 80 W / kg or less. .
X = (2 × B _50L + B _50C ) / (3 × Is) (1)
(B _50L is the magnetic flux density in the rolling direction when magnetized with a magnetizing force of 5000 A / m, B _50C is the magnetic flux density in the direction perpendicular to the rolling when magnetized with a magnetizing force of 5000 A / m, and Is is the spontaneous magnetization at room temperature. is there.)   The chemical composition contains one or two selected from the group consisting of Sn: 0.1% by mass or less and Sb: 0.1% by mass or less instead of part of the Fe. The non-oriented electrical steel sheet according to claim 1.   The non-oriented electrical steel sheet according to claim 1 or 2, wherein the chemical composition contains Ca: 0.01 mass% or less instead of a part of the Fe. The non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the plate thickness is 0.30 mm or less. Possess the following steps (A) ~ (D), a method for producing a non-oriented electrical steel sheet that does not perform secondary recrystallization annealing,
The non-oriented electrical steel sheet has an average crystal grain size and magnetic properties satisfying the conditions according to claim 1 :
(A) A first cold rolling step in which hot rolling steel sheet having the chemical composition described in any one of claims 1 to 3 is subjected to cold rolling at a reduction rate of 10% to 75%. ;
(B) An intermediate annealing step for subjecting the cold-rolled steel sheet obtained by the first cold rolling step to an intermediate annealing for holding in a temperature range of 700 ° C. to 900 ° C. for 1 hour to 40 hours;
(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 a finish annealing to be held in a temperature range of 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 a box annealing that is held in a temperature range of 700 ° C. or more and 900 ° C. or less for 1 hour or more and 20 hours or less, or in a temperature range of 900 ° C. or more and 1100 ° C. or less for 1 second. The method for producing a non-oriented electrical steel sheet according to claim 5, further comprising a hot-rolled sheet annealing step for performing hot-rolled sheet annealing by continuous annealing that is maintained for 180 seconds or less.

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