JP2019052360A - Non-oriented electrical steel sheet and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-oriented electrical steel sheet having excellent magnetic characteristics and a small anisotropy of magnetic flux density and a method for manufacturing the same. SOLUTION: The non-directional electromagnetic steel plate according to the present invention has Si: 0.1 to 3.8%, Mn: 0.1 to 2.5%, Al: 0 to 2.5%, C in mass%. : 0 to 0.003%, P: 0 to 0.25%, S: 0 to 0.003%, and N: 0 to 0.003%, Ti: 0 to 0.004%, Nb: 0 to 0 It contains 0.003%, As: 0 to 0.003%, and Zr: 0 to 0.003%, and the balance has a chemical composition consisting of Fe and impurities. The magnetic flux density B50 (LC) is 1.700T or more. The anisotropy index B50 (anisotropic) defined by the formula (1) described in the embodiment is less than 0.020. [Selection diagram] Fig. 1

Description

  The present invention relates to a non-oriented electrical steel sheet and a method for producing the same.

  Non-oriented electrical steel sheets are used as materials for iron cores of electrical equipment. Electrical equipment includes, for example, air conditioner compressors, various motors used in home appliances, and automobile drive motors.

  In the above-described electrical equipment, high energy efficiency is required. Therefore, non-oriented electrical steel sheets used for electrical equipment are required to have excellent magnetic properties, that is, low iron loss and high magnetic flux density.

  JP-A-9-217117 (Patent Document 1), JP-A-11-050151 (Patent Document 2), JP-A No. 2001-098325 (Patent Document 3), JP-A No. Hei 4- No. 124219 (Patent Document 4), Japanese Patent Laid-Open No. 2005-281853 (Patent Document 5), and Japanese Patent Laid-Open No. 2015-78412 (Patent Document 6).

  Patent Documents 1 to 4 perform special finish hot rolling in order to enhance magnetic properties in the production of electromagnetic steel sheets.

  In the method for producing a non-oriented electrical steel sheet disclosed in Patent Document 1, 1.0% <Si ≦ 4.0%, 0.10% ≦ Mn ≦ 1.0%, C ≦% by weight in the steel. A slab containing 0.0050%, N ≦ 0.0050%, S ≦ 0.0050%, the balance being Fe and inevitable impurities is roughly rolled. After rough rolling, during hot rolling finish rolling, hot rolling is performed with an average friction coefficient of the hot rolling roll and the steel sheet being 0.25 or less to obtain a hot rolled sheet. Next, after the cold rolling, finish annealing is performed. Thus, Patent Document 1 describes that the magnetic flux density is increased and the iron loss is reduced.

In the method for producing a non-oriented electrical steel sheet disclosed in Patent Document 2, 0.010% ≦ C ≦ 0.14%, 0.010% ≦ acid-soluble Al ≦ 0.050%, 0.0030 by weight%. A slab containing% ≦ N ≦ 0.0150% and comprising the balance Fe and inevitable impurities is heated and hot rolled. After hot rolling, cold rolling is performed once or more to obtain a final thickness. After decarburization annealing, final annealing is performed in a temperature range below the Ac ₁ transformation point. At the time of finish hot rolling, low friction rolling with a friction coefficient of 0.22 or less is performed for one pass or more, and the rolling reduction of the pass for performing low friction rolling is 20% or more. Furthermore, the rolling reduction of the final cold rolling is over 75%. Thus, Patent Document 2 describes that a grain-oriented electrical steel sheet with extremely high magnetic flux density can be manufactured.

  In the method for producing a non-oriented electrical steel sheet disclosed in Patent Document 3, by weight percent, Si: 0.1 to 7%, Mn: 0.1 to 1.5%, C: 0.005% or less, N : A steel slab containing 0.005% or less and S: 0.005% or less, with the balance being Fe and inevitable impurities, is hot rolled to obtain a hot rolled sheet. The hot-rolled sheet is cold-rolled once and then subjected to finish annealing. Or after that, in the manufacturing method of the non-oriented electrical steel sheet which performs a skin pass rolling after that, after finishing hot rolling, it winds by setting the 1st winding temperature as 750 degreeC or more and 1050 degrees C or less. After holding for 30 seconds or more and 90 minutes or less, rewinding and cooling are performed. Then, it winds up again at the temperature of 550 degrees C or less. Thus, Patent Document 3 describes that a non-oriented electrical steel sheet having a high magnetic flux density can be manufactured.

  In the method for producing a non-oriented electrical steel sheet disclosed in Patent Document 4, a silicon-containing steel slab is hot-finished and subsequently hot-rolled after heating. Then, the final thickness is obtained by cold rolling twice or once with intermediate annealing. Then, when producing a unidirectional silicon steel sheet by a series of processes for performing decarburization annealing and final finish annealing, in the hot finish rolling process, at least one of the passes with an entry side plate thickness of 10 mm or less is advanced rate : Rolled under conditions of 5.0% or more and 10% or less. Thus, Patent Document 4 describes that a unidirectional silicon steel sheet having excellent magnetic properties can be manufactured.

  Patent document 5 and patent document 6 implement special finish hot rolling in order to improve electromagnetic characteristics in manufacture of a steel pipe.

In the method for manufacturing a steel pipe disclosed in Patent Document 5, a steel pipe having a composition containing, by mass%, C: 0.5% or less and Fe of 85% or more is heated. After the heating, in performing the diameter reduction rolling, the diameter reduction rolling is performed at a diameter reduction ratio of 15% or more and a rolling end temperature of (Ar ₃ transformation point −10) ° C. or less. Thus, Patent Document 5 describes that a steel pipe having excellent electromagnetic characteristics can be manufactured.

In the method of manufacturing a steel pipe disclosed in Patent Document 6, in mass%, C: 0.0001 to 0.010%, Si: 0.001 to 0.50%, Mn: 0.01 to 0.50%, P: 0.0001 to 0.05%, S: 0.010% or less, Al: 0.0001% or more and less than 0.01%, N: 0.0001 to 0.01%, the remainder Fe and inevitable The steel pipe having a composition composed of impurities is subjected to reduction rolling and annealing treatment. In the diameter reduction rolling, the steel pipe is heated to a heating temperature: Ac ₃ transformation point or higher and 1100 ° C. or lower, and the diameter reduction ratio: 15% or higher, and the diameter reduction rolling end temperature: (Ar ₃ transformation point−100 ° C.) or higher is Ar ₃ transformation point. Rolling to be less than. Thus, Patent Document 6 describes that a steel pipe excellent in magnetic shield characteristics can be manufactured.

JP-A-9-217117 JP-A-11-050151 JP 2001-098325 A JP-A-4-124219 Japanese Patent Laid-Open No. 2005-281853 Japanese Patent Laying-Open No. 2015-78412

  However, in the manufacturing method of Patent Document 1, the magnetic properties may be lower than the magnetic properties of the non-oriented electrical steel sheet that has been subjected to hot-rolled sheet annealing by line annealing.

  Since the manufacturing method of patent document 2 is related to a grain-oriented electrical steel sheet, in a non-oriented electrical steel sheet, a magnetic characteristic may be inadequate.

  In the manufacturing method of Patent Document 3, the magnetic properties may be lower than the magnetic properties of the non-oriented electrical steel sheet subjected to hot-rolled sheet annealing by line annealing.

  In the manufacturing method of Patent Document 4, the texture of the primary recrystallized plate, which is an intermediate product of grain-oriented electrical steel sheets, has many {110} planes. Among them, there are many {110} <001> orientations that serve as nuclei for secondary recrystallization of grain-oriented electrical steel sheets. In this case, the magnetic properties in the sheet width direction are significantly inferior to the magnetic properties in the rolling direction.

  The manufacturing methods of Patent Document 5 and Patent Document 6 are intended for steel pipes, and are not easy to apply to non-oriented electrical steel sheets used for motors and small iron cores.

  On the other hand, non-oriented electrical steel sheets used for motor iron cores are also required to have a high yield. For example, in a drive motor of an automobile, a stator and a rotor are taken together from one non-oriented electrical steel sheet. Further, an accessory core having a smaller diameter is punched from the remaining material on the inner periphery. This increases the yield.

  In the case of co-taking, if the difference between the magnetic characteristics in the rolling direction and the sheet width direction is large, the anisotropy of the magnetic characteristics increases. In this case, the yield at the time of material punching decreases. Therefore, non-oriented electrical steel sheets are required not only to have excellent magnetic properties but also to have low magnetic property anisotropy. In said patent document 1-patent document 6, the anisotropy of a magnetic characteristic is not examined.

  An object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties and low magnetic flux density anisotropy.

The non-oriented electrical steel sheet according to the present invention is in mass%, Si: 0.1 to 3.8%, Mn: 0.1 to 2.5%, Al: 0 to 2.5%, C: 0 to 0. 0.003%, P: 0 to 0.25%, S: 0 to 0.003%, N: 0 to 0.003%, Ti: 0 to 0.004%, Nb: 0 to 0.003% , As: 0 to 0.003%, and Zr: 0 to 0.003%, and the balance has a chemical composition composed of Fe and impurities. The magnetic flux density B _{50 (LC),} which is an average value of the magnetic flux density B _{50 (L) in the} rolling direction and the magnetic flux density B _{50 (C)} in the direction perpendicular to the rolling direction, is 1.700 T or more. The anisotropy index B50 (anisotropy) defined by the following formula (1) is less than 0.020.

Here, B ₅₀ (0 °), B ₅₀ (22.5 °), B ₅₀ (45 °), B ₅₀ (67.5 °) and B ₅₀ (90 °) are respectively in the rolling direction. Then, the value of each magnetic flux density B _{50 in} the direction of angles of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° is substituted. In the formula (1), B _50ave is a value defined by the following formula (2).

  The non-oriented electrical steel sheet of the present invention is excellent in magnetic properties and has low anisotropy.

FIG. 1 is a diagram showing the relationship between the angle (°) with respect to the rolling direction and the magnetic flux density (T) at each angle, that is, the anisotropy of the magnetic flux density, in a non-oriented electrical steel sheet. FIG. 2 is a diagram showing the relationship between the angle (°) with respect to the rolling direction and the magnetic flux density (T) at each angle, that is, the anisotropy of the magnetic flux density, in another non-oriented electrical steel sheet. FIG. 3 is a diagram showing the relationship between the angle (°) with respect to the rolling direction and the magnetic flux density (T) at each angle, that is, the anisotropy of the magnetic flux density, in another non-oriented electrical steel sheet.

  Hereinafter, the present invention will be described in detail.

  The present inventors have investigated and studied a method for producing a hot-rolled steel sheet for non-oriented electrical steel sheets that affects magnetic characteristics (iron loss and magnetic flux density) and anisotropy of magnetic characteristics. As a result, the following knowledge was obtained.

  Non-oriented electrical steel sheets are used by being laminated. When the non-oriented electrical steel sheet is deformed and laminated, the magnetic properties are deteriorated. Therefore, conventionally, the final pass of the finish hot rolling of the non-oriented electrical steel sheet has been performed under conditions for controlling the shape of the non-oriented electrical steel sheet. When the reduction ratio in the final pass of finish hot rolling is set to 20% or more as in Patent Document 2, it is difficult to control the thickness of the hot rolled steel strip for non-oriented electrical steel sheets. Therefore, normally, in the final pass of finish hot rolling, light reduction with a reduction ratio of about 10% is performed. However, the magnetic characteristics are not improved under such light pressure.

  On the other hand, the present inventors considered utilizing the final pass of the finish hot rolling process as a process for enhancing magnetic properties. Therefore, the present inventors further investigated and examined the manufacturing conditions in the final pass in the finishing hot rolling process for enhancing the magnetic properties. As a result, the following knowledge was obtained.

  In the final pass of the finish hot rolling process, if the rolling reduction was increased and the strong rolling was performed, the magnetic properties were enhanced. Therefore, in the finish hot rolling process, the rolling reduction of the final pass is significantly increased as compared with the conventional method. Specifically, the rolling reduction of the final pass is set to 80% or more.

  In addition, as mentioned above, normally, when the reduction ratio was 20% or more, it was considered difficult to control the thickness of the hot-rolled steel strip for non-oriented electrical steel sheets, The shape could also be controlled. The reason is considered as follows. If the rolling reduction of the final pass is 80% or more, processing heat generation occurs and deformation resistance decreases. If the deformation resistance decreases, the thickness of the hot-rolled steel strip for non-oriented electrical steel sheet can be controlled even if the rolling reduction is high.

  In the final pass of the finishing hot rolling process, the advanced rate is further increased more than usual. The advanced rate is the ratio of the rolled sheet speed (sheet speed) on the outlet side to the roll circumferential speed. That is, in the final pass of the finish hot rolling process, the final pass is performed so as to extrude the rolled plate with a roll. The advanced rate in the final pass of the conventional finish hot rolling process is about 3 to 6%. However, in the present embodiment, the advanced rate is set to more than 10% and 500% or less.

  Furthermore, the tension | tensile_strength of 20 Mpa or more and 100 Mpa or less is provided to the rolling plate after the last stand passage. Although the detailed mechanism by this is unknown, the anisotropy of the magnetic properties of the non-oriented electrical steel sheet can be reduced by the correlation with the cooling rate control immediately after passing through the final stand.

  Further, the cooling process after passing through the final stand is rapid cooling. Specifically, the cooling rate immediately after passing through the final stand is set to 20 ° C./s or more and 200 ° C./s or less. Thereby, recrystallization of the surface layer of the hot-rolled steel strip for non-oriented electrical steel sheets is suppressed.

  It has been found that the magnetic characteristics (iron loss and magnetic flux density) are increased and the anisotropy of the magnetic flux density is reduced by the manufacturing conditions in the above finish hot rolling process.

  The inventors further investigated the relationship between the manufacturing conditions and the magnetic flux density anisotropy in the finish hot rolling step according to the present embodiment described above.

  As a result, the non-oriented electrical steel sheet manufactured by the manufacturing conditions according to the present embodiment has a small magnetic flux density anisotropy, and the non-oriented electrical steel sheet manufactured by the manufacturing method deviating from the manufacturing conditions according to the present embodiment It was found that the anisotropy of magnetic flux density was large.

  As described above, if all the manufacturing conditions in the finish hot rolling process according to the present embodiment are satisfied, not only the magnetic characteristics are improved, but also the anisotropy of the magnetic flux density is reduced.

  Although it is not certain about the above-mentioned mechanism, the present inventors speculate as follows. In the final pass of the finish hot rolling process under the above-described conditions, rolling is performed so that the roll extrudes the hot-rolled steel strip in the final stand at a high reduction rate and a high advanced rate, which are not conventional in the present invention. Thereby, a shear strain (hereinafter referred to as additional strain) that is not introduced into the center layer of the plate thickness is introduced in a novel form into the crystal structure of the surface layer of the hot-rolled steel strip for non-oriented electrical steel sheets. Due to the processing heat generation, recrystallization proceeds in the thickness center layer of the hot-rolled steel strip for non-oriented electrical steel sheets. However, the surface layer of the hot-rolled steel strip for non-oriented electrical steel sheets is subjected to heat removal from the roll in the final stand and immediately after cooling. Therefore, in the surface layer of the hot-rolled steel strip for non-oriented electrical steel sheets, the crystal structure having the additional strain in the form that cannot be obtained by the above-described prior art is maintained without being affected by the processing heat generation.

  Although the mechanism by said result is not certain, inventors guess that a magnetic characteristic will increase as a result of the effect with respect to the surface layer and center layer by said manufacturing process.

  Further, regarding the texture formation mechanism in the present invention, the primary recrystallization orientation generated from the crystal structure having the additional strain is the GOSS orientation ({110} <001> orientation having one easy magnetization axis). Accumulation in is small. As a result, the inventors speculate that the anisotropy of the magnetic flux density becomes small.

The non-oriented electrical steel sheet according to the present invention completed on the basis of the above knowledge is in mass%, Si: 0.1 to 3.8%, Mn: 0.1 to 2.5%, Al: 0 to 2. 5%, C: 0 to 0.003%, P: 0 to 0.25%, S: 0 to 0.003%, and N: 0 to 0.003%, Ti: 0 to 0.004%, Nb: 0 to 0.003%, As: 0 to 0.003%, and Zr: 0 to 0.003%, with the balance having a chemical composition composed of Fe and impurities. The magnetic flux density B _{50 (LC),} which is an average value of the magnetic flux density B _{50 (L) in the} rolling direction and the magnetic flux density B _{50 (C)} in the direction perpendicular to the rolling direction, is 1.700 T or more. The anisotropy index B50 (anisotropy) defined by the following formula (1) is less than 0.020.

Here, B ₅₀ (0 °), B ₅₀ (22.5 °), B ₅₀ (45 °), B ₅₀ (67.5 °) and B ₅₀ (90 °) are respectively in the rolling direction. Then, the value of each magnetic flux density B _{50 in} the direction of angles of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° is substituted. In the formula (1), B _50ave is a value defined by the following formula (2).

  The non-oriented electrical steel sheet manufacturing method according to the present invention includes a hot rough rolling process in which a hot rough rolling is performed on a material to manufacture a rolled sheet, and a finish hot rolling is performed on the rolled sheet. And cold rolling to produce hot-rolled steel strip for non-oriented electrical steel sheet and cold-rolled steel sheet for cold-rolled steel strip for non-oriented electrical steel sheet A cold rolling process to perform, and a finish annealing process to perform finish annealing on the cold-rolled steel sheet. In the final hot rolling process, the rolling reduction of the final pass is 80% or more and 95% or less, the advanced rate of the final pass is more than 10% and 500% or less, and for the rolled plate after passing through the final stand, A tension of 20 MPa or more and 100 MPa or less is applied, and cooling is performed at a cooling rate of 20 ° C./s or more and 200 ° C./s or less.

  The manufacturing method of said non-oriented electrical steel sheet may further comprise a hot-rolled sheet annealing step for performing hot-rolled sheet annealing on the hot-rolled steel strip for non-oriented electrical steel sheet. In this case, the magnetic flux density is further increased while maintaining the characteristic of low magnetic property anisotropy, which is a feature of the present invention.

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

[Chemical composition]
The chemical composition of the non-oriented electrical steel sheet according to the present invention preferably contains the following elements. In addition, “%” in the chemical composition of the non-oriented electrical steel sheet and the hot-rolled steel strip for non-oriented electrical steel sheet means mass% unless otherwise specified. In the present embodiment, the slab, the hot-rolled steel strip for non-oriented electrical steel sheet, and the non-oriented electrical steel sheet have the same composition.

Si: 0.1 to 3.8%
Silicon (Si) increases the specific resistance of the steel sheet and reduces iron loss. Si further reduces hysteresis loss. If the Si content is less than 0.1%, the above effect cannot be obtained. On the other hand, if the Si content exceeds 3.8%, the rollability in hot rolling described later and the magnetic properties of the non-oriented electrical steel sheet may be deteriorated. If Si content exceeds 3.8%, the below-mentioned finish annealing temperature will rise further. Therefore, the Si content is 0.1 to 3.8%. The minimum with preferable Si content is 1.0%, More preferably, it is 2.0%. The upper limit with preferable Si content is 3.6%, More preferably, it is 3.4%.

Mn: 0.1 to 2.5%
Manganese (Mn) increases the specific resistance of steel and reduces iron loss. If the Mn content is less than 0.1%, these effects cannot be obtained. On the other hand, if the Mn content exceeds 2.5%, the recrystallized structure is refined and the iron loss increases. Therefore, the Mn content is 0.1 to 2.5%. The minimum with preferable Mn content is 0.5%. The upper limit with preferable Mn content is 1.3%.

  The balance of the chemical composition of the non-oriented electrical steel sheet according to the present invention consists of Fe and impurities. Here, an impurity is a thing mixed from the ore as a raw material, a scrap, or a manufacturing environment when manufacturing a non-oriented electrical steel sheet industrially.

  Impurities in the present embodiment are, for example, C, P, S, N, Ti, Nb, As, and Zr.

C: 0 to 0.003%
Carbon (C) is an impurity. C may cause fine carbides to precipitate in the steel and reduce the magnetic properties. Therefore, the C content is 0 to 0.003%. The lower limit of the C content is not particularly limited. Considering the refining cost, C may be contained less than 0.004%. If C is contained in an amount of 0.004% or more, magnetic aging occurs during use of the non-oriented electrical steel sheet, and iron loss increases, so the C content should not exceed 0.004%. The upper limit with preferable C content is 0.002%, More preferably, it is 0.001%.

P: 0 to 0.25%
Phosphorus (P) is an impurity. P can degrade the magnetic properties. Therefore, the P content is 0 to 0.25%. The P content is preferably as low as possible. The lower limit of the P content is not particularly limited. The upper limit with preferable P content is 0.10%, More preferably, it is 0.05%.

S: 0 to 0.003%
Sulfur (S) is an impurity. S produces MnS and increases iron loss. Therefore, the S content is 0 to 0.003%. The S content is preferably as low as possible. The lower limit of the S content is not particularly limited. Considering the refining cost, S may be contained by 0.004%. However, from the viewpoint of reducing iron loss, it is necessary to be 0.003% or less. The upper limit with preferable S content is 0.002%, More preferably, it is 0.001%.

N: 0 to 0.003%
Nitrogen (N) is an impurity. N precipitates fine AlN and can degrade the magnetic properties. Therefore, the N content is 0 to 0.003%. The N content is preferably as low as possible. The lower limit of the N content is not particularly limited. The upper limit with preferable N content is 0.002%, More preferably, it is 0.001%.

Ti: 0 to 0.004%
Titanium (Ti) is an impurity. Ti can degrade the magnetic properties. Therefore, the Ti content is 0 to 0.004%. The Ti content is preferably as low as possible. The lower limit of the Ti content is not particularly limited. The upper limit with preferable Ti content is 0.003%, More preferably, it is 0.002%.

Nb: 0 to 0.003%
Niobium (Nb) is an impurity. Nb can degrade the magnetic properties. Therefore, the Nb content is 0 to 0.003%. The Nb content is preferably as low as possible. The lower limit of the Nb content is not particularly limited. The upper limit with preferable Nb content is 0.002%, More preferably, it is 0.001%.

As: 0 to 0.003%
Arsenic (As) is an impurity. As can degrade the magnetic properties. Therefore, the As content is 0 to 0.003%. The As content is preferably as low as possible. The lower limit of the As content is not particularly limited. The upper limit with preferable As content is 0.002%, More preferably, it is 0.001%.

Zr: 0 to 0.003%
Zirconium (Zr) is an impurity. Zr can degrade the magnetic properties. Therefore, the As content is 0 to 0.003%. The Zr content is preferably as low as possible. The lower limit of the Zr content is not particularly limited. The upper limit with preferable Zr content is 0.002%, More preferably, it is 0.001%.

  The content of the impurities is allowed in a range that does not adversely affect the non-oriented electrical steel sheet of the present embodiment. The total content of impurities is preferably 0.1% or less. A more preferable upper limit of impurities is 0.01% in total.

[Arbitrary elements]
The chemical composition of the non-oriented electrical steel sheet of the present invention may further contain Al instead of a part of Fe.

Al: 0 to 2.5%
Aluminum (Al) is an optional element. When included, Al deoxidizes the steel. Further, Al coarsens the nitride and renders it harmless. However, if the Al content exceeds 2.5%, the iron loss can be increased. Therefore, the Al content is 0 to 2.5%. The minimum with preferable Al content is 0.3%, More preferably, it is 0.9%. The upper limit with preferable Al content is 2.3%, More preferably, it is 2.0%.

[Magnetic flux density B _{50 (LC)} : 1.700 T or more]
The magnetic flux density B _{50 (LC)} of the non-oriented electrical steel sheet according to the present embodiment is 1.700 T or more. Therefore, the non-oriented electrical steel sheet according to the present embodiment is excellent in magnetic properties. The magnetic flux density B _{50 (LC)} can be measured as follows.

[Magnetic flux density B _{50 (LC)} measurement method]
In a non-oriented electrical steel sheet, magnetic flux density B _{50 (L)} in the L direction (rolling direction) and magnetic flux density B _{50 (} C _{) in the} C direction (direction orthogonal to the rolling direction ₎ are measured. Specifically, Epstein test pieces are cut out from the non-oriented electrical steel sheets of the respective test numbers in the L direction and the C direction in accordance with JIS C 2550-1 (2011). An electromagnetic steel strip test method based on JIS C 2550-1 (2011) and 2550-3 (2011) is performed on the cut Epstein test piece, and the magnetic flux density B at 5000 A / m in the L direction and the C direction. ₅₀ is measured. The magnetic flux density B _{50 (LC)} is obtained as an average value of the magnetic flux density B _{50 (L) in the L} direction and the magnetic flux density B _{50 (C) in} the C direction.

[Anisotropy of magnetic flux density B50 (anisotropy): less than 0.020]
The anisotropy B50 (anisotropy) of the magnetic flux density of the non-oriented electrical steel sheet according to the present embodiment is less than 0.020. Therefore, the non-oriented electrical steel sheet according to the present embodiment has a small magnetic flux density anisotropy. The anisotropy B50 (anisotropy) of the magnetic flux density of the non-oriented electrical steel sheet is determined as follows.

[Method of evaluating magnetic flux density anisotropy B50 (anisotropy)]
An Epstein sample is taken from a non-oriented electrical steel sheet. The direction of the Epstein sample to be collected is set to 0 ° in the rolling direction and clockwise at intervals of 22.5 ° from the rolling direction. The magnetic flux density B ₅₀ of the Epstein samples measured. Each magnetic flux density B ₅₀ in the direction of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° with respect to the rolling direction is set to B ₅₀ (0 °), B ₅₀ (22.5 °), B ₅₀ (45 °), B ₅₀ (67.5 °), and B ₅₀ (90 °). B _50ave is determined by the following equation (2).

  Anisotropy index B50 (anisotropy) is obtained by the following formula (1).

[Average crystal grain size]
Preferably, furthermore, the average grain size of the non-oriented electrical steel sheet according to the present embodiment is 30 to 200 μm. If the average crystal grain size is 30 μm or more, in the non-oriented electrical steel sheet, the hysteresis loss is reduced and the iron loss is reduced. If the average crystal grain size is 200 μm or less, the processability such as punching is excellent. A more preferable average crystal grain size is 50 to 150 μm.

  The average crystal grain size means a value obtained by measuring and averaging the diameters of circles of the same area with respect to the projected area for a plurality of crystal grains observed in the non-oriented electrical steel sheet.

  As the average grain size of the non-oriented electrical steel sheet, the equivalent circle diameter obtained by the following method is used in the present invention.

  Specifically, the average cross-sectional area of the crystal grains obtained by the line segment method defined in JIS G 0552 is converted into a circle equivalent and the diameter is obtained. At this time, the observation visual field is a cross section including the rolling direction and the sheet width direction. This cross section is etched by chemical polishing methods such as mechanical polishing and nital etching, grain boundaries are revealed, a photograph is taken with an optical microscope, and a line segment method is used to obtain the equivalent circle diameter based on the photograph. .

  Alternatively, the equivalent circle diameter may be obtained by applying a line segment method defined in JIS G 0552 to the same cross section using a photograph obtained by observation with an electron microscope.

  Further, the equivalent circle diameter may be obtained based on an optical micrograph or an electron micrograph by image processing.

[Method for producing non-oriented electrical steel sheet]
The manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated. The non-oriented electrical steel sheet of the present invention is manufactured by performing a cold rolling process and a finish annealing process on a hot-rolled steel strip for a non-oriented electrical steel sheet.

[Method for producing hot-rolled steel strip for non-oriented electrical steel sheet]
The method for producing a hot-rolled steel strip for non-oriented electrical steel sheets according to the present invention includes a hot rough rolling process in which hot rough rolling is performed on a material to produce a rolled plate, and the rolled plate is finished. A finishing hot rolling process for performing hot rolling. In the finish hot rolling step, the rolling reduction of the final pass is 80% or more and 95% or less, and the advanced rate of the final pass is more than 10% and 500% or less. In the finish hot rolling step, a tension of 20 MPa or more and 100 MPa or less is further applied to the rolled plate after passing through the final stand. Further, cooling of the rolled plate after passing through the final stand is performed at a cooling rate of 20 ° C./s or more and 200 ° C./s or less after passing through the final stand.

[Hot rough rolling process]
In the hot rough rolling step, hot rough rolling is performed on the slab to produce a rough rolled plate. The slab preferably has the chemical composition described above. The slab is manufactured by a known method. For example, a slab is manufactured by a continuous casting method using a molten metal having the above chemical composition. An ingot may be manufactured by the ingot-making method using the molten metal having the above chemical composition, and the ingot may be subjected to ingot rolling to manufacture a slab. You may implement partial rolling with respect to the slab manufactured by the continuous casting method.

  Hot rough rolling is performed on the prepared slab using a rough hot rolling machine. Various conditions in the hot rough rolling are not particularly limited. The slab heating temperature during hot rough rolling is not particularly limited. From the viewpoint of cost and hot rollability, the slab heating temperature is preferably 900 ° C. or higher and 1250 ° C. or lower. A more preferable lower limit of the slab heating temperature is 950 ° C. A more preferable upper limit of the slab heating temperature is 1150 ° C.

  As the rough hot rolling machine, for example, a multi-stage hot rolling machine having a plurality of stands is used. For example, a method of performing reciprocating or unidirectional rolling by a two-stage or four-stage hot rolling machine having 1 to 6 stands is mentioned.

  The rolling reduction of the hot rough rolling is not particularly limited as long as the effect of the present embodiment can be obtained, but is 55% or more and 90% or less. The more preferable lower limit of the rolling reduction of the hot rough rolling is 70%. A more preferable upper limit of the reduction ratio of the hot rough rolling is 85%.

  Furthermore, a rough rolled plate may be obtained directly by thin cast casting by a twin roll method or the like. In the case of thin slab production, component measurement is performed by collecting molten metal poured into a tundish. According to the inventors' investigation, it has been found that rolling is not necessarily required for thin cast slabs. The reason why rolling is not necessary for thin cast slabs is not clear, but is considered as follows. There is a possibility that the texture and crystal structure of the hot-rolled steel strip are appropriately controlled because the distribution of the rolling ratio in the finish rolling according to the present invention is different from usual.

[Finish hot rolling process]
In the finish hot rolling step, the obtained rolled plate is subjected to finish hot rolling by a finish hot rolling mill to produce a hot-rolled steel strip for non-oriented electrical steel sheets.

  In the finishing hot rolling process, even if a plurality of passes are performed, tandem rolling is performed using a tandem rolling mill including a plurality of rolling stands arranged in a row (each rolling stand has a pair of work rolls). Alternatively, a plurality of passes may be performed by performing reverse rolling using a Sendzimir rolling mill or the like having a pair of work rolls.

[Rolling ratio of final hot rolling roll: 80% or more and 95% or less]
The rolling reduction of the final pass of finish hot rolling is 80% or more and 95% or less. Note that the rolling reduction (%) of the final pass is defined as follows.
Reduction ratio of final pass = (1−thickness of hot-rolled steel strip for non-oriented electrical steel sheet after final pass of finishing hot rolling step / thickness of rolled plate before final pass) × 100

  If the rolling reduction of the final pass is 80% or more, processing heat is generated and deformation resistance decreases. If the deformation resistance is reduced, it is possible to control the thickness of the hot-rolled steel strip for non-oriented electrical steel sheets even at a high pressure reduction rate.

  If the rolling reduction ratio of the final pass is 80% or more, additional strain in a form unconventional is introduced into the crystal structure of the hot-rolled steel strip for non-oriented electrical steel sheets. As a result, the magnetic characteristics are enhanced.

  If the rolling reduction in the final pass of the finish hot rolling is less than 80%, the magnetic properties are deteriorated. If the rolling reduction in the final pass of the finish hot rolling is less than 80%, the anisotropy of the magnetic flux density is further increased. On the other hand, if the rolling reduction in the final pass of finish hot rolling exceeds 95%, the effect of enhancing the magnetic properties is saturated. If the rolling reduction of the final pass of finish hot rolling exceeds 95%, the roll load of the rolling mill is further increased. Therefore, the rolling reduction of the final pass of finish hot rolling is 80% or more and 95% or less. A preferable lower limit of the rolling reduction in the final pass of the finish hot rolling is 81%, and more preferably 82%. A preferable upper limit of the rolling reduction in the final pass of the finish hot rolling is 90%, and more preferably 85%.

[Advanced rate of final hot rolling pass: Over 10% and under 500%]
The advanced rate of the final pass of finish hot rolling is more than 10% and not more than 500%. As a result, a large shear force is applied, and additional strain is introduced into the crystal structure. As a result, the magnetic characteristics are enhanced.

The advanced rate is the ratio of the rolled sheet speed (sheet speed) on the outlet side to the roll circumferential speed. In other words, the advanced rate (%) of the final path is defined as follows.
Advanced rate of final pass = ((plate speed at exit of final pass (m / s) −roll peripheral speed (m / s)) / roll peripheral speed (m / s)) × 100

  If the advanced rate of the final pass of the finish hot rolling is 10% or less, the magnetic properties are deteriorated. If the advanced rate of the final pass of finish hot rolling is 10% or less, the anisotropy of magnetic flux density is further increased. On the other hand, if the advanced rate of the final pass of the finish hot rolling exceeds 500%, the magnetic properties are deteriorated. If the advanced rate of the final pass of finish hot rolling exceeds 500%, the anisotropy of magnetic flux density further increases. If the advanced rate of the final pass of finish hot rolling exceeds 500%, rolling in the final pass becomes more difficult. Therefore, the advanced rate of the final pass of finish hot rolling is more than 10% to 500% or less. A preferable lower limit of the advanced rate of the final pass of the finish hot rolling is 20%. The upper limit of the advanced rate of the final pass of the finish hot rolling is preferably 300%, more preferably 200%.

  Preferably, the finish hot rolling temperature is 800 ° C. or higher and 1050 ° C. or lower. The finish hot rolling temperature means the surface temperature of the rolled sheet during finish hot rolling. The surface temperature of the rolled sheet is measured, for example, with a known radiation thermometer. When the finish hot rolling temperature is 800 ° C. or higher, the rolling reduction of the final pass of finish hot rolling can be 80% or more. If finishing hot rolling temperature is 1050 degrees C or less, when tension | tensile_strength is provided after the last pass of finishing hot rolling, it can suppress that a shape defect generate | occur | produces by extension of a rolled sheet. Here, “pass” means that the rolled plate passes through one rolling stand having a pair of work rolls and is subjected to reduction.

The cumulative reduction ratio in the finish hot rolling step is not particularly limited. The cumulative reduction ratio in the finish hot rolling step is, for example, 80% or more and 98% or less. The cumulative reduction ratio (%) in the finish hot rolling process is defined as follows.
Cumulative rolling reduction in finish hot rolling process = (1−thickness of hot rolled steel strip for non-oriented electrical steel sheet after final pass in finish hot rolling process / rolling before finish hot rolling in first pass Board thickness) x 100

  A preferable lower limit of the cumulative rolling reduction in the finish hot rolling step is 85%. A preferable upper limit of the cumulative rolling reduction in the finish hot rolling step is 97%.

  The thickness of the hot-rolled steel strip for non-oriented electrical steel sheets after finish hot rolling is not particularly limited. The thickness of the hot-rolled steel strip for non-oriented electrical steel sheets after finish hot rolling is, for example, 0.8 mm or more and 3 mm or less. If the thickness of the hot-rolled steel strip for non-oriented electrical steel sheet after finish hot rolling is 0.8 mm or more and 3 mm or less, rapid cooling immediately after the final pass is promoted. The more preferable lower limit of the thickness of the hot-rolled steel strip for non-oriented electrical steel sheets after finish hot rolling is 1.0 mm, and more preferably 1.3 mm. The more preferable upper limit of the thickness of the hot-rolled steel strip for non-oriented electrical steel sheet after finish hot rolling is 2.7 mm, and more preferably 2.3 mm.

[Tension after final pass of finish hot rolling: 20 MPa or more and 100 MPa or less]
In this embodiment, the tension | tensile_strength of 20 Mpa or more and 100 Mpa or less is provided with respect to the rolled sheet after the last pass of finish hot rolling. Thereby, heat can be removed from the roll, and a crystal structure having additional strain can be maintained. As a result, the magnetic characteristics are enhanced.

  The primary recrystallization orientation generated from the crystal structure having the additional strain described above has a small accumulation in the GOSS orientation. As a result, the anisotropy of the magnetic flux density is reduced.

  When the tension applied after the final pass of the finish hot rolling is less than 20 MPa, this effect cannot be obtained. On the other hand, when the tension applied after the final pass of the finish hot rolling exceeds 100 MPa, the effect of enhancing the magnetic properties is saturated. When the tension applied after the final pass of finish hot rolling exceeds 100 MPa, the rolled sheet immediately after passing the final pass is easily deformed. Therefore, the tension | tensile_strength provided with respect to the rolled sheet after the last pass is 20 MPa or more and 100 MPa or less. The minimum with the preferable tension | tensile_strength provided after the final pass of finishing hot rolling is 30 Mpa, More preferably, it is 40 Mpa. The upper limit with the preferable tension | tensile_strength provided after the final pass of finish hot rolling is 90 Mpa, More preferably, it is 80 Mpa.

[Cooling rate after passing through final hot rolling pass: 20 ° C./s or more and 200 ° C./s or less]
In the present embodiment, the rolled plate after passing through the final stand is further cooled at least 600 ° C. at a cooling rate of 20 ° C./s or more and 200 ° C./s or less. After the last stand means immediately after the last stand. Immediately after passing the final stand is, for example, within 3 seconds after passing the final stand. Preferably it is within 2 seconds, more preferably within 1 second. Passing through the stand means the moment when the contact between the hot-rolled steel strip and the rolling roll is completed. Thereby, recrystallization of the surface layer of the hot-rolled steel strip for non-oriented electrical steel sheets can be suppressed, and a crystal structure having additional strain can be further retained. As a result, the magnetic characteristics are enhanced.

  The primary recrystallization orientation generated from the crystal structure having the additional strain described above has a small accumulation in the GOSS orientation. As a result, the anisotropy of the magnetic flux density is reduced.

  This effect cannot be obtained when the cooling rate immediately after passing the final pass of finish hot rolling is less than 20 ° C./s. On the other hand, when the cooling rate immediately after passing through the final pass of finish hot rolling exceeds 200 ° C./s, the rolled sheet is likely to be deformed by cooling strain during cooling. Therefore, the cooling rate immediately after passing the final pass of finish hot rolling is 20 ° C./s or more and 200 ° C./s or less. The preferable lower limit of the cooling rate immediately after passing the final pass of the finish hot rolling is 30 ° C./s, more preferably 40 ° C./s. A preferable upper limit of the cooling rate immediately after passing the final pass of finish hot rolling is 180 ° C./s, and more preferably 160 ° C./s.

  The cooling method after passing through the final pass of the finish hot rolling is not particularly limited. A cooling method after passing through the final pass of finish hot rolling is, for example, air-water cooling. The passing speed at the time of cooling is 600 m / s or more and 1250 m / s or less, for example.

  About the position where the coil winding device for winding the coil is installed, the distance from the final stand of the finishing hot rolling machine used for finishing hot rolling to the coil winding device is generally 100 m or more and 200 m or less. It is. However, in this embodiment, rapid cooling is performed on the rolled plate after passing through the final stand. Furthermore, tension | tensile_strength is provided to the steel plate after passage with respect to the rolled plate after the last stand passage. Therefore, the distance from the final stand of the finishing hot rolling machine to the coil winding device is preferably 20 m or more and 50 m or less. If the distance from the final stand of the finishing hot rolling machine to the coil winding device is within 20 to 50 m, the rolled plate after passing through the final stand can be cooled more precisely and tension can be applied.

  The distance from the final stand of the finishing hot rolling machine to the coil winding device is more preferably 25 m or more and 45 m or less, and further preferably 30 m or more and 40 m or less.

  Although the winding speed to a coil is not specifically limited, For example, it is 500 m / min or more and 1600 m / min or less.

  The winding temperature around the coil is, for example, 750 ° C. or lower. When hot-rolled sheet annealing described below is not performed, the coiling temperature is, for example, 850 ° C. or lower.

  The hot rolling steel strip for non-oriented electrical steel sheets according to the present invention can be manufactured by the above manufacturing process.

  In the method for manufacturing a hot-rolled steel strip for non-oriented electrical steel sheets according to this embodiment, a hot-rolled sheet annealing step may be further performed after the hot rolling step.

[Hot rolled sheet annealing process]
When implementing a hot-rolled sheet annealing process, hot-rolled sheet annealing is implemented with respect to the hot-rolled steel strip for non-oriented electrical steel sheets obtained at the hot rolling process.

  When hot-rolled sheet annealing is performed, for example, the maximum temperature reached is 950 ° C. or higher and 1050 ° C. or lower, and the holding time is 1 second or longer and 180 seconds or shorter. Hot-rolled sheet annealing is performed by a continuous annealing furnace, for example. When the maximum temperature reached and the holding time are within the above ranges, the load on the equipment can be suppressed and the productivity can be improved. Furthermore, the magnetic properties of the non-oriented electrical steel sheet are further enhanced.

[Method for producing non-oriented electrical steel sheet]
The non-oriented electrical steel sheet of the present embodiment is manufactured by further performing the following process using the hot-rolled steel strip for non-oriented electrical steel sheet manufactured in the above process.

[Cold rolling process]
Cold rolling is performed on the hot-rolled steel strip for non-oriented electrical steel sheets obtained in the hot rolling process or the hot-rolled steel strip for non-oriented electrical steel sheets after hot-rolled sheet annealing. Manufacturing cold-rolled steel sheets. Cold rolling may be performed a plurality of times. When cold rolling is performed a plurality of times, intermediate annealing may be performed as necessary. The cold rolling process is not particularly limited as long as the effects of the present embodiment can be obtained. In addition, you may implement pickling to the hot-rolling steel strip for non-oriented electrical steel sheets before cold rolling.

  In cold rolling, the thickness of the cold-rolled steel sheet is preferably 0.1 mm or more and 0.65 mm or less, and more preferably 0.15 or more and 0.35 mm or less.

  The rolling reduction of cold rolling is not particularly limited as long as the effects of the present embodiment can be obtained. The rolling reduction of cold rolling is a cumulative rolling reduction, preferably 50% or more and 97% or less, and more preferably 60 or more and 88% or less. If the rolling reduction of the cold rolling is 50% or more, it becomes easy to obtain appropriate magnetic properties after finish annealing. Moreover, if the rolling reduction of cold rolling is 97% or less, the texture of a non-oriented electrical steel sheet can be controlled appropriately, and it becomes easy to reduce an iron loss.

[Finish annealing process]
A non-oriented electrical steel sheet is manufactured by performing finish annealing on the cold-rolled steel sheet manufactured by performing cold rolling. In the finish annealing, the cold-rolled steel sheet finished to the final thickness is annealed and recrystallized.

  The temperature range and holding time of finish annealing are not particularly limited. The temperature range and holding time of finish annealing are appropriately set according to the chemical composition of the non-oriented electrical steel sheet, the conditions of the hot rolling process, and the finishing rolling process. The temperature range of finish annealing is preferably 700 ° C. or higher and 1100 ° C. or lower. If the temperature range of finish annealing is 700 degreeC or more and 1100 degrees C or less, the oxidation at the time of annealing can be prevented and an iron loss can be reduced. If the temperature range of finish annealing is 700 degreeC or more and 1100 degrees C or less, the coarsening of a crystal grain can be further suppressed and an iron loss can also be reduced. The temperature range of finish annealing is more preferably 750 ° C. or more and 1050 ° C. or less. The holding time in the temperature range of finish annealing is preferably 0.1 seconds or more and 120 seconds or less, and more preferably 10 seconds or more and 60 seconds or less.

  In addition, the temperature range in finish annealing means the surface temperature of the steel plate at the time of finish annealing. The surface temperature of the steel sheet is measured with, for example, a radiation thermometer.

[Other processes]
In the above manufacturing method, the coating step may be performed after the finish annealing step. In the coating process, an insulating coating is applied to the surface of the non-oriented electrical steel sheet after finish annealing. The type of insulating coating is not particularly limited. The insulating coating may be an organic component or an inorganic component. The insulating coating may contain an organic component and an inorganic component. Examples of the inorganic component include dichromic acid-boric acid system, phosphoric acid system, and silica system. The organic component is, for example, a general acrylic resin, acrylic styrene resin, acrylic silicon resin, silicon resin, polyester resin, epoxy resin, or fluorine resin. In consideration of paintability, a preferred resin is an emulsion type resin. You may give the insulating coating which exhibits adhesiveness by heating and / or pressurizing. The insulating coating having adhesive ability is, for example, an acrylic resin, a phenol resin, an epoxy resin, or a melamine resin.

  The non-oriented electrical steel sheet according to the present invention can be manufactured by the above manufacturing process. The non-oriented electrical steel sheet of the present invention is excellent in magnetic properties and has a small magnetic flux density anisotropy.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
The steel slab having the chemical composition shown in steel type A to steel type C in Table 1 was subjected to hot rough rolling to produce a rolled plate. The reheating temperature of the slab was 1100 ° C. In addition, “-” in Table 1 indicates that the content was less than the detection limit. In addition, about content of P, Ti, Nb, As, and Ze, it was 0% or less than said upper limit.

  The obtained rolled plate was subjected to finish hot rolling to produce a hot rolled steel strip for a non-oriented electrical steel sheet. The finish hot rolling conditions were as shown in Table 2. The plate thickness before the start of finish hot rolling was 40 mm, and the thickness of the hot-rolled steel strip for non-oriented electrical steel sheets after hot rolling was 1.6 mm. In addition, about test number 1, test number 4, and test number 7, it was the example of this invention manufactured on the finishing hot rolling conditions by this embodiment. Test numbers 2, 3, 5, 6, 8, and 9 were comparative examples manufactured under conditions that deviated from the finish hot rolling conditions according to the present embodiment.

  In Table 2, hot-rolled sheet annealing was performed on the hot-rolled steel strip for non-oriented electrical steel sheets having the test number described as “Yes” in the column of hot-rolled sheet annealing. The conditions of hot-rolled sheet annealing were as follows: steel type A was held at 800 ° C. for 15 seconds, steel type B was held at 900 ° C. for 30 seconds, and steel type C was held at 950 ° C. for 90 seconds. In Table 2, the hot-rolled sheet annealing was not performed on the hot-rolled steel strip for the non-oriented electrical steel sheet having the test number described as “None” in the column of hot-rolled sheet annealing.

  The obtained hot-rolled steel strip for non-oriented electrical steel sheet was pickled. After pickling, cold rolling was performed to obtain a cold-rolled steel sheet having a thickness of 0.3 mm. The rolling reduction of cold rolling was 81.3%.

  The obtained cold-rolled steel sheet was subjected to finish annealing to obtain a non-oriented electrical steel sheet. The conditions for the finish annealing were held at 750 ° C. for 20 seconds for the cold rolled steel sheets of test numbers 1 to 3. The cold rolled steel sheets of test numbers 4 to 6 were held at 900 ° C. for 20 seconds, and the cold rolled steel sheets of test numbers 7 to 9 were held at 950 ° C. for 30 seconds.

[Magnetic property evaluation test]
[Magnetic flux density measurement test]
For each non-oriented electrical steel sheet obtained, a magnetic flux density B ₅₀ every 22.5 ° from the rolling direction was measured. Specifically, Epstein test pieces cut out at intervals of 22.5 ° from the rolling direction in accordance with JIS C 2550-1 (2011) were prepared from the non-oriented electrical steel sheets of the respective test numbers. Conduct magnetic steel strip test method based on JIS C 2550-1 (2011) and 2550-3 (2011) on Epstein test piece, and magnetic flux density at 5000 A / m every 22.5 ° from rolling direction _B50 was measured. Further, the magnetic flux density B _{50 (LC)} was determined by the above method.

[Anisotropy evaluation test of magnetic flux density]
Furthermore, the magnetic flux density anisotropy was evaluated for each non-oriented electrical steel sheet obtained. The anisotropy of the magnetic flux density was evaluated by an anisotropy index B50 (anisotropy). The anisotropy index B50 (anisotropy) was determined by the above method.

  Table 3 shows the results obtained in the magnetic flux density measurement test and the magnetic flux density anisotropy evaluation test.

  Furthermore, FIGS. 1 to 3 were created based on Table 3. FIG. FIG. 1 shows the relationship between the angle with respect to the rolling direction (angle formed between the sampling direction of the magnetic flux density measurement sample and the rolling direction) (°) and the magnetic flux density (T) at each angle, ie, the magnetic flux density. It is a figure which shows anisotropy. 2 and 3 are also diagrams showing the same relationship for steel types B and C, respectively.

  With reference to Table 3 and FIGS. 1-3, in each steel type, the non-oriented electrical steel sheet manufactured by the manufacturing conditions according to the present embodiment has an anisotropy index value B50 (anisotropy) of less than 0.02. became. The non-oriented electrical steel sheet manufactured by the manufacturing method deviating from the manufacturing conditions according to the present embodiment had an anisotropy index B50 (anisotropy) value of 0.02 or more. Therefore, the non-oriented electrical steel sheet that satisfies the manufacturing conditions of the present invention has a lower anisotropy index B50 (anisotropy) and a lower magnetic flux density anisotropy than the comparative example.

(Example 2)
Hot rough rolling was performed on slabs (steel pieces) having chemical compositions of steel types A to C in Table 1 to produce rolled sheets. The reheating temperature of the slab was 1100 ° C.

  The obtained rolled plate was subjected to finish hot rolling under the conditions shown in Table 4 to produce a hot rolled steel strip for non-oriented electrical steel sheets. In addition, the plate | board thickness of the rolled plate before finish hot rolling was 40 mm in the test number 10-the test number 12, 45 mm in the test number 13-the test number 20, and 40 mm in the test number 21-the test number 25. The thickness of the hot-rolled steel strip for non-oriented electrical steel sheets after finish hot rolling was 2.0 mm.

  In Table 4, the hot-rolled steel strip for the non-oriented electrical steel sheet whose hot-rolled sheet annealing column is “None” was not pickled but was pickled. A cold rolling process and a finish annealing process were performed on the hot-rolled steel strip for non-oriented electrical steel sheets after pickling. The cold rolling was performed by a single method so that the plate thickness was 0.5 mm. The final annealing condition was 750 ° C. for 15 seconds.

  In Table 4, for the hot rolled steel strip for non-oriented electrical steel sheets whose hot rolled sheet annealing column is “Yes”, steel grade A is 800 ° C. for 15 seconds, steel grade B is 900 ° C. for 60 seconds, and steel grade C is 950. Hot rolled sheet annealing was carried out at 90 ° C. for 90 seconds. The hot-rolled steel strip for non-oriented electrical steel sheet after hot-rolled sheet annealing was subjected to pickling, cold rolling process and finish annealing process. The cold rolling was performed by a single method so that the plate thickness was 0.5 mm. The final annealing conditions were as follows: steel type A at 750 ° C. for 15 seconds, steel type B at 900 ° C. for 20 seconds, and steel type C at 950 ° C. for 20 seconds.

  A non-oriented electrical steel sheet was manufactured by the above manufacturing process.

[Magnetic property evaluation test]
[Magnetic flux density measurement test]
In the non-oriented electrical steel sheet of each test number, the magnetic flux density B _{50 (LC)} was determined by the above method.

[Iron loss evaluation test]
An Epstein specimen was prepared in the same manner as the magnetic flux density measurement. The Epstein test piece is subjected to the electromagnetic steel strip test method based on JIS C 2550-1 (2011) and 2550-3 (2011), and is L direction (rolling direction) and C direction (perpendicular to the rolling direction). Direction) of iron loss W _15/50 at 50 Hz and 1.5 _T. Iron loss _W of the L direction (rolling direction) _{15/50 (L)} and C-direction iron losses _{W 15/50} as the mean value of the iron loss _{W 15/50} (in the direction perpendicular to the rolling direction) _{(C) (LC)} Asked.

[Anisotropy evaluation test of magnetic flux density]
The anisotropy of the magnetic flux density was evaluated by an anisotropy index B50 (anisotropy). The anisotropy index B50 (anisotropy) was determined by the above method.

[result]
The evaluation results are shown in Table 5.

  Referring to Table 5, in test number 10, test number 13 to test number 17, and test number 25, the finish hot rolling conditions were appropriate. Therefore, in test number 10, the magnetic flux density was higher, the iron loss was lower, and the anisotropy index B50 (anisotropy) was lower than in test numbers 11 and 12. In test numbers 13 to 17, the magnetic flux density was higher, the iron loss was lower, and the anisotropy index B50 (anisotropy) was lower than in test numbers 18 to 20. Further, in test number 25, the magnetic flux density was higher, the iron loss was lower, and the anisotropy index B50 (anisotropy) was lower than in test numbers 21 to 24. That is, in Test No. 10, Test No. 13 to Test No. 17 and Test No. 25, excellent magnetic properties were obtained and the magnetic flux density anisotropy was small.

  On the other hand, the finishing hot rolling conditions of Test No. 11, Test No. 12, Test No. 18 to Test No. 20, and Test No. 21 to Test No. 24 were inappropriate. Therefore, in the test number 11, the test number 12, the test number 18 to the test number 20, and the test number 21 to the test number 24, the magnetic characteristics were low and the anisotropy of the magnetic flux density was large.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such examples. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

Claims (3)

Non-oriented electrical steel sheet,
% By mass
Si: 0.1 to 3.8%,
Mn: 0.1 to 2.5%
Al: 0 to 2.5%,
C: 0 to 0.003%,
P: 0 to 0.25%
S: 0 to 0.003%, and
N: 0 to 0.003%,
Ti: 0 to 0.004%,
Nb: 0 to 0.003%,
As: 0 to 0.003%, and
Zr: 0 to 0.003%, the balance has a chemical composition consisting of Fe and impurities,
The magnetic flux density B _{50 (LC),} which is the average value of the magnetic flux density B _{50 (L) in the} rolling direction and the magnetic flux density B _{50 (C)} in the direction perpendicular to the rolling direction, is 1.700 T or more. A non-oriented electrical steel sheet having an anisotropy index B50 (anisotropy) defined by) of less than 0.020.
Here, B ₅₀ (0 °), B ₅₀ (22.5 °), B ₅₀ (45 °), B ₅₀ (67.5 °) and B ₅₀ (90 °) are respectively in the rolling direction. Then, the value of each magnetic flux density B _{50 in} the direction of angles of 0 °, 22.5 °, 45 °, 67.5 °, and 90 ° is substituted. In the formula (1), B _50ave is a value defined by the following formula (2).
It is a manufacturing method of the non-oriented electrical steel sheet according to claim 1,
A hot rough rolling process for producing a rolled plate by performing hot rough rolling on the material;
A finish hot rolling step for producing a hot rolled steel strip for a non-oriented electrical steel sheet by performing finish hot rolling on the rolled plate,
For the non-oriented electrical steel sheet hot-rolled steel strip, a cold rolling process for producing a cold-rolled steel sheet by performing cold rolling,
A finish annealing step for performing finish annealing on the cold-rolled steel sheet,
In the finish hot rolling step,
The rolling reduction of the final pass is 80% or more and 95% or less,
The advanced rate of the final pass is over 10% and below 500%,
A method for producing a non-oriented electrical steel sheet, wherein a tension of 20 MPa or more and 100 MPa or less is applied to the rolled plate after passing through the final stand, and cooling is performed at a cooling rate of 20 ° C./s or more and 200 ° C./s or less. . The method for producing a non-oriented electrical steel sheet according to claim 2, further comprising a hot-rolled sheet annealing step for performing hot-rolled sheet annealing on the hot-rolled steel strip for the non-oriented electrical steel sheet. A method for producing a non-oriented electrical steel sheet.