TWI682039B - Non-oriented electrical steel sheet and method for manufacturing thereof - Google Patents

Abstract

A non-oriented electrical steel sheet includes a silicon steel and an insulation coating. The silicon steel includes Si, Al, and Mn as a chemical composition. In a central area along a thickness direction of the silicon steel, a degree of {5 5 7}＜7 14 5＞ orientation development is 12 to 35.

Description

Non-directional electromagnetic steel plate and manufacturing method thereof

The present invention relates to a non-oriented electrical steel sheet excellent in magnetic properties and punching workability and a method for manufacturing the same.

Background of the Invention In recent years, especially in the field of electrical equipment such as rotating machines, small and medium-sized transformers, and electronic components, among the global trends of power saving, energy saving, and reduction of CO ₂ emissions, the trend of protecting the global environment is represented. The demand for higher efficiency and miniaturization of motors is increasing day by day. Under such a social environment, the non-oriented electromagnetic steel sheet used as the core material of the motor is required to improve its performance.

For example, in the automotive field, non-oriented electromagnetic steel plates are used as iron cores of drive motors for hybrid drive vehicles (HEV: Hybrid Electric Vehicle). The drive motors used in HEVs, due to the limitation of installation space and the reduction in fuel consumption achieved by the reduction in weight, increase the demand for miniaturization.

In order to miniaturize the drive motor, it is necessary to increase the motor torque. Therefore, for non-oriented electrical steel sheets, it is required to further increase the magnetic flux density. In addition, because the capacity of the battery installed in the car is limited, it is necessary to reduce the energy loss of the motor. Therefore, it is required to further reduce the iron loss of the non-oriented electrical steel sheet.

In addition, among the motor cores using non-directional electromagnetic steel plates, there are, for example, the so-called "split cores", in which the cores divided into individual teeth are wound and wound, and then the cores are assembled with each other to form a stator The final form of the iron core.

Split iron cores are mostly used in iron cores with complex shapes, which require high precision for the shape of components. However, in order to reduce the iron loss, the electromagnetic steel sheet that has undergone sufficient heat treatment to coarsen the crystal grains also becomes soft. Therefore, when the member (steel blank) is punched, the shape accuracy may be reduced.

Regarding the reduction in shape accuracy, for example, Patent Documents 1 to 3 disclose a technique for improving punching accuracy by hardening a steel plate or refining crystal grains. However, although these technologies may also improve the punching accuracy, the magnetic characteristics such as magnetic flux density and iron loss cannot be fully satisfied in recent years.

Prior technical literature Patent Literature Patent Literature 1: International Publication No. 2003/002777 Patent Document 2: Japanese Patent Laid-Open No. 2003-197414 Patent Document 3: Japanese Patent Laid-Open No. 2004-152791

Summary of the invention Problems to be solved by invention In the prior art, no technology has been established that can balance punching accuracy and magnetic characteristics. As a non-oriented electromagnetic steel plate for split iron core, if the punching precision and magnetic characteristics can be taken into account, it can respond to the demand for higher efficiency and miniaturization of the motor using the split iron core.

The present invention is directed to dividing a core, improving the machining accuracy (punching processability) at the time of punching, and having excellent magnetic characteristics. In particular, the present invention has the problem that it is excellent in punching workability and, at the same time, is used as a motor core, and also has excellent magnetic properties in both the rolling direction and the sheet width direction. That is, an object of the present invention is to provide a non-oriented electrical steel sheet excellent in punching workability and magnetic properties and a method for manufacturing the same.

Means to solve the problem The present inventors conducted in-depth discussions on methods for solving the above-mentioned problems. As a result, it was found that if the concentration of {5 5 7}<7 14 5> azimuth is increased in the center region of the base material steel plate, both the punching workability and the magnetic properties can be improved.

Therefore, the present inventors conducted detailed studies on the conditions for increasing the degree of concentration of {5 5 7}<7 14 5> azimuth in the central area in the plate thickness direction. It was found that as long as each step is controlled to control the ratio of the recrystallized structure to the unrecrystallized structure in the steel sheet before cold rolling, it can be increased in the central area in the thickness direction after subsequent cold rolling and finish annealing{ 5 5 7}<7 14 5> The degree of azimuth concentration.

The gist of the present invention is as follows.

(1) The non-oriented electrical steel sheet according to the aspect of the present invention includes a silicon steel sheet and an insulating coating; the composition of the silicon steel sheet includes: in mass %, Si: 0.01~3.50%, Al: 0.001~2.500%, Mn: 0.01~3.00%, C: 0.0030% or less, P: 0.180% or less, S: 0.003% or less, N: 0.003% or less, B: 0.002% or less, Sb: 0~0.05%, Sn: 0~0.20%, Cu : 0~1.00%, REM: 0~0.0400%, Ca: 0~0.0400% and Mg: 0~0.0400%, and the remaining part is composed of Fe and impurities; and the center area of the silicon steel plate in the thickness direction {5 5 7}<7 14 5> The degree of azimuth concentration is 12 or more and 35 or less. (2) In the non-oriented electrical steel sheet of (1) above, the aforementioned composition of the silicon steel sheet may also contain at least one of the following elements: in mass %, Sb: 0.001 to 0.05%, Sn: 0.01 to 0.20% , Cu: 0.10~1.00%, REM: 0.0005~0.0400%, Ca: 0.0005~0.0400% and Mg: 0.0005~0.0400%. (3) In the non-oriented electrical steel sheet of (1) or (2) above, the degree of aggregation in the {5 5 7}<7 14 5> orientation may be 18 or more and 35 or less. (4) A method for manufacturing a non-oriented electrical steel sheet according to an aspect of the present invention is to manufacture a non-oriented electrical steel sheet as described in any one of (1) to (3) above, the method comprising: a casting step, hot rolling Steps, heat preservation treatment steps, pickling steps, cold rolling steps, finish annealing steps and film forming steps; casting steel embryos in the casting step, the composition of the steel embryos contains: in mass%, Si: 0.01~3.50% , Al: 0.001~2.500%, Mn: 0.01~3.00%, C: 0.0030% or less, P: 0.180% or less, S: 0.003% or less, N: 0.003% or less, B: 0.002% or less, Sb: 0~0.05 %, Sn: 0~0.20%, Cu: 0~1.00%, REM: 0~0.0400%, Ca: 0~0.0400% and Mg: 0~0.0400%, and the remaining part is composed of Fe and impurities; hot rolling In the extension step, the heating temperature of the steel blank before hot rolling is set to 1000 to 1300°C, the final rolling temperature at the completion of hot rolling is set to 800 to 950°C, and the cumulative reduction rate of hot rolling delay is set to 98 to 99.5 %, the average cooling rate from the end temperature of hot rolling to the holding temperature of the holding process is set to 80~200℃/sec; in the holding process step, the holding temperature is set to 700~850℃, and the holding time is set to 10 ~180 minutes, and the unrecrystallized fraction of the steel plate before the cold rolling step is controlled to 10~20 area%; in the cold rolling step, the cumulative rolling reduction rate of the cold rolling delay is set to 80~95%; In the finishing annealing step, the average heating rate from the starting temperature to 750°C is set to 5 to 50°C/sec, and the average heating rate from 750°C to the soaking temperature for finishing annealing is 20 to 100 Within the range of ℃/second, the temperature was changed to a faster temperature increase rate than the above average temperature increase rate up to 750° C., and the soaking temperature of the finish annealing was set to be higher than the recrystallization temperature.

Invention effect According to the above aspect of the present invention, in addition to punching workability, it is possible to provide a non-oriented electrical steel sheet excellent in magnetic properties in both the rolling direction and the sheet width direction in addition to punching workability and a method for manufacturing the same .

Embodiment of the invention The preferred embodiments of the present invention will be described in detail below. However, the present invention is not limited to the configuration disclosed in this embodiment, and various changes can be made without departing from the gist of the present invention. In addition, the following numerical value limits the range, and the lower limit and the upper limit are included in the range. The value displayed as "greater than" or "less than" is not included in the value range. "%" related to the content of each element means "mass %".

The non-oriented electromagnetic steel sheet of this embodiment includes a silicon steel sheet as a base material steel sheet and an insulating coating. FIG. 1 is a schematic cross-sectional view showing a non-oriented electrical steel sheet according to this embodiment. When viewed in a cross-section parallel to the cutting direction and the thickness direction, the non-oriented electrical steel sheet 1 of this embodiment includes a silicon steel sheet 3 and an insulating coating 5. In addition, in this embodiment, in the central region of the silicon steel sheet in the thickness direction, the degree of {5 5 7}<7 14 5> azimuth aggregation is 12 or more.

(Assembly organization of silicon steel plate) In this embodiment, in the central region of the silicon steel sheet in the thickness direction, the degree of concentration of {5 5 7}<7 14 5> azimuth must be controlled to 12 or more.

Moreover, in this embodiment, for example, {1 1 1}<1 1 2> azimuth and {5 5 7}<7 14 5> azimuth, etc., Miller for the normal direction of the rolled surface (rolled surface direction) The index and the Miller index in the direction parallel to the rolling direction (inward direction of the rolling plane) are set to include directions within ±5° each.

{5 5 7}<7 14 5> The azimuth is closer to the {1 1 1} azimuth which is suitable for improving the machining accuracy during punching, and is also closer to the {4 1 1} which is suitable for improving the magnetic characteristics <1 4 8> The bearing of the bearing. Therefore, in the central area of the silicon steel sheet in the thickness direction, if the degree of {5 5 7}<7 14 5> orientation is increased, both the punching workability and the magnetic properties can be improved.

{5 5 7}<7 14 5> When the azimuth concentration is 12 or more, both the punching workability and magnetic properties can be improved. And it should be above 15 and more preferably above 18. On the other hand, since the degree of {5 5 7}<7 14 5> orientation is as high as possible, the upper limit is not particularly limited. However, since it is practically difficult to increase the degree of aggregation of {5 5 7}<7 14 5> azimuth above 35, the upper limit may be set to 35 or less. The upper limit may be 30 or less, or 25 or less.

The method for increasing the concentration of {5 5 7}<7 14 5> orientation in the central area of the silicon steel sheet in the thickness direction will be described later.

The degree of aggregation of crystal orientation can be determined by the following method. Let the thickness of the silicon steel plate be t, and define the position from the surface of the silicon steel plate toward the thickness direction of 1/2t as the central area. In addition, the surface of the test piece of about 30 mm×30 mm cut from the steel plate is mechanically polished to reduce the thickness and expose the center area. Chemical polishing and electrolytic polishing were performed on this exposed surface to remove strain, and a test piece for measurement was prepared.

The test piece for measurement was diffracted by X-rays, and end points of the {2 0 0} plane, {1 1 0} plane, and {2 1 1} plane were prepared. Obtain the crystal orientation distribution function ODF (Orientation Determination Function) of the central area from the endpoint graphs. And according to the crystal orientation distribution function, the concentration degree of {5 5 7}<7 14 5> orientation is obtained.

(The composition of silicon steel plate) In this embodiment, the composition of the silicon steel sheet contains basic elements, and optionally contains selective elements, and the remaining part is composed of Fe and impurities. In the following, the symbol "%" related to the composition of ingredients means "mass %".

In this embodiment, among the composition of silicon steel sheets, Si, Al, and Mn are basic elements (mainly alloying elements).

Si: 0.01～3.50% Si (silicon) is an element that reduces the magnetic flux density and hardens the steel sheet, resulting in a decrease in workability during the manufacture of the steel sheet and a reduction in punching workability. On the other hand, it is an element that can increase the resistance of the steel sheet and reduce eddy. The element of current loss and the effect of reducing iron loss.

If Si is greater than 3.50%, the magnetic flux density and punching workability will be significantly reduced, and the manufacturing cost will be increased, so Si is set to 3.50% or less. And it should be below 3.20%, more preferably below 3.00%. On the other hand, if Si is less than 0.01%, the electrical resistance of the steel sheet does not increase, and iron loss cannot be reduced, so Si is made 0.01% or more. It should be more than 0.10%, more than 0.50%, more than 2.00%, more than 2.10%, and more than 2.30%.

Al: 0.001~2.500% Although Al (aluminum) is inevitably mixed from ore and refractory, it contributes to deoxidation, and is an element that can play the role of increasing resistance, reducing eddy current loss and reducing iron loss, like Si.

If Al is less than 0.001%, deoxidation will not proceed sufficiently, and the electrical resistance of the steel sheet will not increase, resulting in no reduction in iron loss, so Al is set to 0.001% or more. It should be more than 0.010%, more than 0.050%, more than 0.50%, and more than 0.60%.

On the other hand, if Al exceeds 2.500%, the saturation magnetic flux density will decrease, resulting in a decrease in magnetic flux density, so Al is set to 2.500% or less. It should be below 2.000%, more preferably below 1.600%.

Mn: 0.01～3.00% Mn (manganese) is an element that increases resistance, reduces eddy current loss, and can suppress the formation of {111}<112> aggregate structure, which is less ideal for magnetic properties.

If Mn is less than 0.01%, the effect of addition cannot be sufficiently obtained, so Mn is made 0.01% or more. It should be more than 0.15%, more than 0.40%, more than 0.60%, and more than 0.70%. On the other hand, if Mn is greater than 3.00%, the grain growth during annealing will decrease and the iron loss will increase, so Mn is set to 3.00% or less. And it should be below 2.50%, more preferably below 2.00%.

In this embodiment, the silicon steel sheet contains impurities as its component composition. In addition, the so-called "impurity" refers to materials mixed from ore and scrap as raw materials, or from the manufacturing environment, etc. when steel is manufactured industrially. It refers to elements such as C, P, S, N and B. In order to fully exert the effects of the present embodiment, it is desirable to limit these impurities to the following. Moreover, it is ideal to have less content of impurities, so there is no need to limit the lower limit, and the lower limit of the impurities can also be 0%.

C: below 0.0030% C (carbon) is an element that increases iron loss, and is also an impurity element that causes magnetic aging. The less C, the better, so C is set to 0.0030% or less. It should be less than 0.0025%, more preferably less than 0.0020%. The lower limit of C is not particularly limited, but when considering industrial purification technology, 0.0001% is the lower limit in practical terms, and if considering the manufacturing cost, it is preferably 0.0005% or more.

P: below 0.180% P (phosphorus) can increase the tensile strength without reducing the magnetic flux density, but it is also an impurity element that will make the steel plate brittle. If P is greater than 0.180%, the toughness will be reduced, and the steel sheet will easily break, so P is set to 0.180% or less.

From the viewpoint of suppressing the fracture of the steel plate, the less P, the better, so it should be below 0.150%, and more preferably below 0.120%. The lower limit of P is not particularly limited, but if the industrial purification technology is considered, 0.0001% is the lower limit, and if the manufacturing cost is considered, 0.001% is the substantial lower limit.

S: 0.003% or less S (sulfur) is an impurity element that can form fine sulfides such as MnS and hinder the recrystallization and grain growth of finish annealing and the like. If S is greater than 0.003%, recrystallization and grain growth during completion annealing etc. will be significantly hindered, so S is set to 0.003% or less. As S is as small as possible, it should be less than 0.002%, more preferably 0.001% or less.

The lower limit of S is not particularly limited, but if the industrial purification technology is considered, 0.0001% is the lower limit, and if the manufacturing cost is considered, 0.0005% is the substantial lower limit.

N: below 0.003% N (nitrogen) is an impurity element that forms precipitates and causes an increase in iron loss. If N is greater than 0.003%, iron loss will increase significantly, so N is set to 0.003% or less. And it should be below 0.002%, more preferably below 0.001%. The lower limit of N is not particularly limited, but if the industrial purification technology is considered, 0.0001% is the lower limit, and if the manufacturing cost is considered, 0.0005% is the substantial lower limit.

B: below 0.002% B (boron) is an impurity element that forms precipitates and causes an increase in iron loss. If B is greater than 0.002%, iron loss will increase significantly, so B is set to 0.002% or less. And it should be below 0.001%, more preferably below 0.0005%. The lower limit of B is not particularly limited, but if the industrial purification technology is considered, 0.0001% is the lower limit, and if the manufacturing cost is considered, 0.0005% is the substantial lower limit.

In this embodiment, the silicon steel sheet may contain selective elements in addition to the basic elements and impurities described above. For example, Sb, Sn, Cu, REM, Ca, and Mg may also be included as selective elements to replace a part of the remaining Fe. As long as the selection elements are included depending on the purpose. Therefore, there is no need to limit the lower limit of these selected elements, and the lower limit can also be 0%. In addition, even if these selective elements are contained as impurities, the above effects will not be impaired.

Sb: 0～0.05% Sb (antimony) is an element that can suppress the nitridation of the surface of the steel sheet and help reduce iron loss. If Sb is greater than 0.05%, the toughness of steel will be reduced, so Sb is set to 0.05% or less. And it should be below 0.03%, more preferably below 0.01%. The lower limit of Sb is not particularly limited, and may be 0%. In order to suitably obtain the above effect, Sb may be 0.001% or more.

Sn: 0～0.20% Sn (tin) is an element that can suppress the nitridation of the surface of the steel sheet and help reduce iron loss. If Sn is greater than 0.20%, the toughness of the steel will be reduced, or the insulating coating will be easily peeled off, so Sn is made 0.20% or less. It should be below 0.15%, more preferably below 0.10%. The lower limit of Sn is not particularly limited, and may be 0%. In order to suitably obtain the above effect, Sn may be 0.01% or more. And it should be above 0.04%, more preferably above 0.08%.

Cu: 0~1.00% Cu (copper) is an element that can suppress the formation of {111}<112> aggregate structure, which is not ideal for magnetic properties, and can suppress the oxidation of the surface of the steel plate and make the grain growth and grain size . If Cu is greater than 1.00%, the effect of addition will be saturated, and the grain growth during finish annealing will be suppressed, and the workability of the steel sheet will be reduced, and it will be brittle during cold rolling, so Cu is set to 1.00% or less. It should be below 0.60%, more preferably below 0.40%. The lower limit of Cu is not particularly limited, and may be 0%. In order to appropriately obtain the above-mentioned effects, Cu may be 0.10% or more. And it should be more than 0.20%, more preferably more than 0.30%.

REM: 0~0.0400% Ca: 0~0.0400% Mg: 0~0.0400% REM (Rare Earth Metal), Ca (calcium), and Mg (magnesium) systems can be used to fix S as a sulfide or oxysulfide to suppress fine precipitation of MnS, etc., and promote recrystallization and grain growth during finish annealing Element of the role.

If REM, Ca and Mg are greater than 0.0400%, sulfide or oxysulfide will be excessively generated, which will hinder the recrystallization and grain growth during finish annealing, so REM, Ca and Mg are all set to 0.0400% or less. Preferably, all elements are below 0.0300%, more preferably below 0.0200%.

The lower limit of REM, Ca, and Mg is not particularly limited, and may be 0%. In order to suitably obtain the above-mentioned effects, all of REM, Ca, and Mg should be 0.0005% or more. Preferably, all elements are above 0.0010%, more preferably above 0.0050%.

Here, REM refers to a total of 17 elements of Sc, Y, and lanthanides, and at least one of them. The above REM content refers to the total content of at least one of these elements. If it is a lanthanide element, it is added industrially in the form of a rare earth metal alloy.

In this embodiment, the composition of the silicon steel sheet preferably contains at least one of the following elements: in mass%, Sb: 0.001 to 0.05%, Sn: 0.01 to 0.20%, Cu: 0.10 to 1.00%, REM: 0.0005 to 0.0400 %, Ca: 0.0005~0.0400% or Mg: 0.0005~0.0400%.

The above-mentioned steel composition can be measured by the general analysis method of steel. For example, the steel composition may be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). In addition, C and S may be measured using a combustion-infrared absorption method, N using an inert gas fusion-thermal conductivity method, and O using an inert gas fusion-non-dispersive infrared absorption method.

In addition, the above-mentioned component composition is the component composition of a silicon steel sheet, and when the silicon steel sheet which becomes a measurement sample has an insulating film etc. on the surface, it is the component composition measured after removing it.

As a method of removing the insulating coating of the non-oriented electromagnetic steel sheet, for example, there is a non-oriented electromagnetic steel sheet having an insulating coating, etc., sequentially immersed in an aqueous solution of sodium hydroxide, an aqueous solution of sulfuric acid, and an aqueous solution of nitric acid, washed, and then Warm air drying method. Through this series of processing, the silicon steel sheet with the insulating coating removed can be obtained.

(Magnetic characteristics of electromagnetic steel sheet) As a split iron core, the non-oriented electromagnetic steel sheet of this embodiment should preferably be excellent in both the rolling direction and the sheet width direction (direction perpendicular to the rolling direction) Magnetic properties. Therefore, the average of the magnetic flux density in the rolling direction and the magnetic flux density in the plate width direction when excited with a magnetizing force of 5000 A/m is the magnetic flux density B ₅₀ , and the saturated magnetic flux density in the rolling direction and the plate width The average saturation magnetic flux density in the direction is the saturation magnetic flux density Bs. In this case, the ratio B ₅₀ /Bs of the magnetic flux density B ₅₀ to the saturation magnetic flux density Bs is preferably 0.82 or more.

The above B ₅₀ /Bs is preferably 0.84 or more, more preferably 0.86 or more, and even more preferably 0.90 or more. On the other hand, the saturation magnetic flux density Bs is the maximum magnetic flux density obtained when the maximum magnetic field is loaded, so the maximum value of B ₅₀ /Bs is 1. The upper limit of B ₅₀ /Bs is not particularly limited, as long as it is 1.00. And it should be below 0.98.

The {5 5 7}<7 14 5> azimuth controlled in this embodiment is the azimuth close to the {4 1 1}<1 4 8> azimuth, and the {4 1 1}<1 4 8> azimuth is close to Improve the azimuth of {1 0 0}<0 1 2> azimuth of the magnetic flux density B _{50 in} the rolling direction and the sheet width direction. Therefore, in this embodiment, the magnetic properties can be improved in both the rolling direction and the sheet width direction.

The magnetic properties of the electromagnetic steel sheet can be measured, for example, with Single Sheet Tester (SST), in units of T (Tesla), when the magnetizing force is 5000 A/m, the relative magnetic flux density in the rolling direction and the sheet width direction when the steel sheet is magnetized Calculate the magnetic flux density B ₅₀ , and in the same way, measure the relative magnetic flux density in the rolling direction and the sheet width direction when the steel plate is loaded with the maximum magnetic field in the unit of T (Tesla), and obtain the saturated magnetic flux density Bs .

(Punching workability of electromagnetic steel plate) Since the non-oriented electrical steel sheet of this embodiment improves the degree of {5 5 7}<7 14 5> azimuth concentration, the machining accuracy during punching will be improved. For example, when circular punching is performed, the roundness of the processed product becomes smaller.

In addition, the roundness can be evaluated by the difference between the maximum radius and the minimum radius of the circular punched product. For example, when a round product with a radius of 200 mm is punched, the maximum radius and minimum radius of the punched product are measured, and the difference may be obtained.

In this embodiment, the roundness is preferably 45 μm or less, and more preferably 40 μm or less. On the other hand, the lower limit of roundness is not particularly limited. However, since it is practically difficult to control the roundness to less than 5 μm, the lower limit may be set to 5 μm.

As described above, in the present embodiment, the degree of aggregation in the {5 5 7}<7 14 5> azimuth in the central region in the plate thickness direction is higher than that of a general steel plate, so the punching workability is improved. The mechanism for improving the punching workability is speculated as follows.

The {5 5 7}<7 14 5> azimuth controlled in this embodiment is the azimuth close to the {111}<112> azimuth. In this {111} direction, the hardness anisotropy in the entire circumferential direction is small, so the area where the steel sheet is stretched and deformed during punching is approximately equal in the entire circumferential direction. Therefore, it is considered that if the degree of accumulation of {5 5 7}<7 14 5> orientation increases, the punching workability will also increase.

(As other characteristics of electromagnetic steel plate) The thickness of the silicon steel plate is not particularly limited as long as it is appropriately adjusted according to its use. However, from the manufacturing point of view, the thickness of the silicon steel plate should be above 0.10mm, and more preferably above 0.15mm. On the other hand, the thickness of the silicon steel plate should be below 0.50mm, more preferably below 0.35mm.

The non-oriented electromagnetic steel sheet of this embodiment may have an insulating coating on the surface of the silicon steel sheet. The type of the insulating coating is not particularly limited, as long as it is appropriately selected from known insulating coatings depending on its use.

For example, the insulating film may be an organic film or an inorganic film. Examples of organic coatings include polyamine resins, acrylic resins, acrylic-styrene resins, alkyd resins, polyester resins, polysiloxane resins, fluorine resins, polyolefin resins, styrene resins, vinyl acetate resins, Coatings of epoxy resin, phenol resin, urethane resin, melamine resin, etc.

Examples of inorganic coatings include phosphate coatings and aluminum phosphate coatings. In addition, an organic-inorganic composite film containing the above-mentioned resin can also be mentioned. The film thickness of the insulating film is not particularly limited, but the film thickness per side is preferably 0.05 to 2 μm.

Next, a method of manufacturing the non-oriented electrical steel sheet of this embodiment will be described.

FIG. 2 is a flowchart illustrating a method of manufacturing a non-oriented electrical steel sheet according to this embodiment. In this embodiment, the molten steel with the adjusted composition is cast, hot rolled, and then subjected to heat treatment, pickling, and cold rolling during cooling after hot rolling, followed by finishing annealing to produce silicon Steel plate. Furthermore, an insulating coating is further provided on the silicon steel sheet to produce a non-oriented electromagnetic steel sheet.

In this embodiment, each step is controlled to control the ratio of the recrystallized structure to the non-recrystallized structure (non-recrystallized fraction) in the steel sheet before cold rolling and rolling, and also to control the cold rolling and finishing annealing. Increase the concentration of {5 5 7}<7 14 5> orientation of the central area of the silicon steel plate in the thickness direction.

The unrecrystallized fraction before cold rolling is not controlled by a single condition such as the steel composition, the temperature of hot rolling delay, the shrinkage rate of hot rolling delay, and the cooling conditions after hot rolling delay. The technical characteristics of the technology, but the technical characteristics of the various steps and conditions can affect each other in a complex way to control.

in particular, The Si content of the steel composition is a factor that affects the fact that the constituent phase of the steel structure becomes the α phase and/or the γ phase due to the hot rolling temperature. The Si content becomes higher in the range of 0.01 to 3.50%, then The non-recrystallization fraction before cold rolling is larger. The Al content of the steel composition is a factor that affects the fact that the constituent phase of the steel structure becomes the α phase and/or the γ phase due to the hot rolling temperature. The higher the Al content in the range of 0.001 to 2.500%, then The non-recrystallization fraction before cold rolling is larger. The Mn content of the steel composition is a factor that affects the amount of MnS produced, and the amount of MnS produced will affect the driving force for recrystallization. The Mn content becomes higher in the range of 0.01 to 3.00%, and the The greater the recrystallization fraction. The temperature of the hot rolling delay, specifically the heating temperature of the steel blank before hot rolling, is a factor that affects the composition phase of the steel structure to become the α phase and/or the γ phase, and it will affect the hot rolling process. The factor of the formation of the structure, the higher the heating temperature of the steel blank before hot rolling is in the range of 1000~1300 ℃, the greater the non-recrystallization fraction before cold rolling. The temperature of the hot rolling delay, specifically the final rolling temperature at the completion of hot rolling, is a factor that affects the constituent phase of the steel structure to become the α phase and/or the γ phase, and it will affect the hot rolling process. The factor for the formation of the structure, the higher the final rolling temperature at the completion of hot rolling in the range of 800 to 950°C, the lower the non-recrystallization fraction before cold rolling. The reduction ratio of hot rolling delay is a factor that affects the formation of hot rolling processing structure. The cumulative reduction ratio of hot rolling delay becomes larger in the range of 98~99.5%, the unrecrystallized fraction before cold rolling delay The lower the rate. The cooling conditions after hot rolling, specifically the cooling rate from the end of the hot rolling to the holding temperature, is a factor that affects the recovery and recrystallization of the hot rolling process structure. The average cooling in this temperature range The faster the speed becomes in the range of 80 to 200°C/sec, the greater the fraction of unrecrystallized before cold rolling. The cooling conditions after hot rolling, specifically, the holding temperature during the holding process, are also factors that affect the recovery and recrystallization of the hot rolling processing structure. The holding temperature during the holding process varies from 700 to 850°C. The higher the value, the smaller the unrecrystallized fraction before cold rolling. The cooling conditions after hot rolling delay, specifically the holding time during heat preservation treatment, are also factors that will affect the recovery and recrystallization of the hot rolling processing structure. The holding time during heat preservation treatment varies from 10 to 180 minutes The longer it is, the smaller the unrecrystallized fraction before cold rolling is extended.

In this embodiment, the above conditions are deliberately, compositely and inseparably controlled to carefully prepare the steel structure so that the unrecrystallized fraction before cold rolling is 1/10 or more and 1/1 in the structure 5 or less, even if the area fraction is 10-20%.

Next, the steel sheet whose unrecrystallized fraction before cold rolling is controlled is subjected to cold rolling and finish annealing, and controlled so that {5 5 7}<7 14 5> azimuth grains will preferentially recrystallize.

{5 5 7}<7 14 5> The degree of azimuth concentration is not a single step, such as the unrecrystallized fraction before cold rolling, the shrinkage rate of cold rolling, and the heating rate during finish annealing. The technical characteristics that can be controlled by a single condition, and the technical characteristics that can be controlled by the conditions of each step compounding and interacting with each other.

in particular, The shrinkage rate of cold rolling delay is a factor that affects the formation of cold rolling processing structure, and the cold rolling processing structure will become the base of {5 5 7}<7 14 5> azimuthal grain recrystallization, the accumulation of cold rolling delay The greater the shrinkage ratio in the range of 80 to 95%, the smaller the degree of {5 5 7}<7 14 5> azimuth concentration. The heating rate at the completion of annealing, specifically, the heating rate from the starting temperature to 750°C, is a factor that affects the recrystallization nucleation of {5 5 7}<7 14 5> azimuth grains, The closer the average heating rate in this temperature range is to the central value in the range of 5-50°C/sec, the greater the degree of {5 5 7}<7 14 5> azimuth concentration. The rate of temperature rise during finish annealing, specifically the rate of temperature rise from 750°C to the soaking temperature of finish annealing, will affect the grain growth of {5 5 7}<7 14 5> azimuthal grains Factor, the faster the average heating rate in this temperature range becomes in the range of 20 to 100°C/sec, the greater the degree of {5 5 7}<7 14 5> azimuth concentration.

In this embodiment, the above conditions are deliberately, compositely, and inseparably controlled to carefully fabricate the steel structure so that the center area of the silicon steel sheet in the thickness direction {5 5 7}<7 14 5> The degree of aggregation is 12 or more and 35 or less.

As mentioned above, the degree of {5 5 7}<7 14 5> azimuth concentration is not a technical feature that can be obtained by a single condition with only one step of the control sheet. {5 5 7}<7 14 5> The degree of azimuth concentration is a technical feature that can be produced by controlling the conditions of cold rolling and finishing annealing in addition to controlling the non-recrystallization fraction before cold rolling. .

Specifically, the manufacturing method of the non-oriented electrical steel sheet of this embodiment includes: a casting step, a hot rolling step, a heat preservation treatment step, a pickling step, a cold rolling step, a finish annealing step, and a film forming step; The steel embryo is cast in the casting step. The composition of the steel embryo contains: in mass%, Si: 0.01~3.50%, Al: 0.001~2.500%, Mn: 0.01~3.00%, C: 0.0030% or less, P: 0.180% or less, S: 0.003% or less, N: 0.003% or less, B: 0.002% or less, Sb: 0~0.05%, Sn: 0~0.20%, Cu: 0~1.00%, REM: 0~0.0400%, Ca: 0~0.0400% and Mg: 0~0.0400%, and the rest is composed of Fe and impurities; In the hot rolling step, the heating temperature of the steel blank before hot rolling is set to 1000 to 1300°C, the final rolling temperature at the completion of hot rolling is set to 800 to 950°C, and the cumulative reduction rate of hot rolling delay is set to 98~99.5%, the average cooling rate from the end of hot rolling to the holding temperature of the holding process is set to 80~200℃/sec; In the heat preservation treatment step, the heat preservation temperature is set to 700~850°C, and the heat preservation time is set to 10~180 minutes, and The unrecrystallized fraction of the steel sheet before the cold rolling step is controlled at 10-20 area%; In the cold rolling extension step, the cumulative reduction rate of the cold rolling delay is set to 80 to 95%; In the finishing annealing step, the average heating rate from the starting temperature to 750°C is set to 5 to 50°C/sec, and the average heating rate from 750°C to the soaking temperature for finishing annealing is 20 to 100 Within the range of ℃/sec, the temperature is changed to a faster temperature increase rate than the above average temperature increase rate to 750° C., and the soaking temperature of the finish annealing is set to be higher than the recrystallization temperature.

Hereinafter, a preferred manufacturing method will be described in order from the casting step.

(Casting step) In the casting step, the steel with the above composition is melted in a converter, electric furnace, or the like, and the molten steel is used to manufacture a steel blank. Continuous casting can be used to manufacture steel blanks, or after molten steel is used to produce ingots, the ingots are rolled in blocks to produce steel blanks. In addition, other methods can also be used to manufacture steel blanks. The thickness of the steel blank is not particularly limited, and may be, for example, 150 to 350 mm. The thickness of the steel embryo is preferably 220~280mm. As the steel embryo, a so-called thin steel embryo with a thickness of 10 to 70 mm can also be used.

In the casting step, the Si content of the steel composition is controlled in the range of 0.01 to 3.50%, the Al content is controlled in the range of 0.001 to 2.500%, and the Mn content is controlled in the range of 0.01 to 3.00%, so that the cold rolling is extended The unrecrystallized fraction of the former steel plate is 10-20 area%.

The Si content should be more than 0.10%, more than 0.50%, more than 2.00%, more than 2.10%, more than 2.30%. Moreover, the Si content is preferably 3.20% or less, and more preferably 3.00% or less. The Al content should be above 0.010%, more preferably above 0.050%, more preferably above 0.50%, and more preferably above 0.60%. Also, the Al content is preferably below 2.000%, and more preferably below 1.600%. The Mn content should be above 0.15%, more preferably above 0.40%, more preferably above 0.60%, and more preferably above 0.70%. Also, the Mn content is preferably 2.50% or less, and more preferably 2.00% or less.

(Hot rolling step) In the hot rolling step, the steel blank may be hot rolled using a hot rolling machine. The hot rolling mill includes, for example, a rough rolling mill and a finishing rolling mill disposed downstream of the rough rolling mill. After the heated steel is rolled with a rough rolling machine, it is further rolled with a finishing rolling machine to produce a hot-rolled steel sheet.

In the hot rolling step, the heating temperature of the steel blank before hot rolling is controlled within the range of 1000~1300℃, and the final rolling temperature during the completion of hot rolling is controlled within the range of 800~950℃. The cumulative shrinkage rate is controlled within the range of 98~99.5%, and the average cooling rate from the end temperature of the hot rolling to the temperature of the heat preservation treatment is controlled within the range of 80~200℃/sec. The non-recrystallized fraction of the steel plate is 10-20 area%.

The heating temperature of the steel embryo is preferably above 1100°C, more preferably above 1150°C. Moreover, the heating temperature of the steel embryo is preferably below 1250°C, more preferably below 1200°C. The final rolling temperature should be above 850℃. Also, the final rolling temperature is preferably 900°C or lower. The average cooling rate is preferably 100°C/sec or more, and more preferably 120°C/sec or more. Moreover, the average cooling rate is preferably 180°C/sec or less, and more preferably 150°C/sec or less.

In addition, the thickness of the steel plate should be 20~100mm at the beginning of the completion of hot rolling. In addition, the cumulative reduction ratio of hot rolling is defined as follows. Cumulative rolling reduction rate (%) = (1-plate thickness after hot rolling/plate thickness before hot rolling)×100

(Insulation treatment steps) In the heat preservation treatment step, the hot-rolled steel sheet is kept warm during the cooling process after the hot-rolling is delayed. In the heat preservation treatment step, the heat preservation temperature is controlled in the range of 700~850℃, and the heat preservation time is controlled in the range of 10~180 minutes, so that the unrecrystallized fraction of the steel sheet before cold rolling is 10~20 area%.

The holding temperature should be above 750℃, more preferably above 780℃. In addition, the holding temperature is preferably below 830°C, more preferably below 800°C. The holding time should be more than 20 minutes, more preferably more than 30 minutes, and more preferably more than 40 minutes. Also, the holding time should be less than 150 minutes, more preferably less than 120 minutes, and more preferably less than 100 minutes.

(Pickling step) In the pickling step, pickling is performed to remove rust generated on the surface of the hot-rolled steel sheet. The pickling conditions during pickling of the hot-rolled sheet are not particularly limited, and may be performed under well-known conditions.

(Steel plate before cold rolling step) In this embodiment, the steel sheet that has undergone the above casting step, hot rolling step, heat preservation treatment step, and pickling step and that is before the cold rolling step is controlled to have a non-recrystallized fraction in the structure of 10 ~20 area%.

One of the main orientations of conventional non-oriented electrical steel sheets is the {1 1 1}<1 1 2> orientation. In general, the grains in this orientation are formed by recrystallizing the steel sheet structure before cold rolling, introducing strain into the structure by cold rolling, and recrystallizing from the crystal grain boundaries at the completion of annealing Core and grow. On the other hand, in this embodiment, only a predetermined amount of unrecrystallized structure remains in the steel sheet structure before cold rolling, and the cold rolling conditions and finish annealing conditions are appropriately controlled to form deliberately {5 5 7} <7 14 5> azimuth grains.

In addition, if the above-mentioned non-recrystallization fraction does not satisfy 10 to 20 area%, it will eventually become impossible to control the degree of {5 5 7}<7 14 5> orientation aggregation. In addition, if the steel sheet structure before cold rolling contains a non-recrystallized structure larger than a predetermined amount, it is difficult to form {4 1 1}<1 4 8> that can effectively improve the magnetic properties in the structure after completion of annealing Azimuthal grains. Therefore, in order to take into account both excellent magnetic properties and punching workability, it is most suitable to control the unrecrystallized fraction of the steel sheet before the cold rolling step to 10-20 area%.

In the prior art, after the hot-rolling step, the hot-rolled steel sheet is cooled to near room temperature, then heated again, and the hot-rolled sheet is annealed at a soaking temperature of 800 to 1050°C and a soaking time of less than 1 minute. However, with this hot-rolled sheet annealing, it is difficult to stably produce a recrystallized structure and a non-recrystallized structure at the above ratio in the steel sheet structure before cold rolling.

In this embodiment, in order to control the non-recrystallization fraction of the steel sheet before cold rolling, the above-mentioned heat preservation treatment is performed on the steel sheet during cooling after hot rolling. In addition, after the steel plate after the heat preservation is cooled to near room temperature, the hot rolled plate annealing is not performed. Results Because the non-recrystallized fraction of the steel sheet before cold rolling was suitably controlled, the concentration of {5 5 7}<7 14 5> azimuth concentration in the center area of the steel sheet in the thickness direction could be finally improved.

In addition, the unrecrystallized fraction of the steel sheet before the cold rolling step can be measured by the following method. The surface of the test piece of about 25 mm × 25 mm cut from the steel sheet before the cold rolling step is mechanically ground to reduce the thickness to 1/2 of the thickness of the steel sheet. The polishing surface was subjected to chemical polishing or electrolytic polishing to remove strain, and a test piece for measurement was prepared.

For the test piece for measurement, EBSD (Electron Back Scattering Diffraction) is performed, and the non-recrystallization fraction in the observation field may be calculated from the KAM (Kernel Average Misorientation) value. In addition, for example, crystal grains having a KAM value of 2.0 or more in the observation field can be determined as non-recrystallized crystal grains. As long as the observation field of view is changed and EBSD measurement is performed at 10 or more points, the total area of the observation field may be 1,000,000 μm ² or more.

As described above, in this embodiment, it is preferable not to perform hot-rolled sheet annealing during the period from the hot rolling step to the cold rolling step. That is, in this embodiment, the hot rolling step, the heat preservation treatment step, the pickling step, and the cold rolling step are preferably continuous steps. Specifically, it is preferable to apply heat preservation treatment to the steel sheet after the hot rolling step, to perform pickling to the steel sheet after the heat preservation treatment step, and to perform cold rolling to the steel sheet after the pickling step.

(Cold rolling step) In the cold rolling step, cold rolling is performed on the steel sheet whose unrecrystallized fraction is controlled to 10 to 20 area%. In the cold rolling extension step, the cumulative rolling reduction of the cold rolling delay is controlled in the range of 80 to 95%, so that the {5 5 7}<7 14 5> azimuth concentration degree after finishing annealing is 12 to 35. The cumulative shrinkage ratio should be more than 83%, more preferably more than 85%.

In addition, the cumulative reduction rate of cold rolling is defined as follows. Cumulative shrinkage ratio (%) = (1-plate thickness after cold rolling/plate thickness before cold rolling)×100

(Complete annealing step) In the finish annealing step, finish annealing is performed on the cold-rolled steel sheet. In the finishing annealing step, the average heating rate in the temperature range from the starting temperature to 750°C is controlled within the range of 5 to 50°C/sec, from 750°C to the soaking temperature of the finishing annealing The average heating rate in the temperature range is in the range of 20 to 100°C/sec. It is controlled to be faster than the above average heating rate up to 750°C, and the soaking temperature of the finish annealing is controlled to the recrystallization temperature As described above, the degree of azimuth concentration after {5 5 7}<7 14 5> after finishing annealing is 12~35.

The average heating rate up to 750°C is preferably 10°C/sec or more, and more preferably 20°C/sec or more. In addition, the average heating rate up to 750°C is preferably 40°C/sec or less, and more preferably 30°C/sec or less. The average heating rate from 750°C is preferably 30°C/sec or more, and more preferably 40°C/sec or more. In addition, the average heating rate from 750°C is preferably 80°C/sec or less, and more preferably 60°C/sec or less.

The soaking temperature during annealing is preferably 800~1200℃. And the soaking temperature should be above 850℃. The soaking time should be 5~120 seconds. And the soaking time should be more than 10 seconds, more preferably more than 20 seconds.

After the above-mentioned finish annealing, the concentration of {5 5 7}<7 14 5> orientation in the central area of the steel plate (silicon steel plate) in the thickness direction is controlled at 12 to 35.

(Coating process) In the film forming step, an insulating film is formed on the silicon steel sheet after the finish annealing. The insulating coating may be, for example, an organic coating or an inorganic coating. In addition, as the forming conditions of the insulating film, the same forming conditions as the insulating film of the conventional non-oriented electrical steel sheet can also be used.

The non-directional electromagnetic steel plate with proper control of {5 5 7}<7 14 5> azimuth concentration by the above steps can be suitable as magnetic material for rotating machines, small and medium-sized transformers and electronic components, and is particularly suitable as Magnetic material for split core of motor.

Hereinafter, a case where the non-oriented electrical steel sheet of the present embodiment is applied as a divided core of a motor will be described.

FIG. 3 shows an aspect of the divided iron core of the motor. As shown in FIG. 3, the motor core 100 is composed of a punching member 11 and a layered body 13 which is formed by integrating the punching member 11. The punching member 11 is made by punching a non-oriented electromagnetic steel sheet. The punching member 11 includes a yoke portion 17 on a circular arc and a tooth portion 15 protruding radially inward from the inner peripheral surface of the yoke portion 17. By connecting the punching member 11 into an annular shape, the motor core 100 can be constructed.

In addition, the shape of the punching member 11, the number connected in a ring shape, the number of layers, etc., can be designed depending on the purpose.

Examples Next, the effects of one aspect of the present invention will be described in more detail in detail using examples, but the conditions in the examples are examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited For this condition example. As long as the purpose of the present invention can be achieved without departing from the gist of the present invention, the present invention can adopt various conditions.

<Example 1> After casting the steel blank with the adjusted composition, the manufacturing conditions in each step are controlled to produce a silicon steel plate. Table 1 and Table 2 show the chemical composition of the silicon steel sheet, and Table 3 to Table 8 show the manufacturing conditions. In addition, at the time of the above production, hot rolling and heat preservation treatment were performed under the conditions shown in Tables 3 to 5, and after pickling after cooling to room temperature. In addition, the sample described as "Hot rolled sheet annealing" in the "Heat preservation treatment step" column in the table is cooled to room temperature without heat preservation during cooling after hot rolling, and then in a 100% nitrogen gas In the environment, the hot-rolled sheet was annealed at 800°C for 60 seconds, and then pickled after cooling to room temperature.

For the steel sheet that has gone through the casting step, hot rolling step, heat preservation treatment step and pickling step and is the steel plate before the cold rolling step, the unrecrystallized fraction in the structure is measured, and the obtained results are shown in Table 3 to Table 5. In addition, the non-recrystallization fraction was measured according to the above method.

The steel sheet after the determination of the non-recrystallization fraction was subjected to cold rolling and finish annealing under the conditions shown in Table 6 to Table 8. In the finish annealing, the soaking temperature is set to 800 to 1100°C or more, which is the recrystallization temperature, and the soaking time is set to 30 seconds. In addition, a phosphoric acid-based insulating film having an average thickness of 1 μm is formed on the silicon steel sheet after the finish annealing. In addition, with regard to the "Complete Annealing Step" column in the table, "heating rate A" indicates the average heating rate from the starting temperature to 750°C, and "heating rate B" indicates the soaking from 750°C to finish annealing The average heating rate up to temperature, and "heating rate control" indicates the relationship between the heating rate A and the heating rate B.

For the produced non-directional electromagnetic steel sheet, the concentration of {5 5 7}<7 14 5> orientation of the central area of the silicon steel sheet in the thickness direction is measured and the result is shown in the "Aggregation Aggregation Degree" in Table 6~Table 8. In addition, the degree of {5 5 7}<7 14 5> azimuth concentration was measured according to the method described above.

Table 1 and Table 2 show the chemical composition of the silicon steel sheet, and Table 3 to Table 8 show the manufacturing conditions and manufacturing results. Moreover, the chemical composition of the steel embryo and the chemical composition of the silicon steel plate are substantially the same. In the table, the symbol "-" of the chemical composition of the silicon steel sheet indicates that no alloying elements were intentionally added, or the content was below the detection detection limit. In the table, the value with a bottom line indicates that it is outside the scope of the present invention.

Using the produced non-oriented electrical steel sheet, the magnetic flux density as a magnetic characteristic and the roundness of a round punched product as a punching workability were evaluated. The magnetic flux density and roundness are evaluated according to the above method. When B ₅₀ /Bs is 0.82 or more, it is determined that the magnetic characteristics are good. In addition, when the roundness of the circular punched product is 45 μm or less, it is judged that the punching workability is good.

The evaluation results of magnetic properties and punching workability are shown in Table 6 to Table 8. The examples of the present invention of Test Nos. B1 to B22 have suitably controlled the composition and aggregate structure of the silicon steel sheet, so the non-oriented electrical steel sheet has excellent magnetic properties and punching workability.

On the other hand, in the comparative examples of Test Nos. b1 to b44, since the silicon steel sheet is not suitable for controlling at least one of the component composition or assembly structure, either the magnetic properties of the non-oriented electrical steel sheet or the punching workability Unsatisfied.

FIG. 4 shows the relationship between the degree of {5 5 7}<7 14 5> azimuth and roundness. This FIG. 4 is a graph showing the relationship between the degree of {5 5 7}<7 14 5> azimuth concentration and roundness according to Examples B1 to B22 and Comparative Examples b1 to b44 of the present invention. Figure 4 shows that as the {5 5 7}<7 14 5> azimuth gathers, the value of true roundness becomes smaller.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

[Table 8]

Industrial availability According to the above aspect of the present invention, in addition to punching workability, it is possible to provide a non-oriented electrical steel sheet excellent in magnetic properties in both the rolling direction and the sheet width direction in addition to punching workability and a method for manufacturing the same . Therefore, the industrial availability is high.

1‧‧‧non-oriented electromagnetic steel plate 3‧‧‧Silicon steel plate (base material steel plate) 5‧‧‧Insulation film (tension film) 11‧‧‧Punching components 13‧‧‧Layered body 15‧‧‧tooth 17‧‧‧Yoke 100‧‧‧Motor core

1 is a schematic cross-sectional view showing a non-oriented electrical steel sheet according to an embodiment of the present invention. FIG. 2 is a flowchart showing the method of manufacturing the non-oriented electrical steel sheet according to this embodiment. FIG. 3 is a schematic diagram showing one aspect of the motor iron core. FIG. 4 is a diagram showing the relationship between the degree of {5 5 7}<7 14 5> azimuth concentration and roundness.

Claims (4)

A non-directional electromagnetic steel plate with silicon steel plate and insulating coating; The characteristics of the non-oriented electromagnetic steel plate are: The composition of the aforementioned silicon steel sheet contains: In terms of mass %, Si: 0.01~3.50%, Al: 0.001~2.500%, Mn: 0.01~3.00%, C: 0.0030% or less, P: below 0.180%, S: 0.003% or less, N: 0.003% or less, B: 0.002% or less, Sb: 0~0.05%, Sn: 0~0.20%, Cu: 0~1.00%, REM: 0~0.0400%, Ca: 0~0.0400% and Mg: 0~0.0400%, and The remainder consists of Fe and impurities; and The {5 5 7}<7 14 5> azimuth concentration in the central area of the silicon steel sheet in the thickness direction is 12 or more and 35 or less. The non-oriented electrical steel sheet according to claim 1, wherein the aforementioned composition of the aforementioned silicon steel sheet contains at least one of the following elements: In terms of mass %, Sb: 0.001~0.05%, Sn: 0.01~0.20%, Cu: 0.10~1.00%, REM: 0.0005~0.0400%, Ca: 0.0005~0.0400% and Mg: 0.0005~0.0400%. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the aforementioned concentration degree of {5 5 7}<7 14 5> orientation is 18 or more and 35 or less. A method for manufacturing a non-oriented electrical steel sheet is to manufacture a non-oriented electrical steel sheet according to any one of claims 1 to 3, the method is characterized by: With casting step, hot rolling step, heat preservation treatment step, pickling step, cold rolling step, finish annealing step and film forming step; Casting a steel embryo in the aforementioned casting step, the composition of the steel embryo contains: In terms of mass %, Si: 0.01~3.50%, Al: 0.001~2.500%, Mn: 0.01~3.00%, C: 0.0030% or less, P: below 0.180%, S: 0.003% or less, N: 0.003% or less, B: 0.002% or less, Sb: 0~0.05%, Sn: 0~0.20%, Cu: 0~1.00%, REM: 0~0.0400%, Ca: 0~0.0400% and Mg: 0~0.0400%, and The remaining part is composed of Fe and impurities; In the aforementioned hot rolling step, the heating temperature of the steel blank before hot rolling is set to 1000 to 1300°C, the final rolling temperature at the completion of hot rolling is set to 800 to 950°C, and the cumulative reduction rate of the hot rolling delay is set 98 to 99.5%, the average cooling rate from the end of the hot rolling to the holding temperature of the holding process is set to 80 to 200℃/sec; In the aforementioned heat preservation treatment step, the heat preservation temperature is set to 700 to 850°C, and the heat preservation time is set to 10 to 180 minutes, and The unrecrystallized fraction of the steel sheet before the cold rolling step is controlled to 10-20 area%; In the aforementioned cold rolling step, the cumulative rolling reduction rate of the cold rolling delay is set to 80 to 95%; In the aforementioned finish annealing step, the average heating rate from the starting temperature to 750°C is set to 5-50°C/sec, and the average heating rate from 750°C to the soaking temperature of the finish annealing is 20~ Within the range of 100°C/sec, the temperature was changed to a faster temperature rise rate than the aforementioned average temperature rise rate up to 750°C, and the soaking temperature of the finish annealing was set to be equal to or higher than the recrystallization temperature.

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