Technical field
[0001]The present invention is non-oriented electrical steel sheet, and a method for producing a non-oriented electrical steel sheet.
The present application, to 03 May 07, 2017, claiming priority based on Japanese Patent Application No. 2017-042547, filed in Japan, the contents of which are incorporated here.
BACKGROUND
[0002]Recently, motors for high-speed rotation (hereinafter, referred to high-speed rotation motor) is increasing. The high speed rotary motor, the centrifugal force acting on the rotary member such as a rotor is increased. Accordingly, the electrical steel sheet as the rotor material for high-speed rotation motor, a high strength is required.
[0003]
　Further, in the high-speed rotation motor, an eddy current is generated by the high frequency magnetic flux, motor efficiency decreases, and heat generation. The more calorific value, magnet in the rotor is demagnetized. Therefore, the rotor of the high-speed rotation motor, a low iron loss is obtained. Accordingly, the electrical steel sheet as the rotor material, not only high strength, is also determined excellent magnetic properties.
[0004]
　Solid solution strengthening, precipitation strengthening, by grain refinement or the like, the strength of the steel sheet increases. However, when the steel sheet with high strength These strengthening mechanism, there is a case that the magnetic properties are lowered. Therefore, it is not easy to achieve both high strength and excellent magnetic properties in the non-oriented electrical steel sheet.
[0005]
　Also, for non-oriented electrical steel sheet, there may be additional heat treatment is carried out. For example, when using the cut out blank for use as a stator core for a motor from a non-oriented electrical steel sheet, the center portion of the blank space is formed. With cut-out portion to form the space of the central portion as the rotor blank, i.e. from one non-oriented electrical steel sheet, be manufactured rotor blanks and blank stator core, because the yield increases ,preferable.
[0006]
　The rotor blank, as described above, is particularly required strength and low iron loss. On the other hand, high strength in the stator core blank although not required, is excellent magnetic properties (high magnetic flux density and low iron loss) is required. Therefore, when manufacturing a single non-directional rotor blanks and blank stator core from electrical steel sheet, after the blank which is cut out for the stator which is molded into the stator core, machining of the non-oriented electrical steel sheet which is high strength to increase the magnetic characteristics by removing the distortions caused by, it is necessary to sufficiently recrystallized by conducting additional heat treatment.
[0007]
　Therefore, in the non-oriented electrical steel sheet and blank the rotor blank for the stator core is manufactured, obtained high strength, and excellent magnetic properties before and after additional heat treatment.
[0008]
　In Patent Documents 1 to 7, the non-oriented electrical steel sheet is disclosed which achieve both excellent magnetic characteristics and high strength.
[0009]
　In Patent Document 1, Si: 3.5 ~ 7.0%, Ti: 0.05 ~ 3.0%, W: 0.05 ~ 8.0%, Mo: 0.05 ~ 3.0%, Mn : 0.1 ~ 11.5%, Ni: 0.1 ~ 20.0%, Co: 0.5 ~ 20.0%, and Al: one or two selected from among 0.5 to 18.0% the above species, the non-oriented electrical steel sheet is disclosed which contains in a range not exceeding 20.0%. In Patent Document 1, increasing the Si content, Ti, W, Mo, Mn, Ni, Co, by solid solution strengthening by Al, to enhance the strength of the steel sheet.
[0010]
　In Patent Document 2, Si: 3.5 contained ~ 7.0%, and, W: 0.05 ~ 9.0%, Mo: 0.05 ~ 9.0%, Ti: 0.05 ~ 10 .0%, Mn: 0.1 ~ 11.0%, Ni: 0.1 ~ 20.0%, Co: 0.5 ~ 20.0%, and, Al: from 0.5 to 13.0% After the hot-rolled sheet slab containing one or more selected from the group consisting of the hot rolling, to implement the cold rolled to a final thickness of 0.01 ~ 0.35 mm, then 800-1250 carried out annealing at a temperature range of ℃ and 0.01 ~ 5.0 mm average grain diameter, the method of producing a high tensile soft steel sheet is disclosed.
[0011]
　In Patent Document 3, C: 0.01% or less, Si: less than 2.0% or more 4.0%, Al: 2.0% or less, and P: contains 0.2% or less, and, Mn, Ni one or more of contained in a range of 0.3% ≦ Mn + Ni <10%, high-tensile electromagnetic steel sheets is disclosed the balance being Fe and inevitable impurity elements. In Patent Document 3, to enhance the strength of the steel sheet by solid solution strengthening by Mn and Ni.
[0012]
　In Patent Document 4, C: 0.04% or less, Si: less than 2.0% or more 4.0%, Al: 2.0% or less, and P: contains 0.2% or less, and, Mn, Ni one or more of contained in a range of 0.3% ≦ Mn + Ni <10%, and, Nb, and controls one or two of Zr, 0.1 <(Nb + Zr) / 8 (C + N ) and <1.0, high tensile electromagnetic steel sheets is disclosed the balance being Fe and inevitable impurity elements. Patent Document 4 enhances the strength of the steel sheet by solid solution strengthening by Mn and Ni, furthermore, Nb, by utilizing carbonitrides of Zr or the like, and achieve both high strength and magnetic properties.
[0013]
　In Patent Document 5, in mass%, C: 0.060% or less, Si: 0.2 ~ 3.5%, Mn: 0.05 ~ 3.0%, P: 0.30% or less, S: 0 .040% or less, Al: 2.50% or less, N: containing 0.020% or less, and a balance of Fe and unavoidable impurities, and high strength electrical steel sheet steel inside worked structure remains is disclosed ing.
[0014]
　In Patent Document 6, in mass%, C and N, C: 0.010% or less and N: 0.010% or less, and suppress the C + N ≦ 0.010%, Si: 1.5% or more 5. 0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less, S: 0.01% or less and Ti: 0.05% or more and 0.8% or less, contained such that the Ti / (C + N) ≧ 16, has a component composition of the balance Fe and unavoidable impurities, and existence ratio of non-recrystallized recovery structure in the steel sheet is in an area ratio of 50% or more higher strength non-oriented electrical steel sheet is disclosed.
[0015]
　In Patent Document 7, by mass%, C: 0.010% or less, Si: 3.5% more than 5.0% or less, Al: 0.5% or less, P: 0.20% or less, S: 0. 0.005% 002% or more or less, and N: include 0.010% or less, and the relationship in (5.94 × 10 of the S content (wt%) Mn -5 ) / (S%) ≦ Mn ≦ (4.47 × 10 -4 contained in) / range satisfying the (S%), the balance being component composition of Fe and unavoidable impurities, recrystallized grains in the steel sheet rolling direction cross-section (ND-RD sectional) area ratio of at least 30 to 90%, and non-oriented electrical steel sheet rolling direction length of the non-recrystallized grains group linked is a 1.5mm or less is disclosed.
[0016]
　As typified by Patent Documents 1 to 7 described above, high strength and excellent non-oriented electrical steel sheet for the purpose of both of the magnetic properties have been developed.
　However, the non-oriented electrical steel sheet disclosed in Patent Documents 1-7, is not considered characteristic after additional heat treatment. The present inventors have studied, when carrying out the additional heat treatment on the non-oriented electrical steel sheet disclosed in these documents, it was found that there may be a case that the magnetic properties are lowered.
[0017]
　Patent Document 8, in weight percent in the steel containing 7.00% or less of Si and 0.010% or less and C, from the surface of the stress relief annealing before the steel sheet having a thickness of 1/5 depth of the (100) in the mask plane parallel portion, (111) is the value of the ratio of the random texture of the X-ray reflection surface strength of orientation I (100) and I (111) and is, 0.50 ≦ I (100 ) / I (111) having a texture satisfying, magnetic flux density after stress relief annealing is non-oriented electrical steel sheet is disclosed high.
　However, not been studied at all for strengthening Patent Document 8. In Patent Document 8, loss of iron being evaluated W 15/50 is not intended to target high-speed rotation motor. In addition, W after the stress relief annealing 10/400 is unclear whether the high-frequency iron loss, such as excellent. In the high strength and aimed steel sheet and does not aim to high strength steel plate, different effects on the magnetic properties by heat treatment. Therefore, Patent Document 8 does not suggest an improvement in magnetic properties after heat treatment in the high-strength non-oriented electrical steel sheet.
[0018]
　As described above, conventionally, the non-oriented electrical steel sheet having excellent magnetic properties in the additional heat treatment before and after the high strength is not disclosed.
CITATION
Patent Document
[0019]
Patent Document 1: Japanese Sho 60-238421 Patent Publication
Patent Document 2: Japanese Sho 62-112723 Patent Publication
Patent Document 3: Japanese Patent Laid-Open 2-22442 discloses
Patent Document 4: Japanese Patent 2 -8346 JP
Patent Document 5: Japanese Patent 2005-113185 JP
Patent Document 6: Japanese Patent 2007-186790 JP
Patent Document 7: Japanese Patent 2010-090474 JP
Patent Document 8: Japanese Patent No. 8-134606 JP
Summary of the Invention
Problems that the Invention is to Solve
[0020]
　The present invention was made in view of the above problems. An object of the present invention has a high strength and non-oriented electrical steel sheet having excellent magnetic properties even after additional heat treatment, and is to provide a method of manufacturing the non-oriented electrical steel sheet.
Means for Solving the Problems
[0021]
　(1) non-oriented electrical steel sheet according to one embodiment of the present invention, the chemical composition, in mass%, C: 0.0100% or less, Si: 3.0% greater, 5.0% or less, Mn: 0 .1 ~ 3.0%, P: 0.20 % or less, S: 0.0018% or less, and, N: 0.0040% or less, Al: 0 ~ 0.9%, is selected from Sn and Sb 1 or more: 0 ~ 0.100%, Cr: 0 ~ 5.0%, Ni: 0 ~ 5.0%, Cu: 0 ~ 5.0%, Ca: 0 ~ 0.010%, and rare earth element (REM): 0 contains ~ 0.010%, the balance being Fe and impurities, wherein in a cross section parallel to the rolling surface of the non-oriented electrical steel sheet, the particle size is composed of crystal grains is 100μm or more that the crystal area of the tissue a is 1 to 30%, an average particle size of 25μm der following the crystal structure a non-crystalline structure a crystal structure B Ri, satisfy Vickers hardness HvB Togashiki (a) of the crystal structure B and Vickers hardness HvA of the crystal structure A.
HvA / HvB ≦ 1.000 (a)
[0022]
(2) The non-oriented electrical steel sheet according to (1), the chemical composition, Al: 0.0001 ~ 0.9%, 1 or more selected from Sn and Sb: 0.005 ~ 0.100 %, Cr: 0.5 ~ 5.0%, Ni: 0.05 ~ 5.0%, Cu: 0.5 ~ 5.0%, Ca: 0.0010 ~ 0.0100%, and rare earth elements (REM): 0.0020 may contain one or more selected-from the group consisting of 0.0100% or less.
[0023]
(3) The method of producing non-oriented electrical steel sheet according to another aspect of the present invention is a method for producing a non-oriented electrical steel sheet according to (1), having the chemical composition according to (1) after the slab was heated at 1000 ~ 1200 ° C., the step of producing a hot rolled steel sheet by carrying out hot rolling, to the hot-rolled steel sheet, the average heating rate at 750 ~ 850 ℃ 50 ℃ / sec and then, the step of performing a hot-rolled sheet annealing to the maximum temperature and 900 ~ 1150 ° C., the cold rolling or warm rolling at a reduction rate of 83% or more with respect to the hot-rolled steel sheet after the hot rolled sheet annealing implementation and process for producing the intermediate steel plate was performed with respect to the intermediate steel plate, the maximum temperature 700 ~ 800 ° C., the finish annealing for the average cooling rate in the temperature range of 700 ~ 500 ° C. and 50 ° C. / sec or higher comprising the steps of, a.
The invention's effect
[0024]
　According to this aspect of the present invention have high strength, and non-oriented electrical steel sheet and a manufacturing method thereof excellent magnetic characteristics can be obtained even after additional heat treatment.
DESCRIPTION OF THE INVENTION
[0025]
　The present inventors have found that in order to solve the above problems, investigated the strength and magnetic properties of high-strength non-oriented electrical steel sheet.
[0026]
　Initially, in mass%, C: 0.0012%, Si : 3.3%, Mn: 0.4%, Al: 0.3%, P: 0.02%, N: containing 0.0016% and, further, S: a slab containing 0.0021%, C, Si, Mn , Al, P, N content is as defined above, and, S: a slab containing 0.0011% We were prepared two slabs. After heating the two slabs at 1150 ° C., and carrying out the hot rolling to produce a hot rolled steel plate having a plate thickness of the 2.0 mm. For these hot-rolled steel sheet was performed hot rolled sheet annealing. Maximum temperature of hot-rolled sheet annealing is 1050 ° C., an average heating rate in the temperature range of 750 ~ 850 ° C., and the following two.
　Heating rate condition 1: 30 ° C. / sec,
　the heating rate condition 2: 60 ° C. / sec
[0027]
　It was performed pickling against hot-rolled steel sheet after hot rolled sheet annealing. Then conducted to cold rolling with respect to hot-rolled steel sheet to produce a cold-rolled steel plate having a plate thickness of the 0.35 mm. By carrying out finish annealing at a maximum attained temperature of 770 ° C. relative to the cold-rolled steel sheet, to produce a non-oriented electrical steel sheet. At this time, the average cooling rate at 700 ~ 500 ° C. after the finish annealing, and the following two.
　Cooling rate condition 1: 30 ° C. / sec
　cooling rate condition 2: 60 ° C. / sec
[0028]
　Assuming rotor blank was measured tensile relative to the non-oriented electrical steel sheet prepared strength and magnetic properties (magnetic flux density and iron loss).
　Furthermore, assuming a stator core blank, samples were taken from the non-oriented electrical steel sheet, in a nitrogen atmosphere to conduct additional heat treatment for two hours at 800 ° C., the sample of tissue was sufficiently grain growth crystal was the organization. Enough for the sample having a particle grown crystal structure, magnetic characteristics were measured (magnetic flux density and iron loss).
[0029]
　As a result of the measurement, any S content, and any conditions (heating rate condition 1, the heating rate condition 2, the cooling rate condition 1, the cooling rate condition 2) also in the non-oriented electrical steel sheet has a tensile strength of 600MPa or more, it was high strength as compared with conventional non-oriented electrical steel sheet (for example steel sheets that are commonly applied to 50A230 of JISC2550). The magnetic properties were comparable to conventional non-oriented electrical steel sheet.
　Thus, non-oriented electrical steel sheet produced by any of the conditions also had the properties suitable for the rotor blank.
[0030]
　On the other hand, in the magnetic properties after additional heat treatment, low S content, accelerate the heating rate in the hot-rolled sheet annealing (heating rate condition 2: 60 ° C. / sec), and was accelerated cooling rate in final annealing (cooling speed condition 2: 60 ° C. / sec) was the highest in the non-oriented electrical steel sheet. In contrast, a high S content, the heating rate is slow (heating rate condition 1: 30 ° C. / sec), or the cooling rate is slow in the finishing annealing (cooling rate condition 1: 30 ° C. / sec) oriented electrical the steel sheet, magnetic properties after additional heat treatment, in particular the magnetic flux density was lowered.
　In other words, a low S content, heating rate in the hot-rolled sheet annealing, and, only when the cooling rate after finish annealing is faster, it had either Suitable also characteristic of the rotor for blank and blank stator core.
[0031]
　The present inventors have found that in a cross section perpendicular to the rolling direction of the 1/4 thickness section (steel plate parallel to the rolling surface of the non-oriented electrical steel sheet before additional heat treatment produced in each condition, from the rolled surface of plate thickness 1 / 4 embedded depth position (the thickness of the non-oriented electrical steel sheet t (cross section unit including the position of t / 4 when a mm))), polished and subjected to structure observation. As a result, in each of the non-oriented electrical steel sheet, microstructure, and the crystal structure A is a particle size of more than 100μm grain area, the particle size of each crystal grain is less than 100μm average particle size of 25μm was mixed structure consisting of at which the crystal structure B below.
[0032]
　As described above, the non-oriented electrical steel sheet produced by any of the conditions are also differences in the optical microscope level organization was small. Therefore, for these non-oriented electrical steel sheet it is considered to strength and magnetic characteristics before additional heat treatment was almost equal.
[0033]
　On the other hand, as described above, if you add heat treated non-oriented electrical steel sheet produced by the respective conditions, clear difference occurs in the magnetic flux density after additional heat treatment. This is a result of tissue included in the crystal structure A before additional heat treatment was grain growth by heat treatment, is considered to crystal orientation in each of the non-oriented electrical steel sheet which is the material change due to the a different state. That is, the S content and production conditions, is considered that the difference in crystal orientation that develop during additional heat treatment occurs. The present inventors have found that the reason a difference in crystal orientation that develop during additional heat treatment occurs, was considered to be the difference in the microstructure of the crystal structure A it could not be determined under an optical microscope level (dislocation structure).
[0034]
　Accordingly, the present inventors, the non-oriented electrical steel sheet produced by the respective conditions, were observed with an electron microscope and X-ray. As a result, a low S content, and accelerate the heating rate in the hot-rolled sheet annealing (60 ° C. / sec), the cooling rate quickened (60 ° C. / sec) non-oriented electrical steel sheet in the finish annealing, the crystal structure an area ratio of 1 to 30% of a, and Vickers hardness HvA crystal structure a is was equal to or less than the Vickers hardness HvB crystal structure B. In contrast, in the non-oriented electrical steel sheet produced by other conditions, both, Vickers hardness HvA crystal structure A has a value greater than the Vickers hardness HvB crystal structure B.
[0035]
　Based on the above results, the present inventors have found that the hardness ratio HVA / HVB is thought to affect the magnetic properties improve by subsequent additional heat treatment. Therefore, further subjected to study, adequate strength is obtained at the previous additional heat treatment, it was identified tissue obtained has excellent magnetic properties when allowed to proceed the grain growth by additional heat treatment.
[0036]
　The non-oriented electrical steel sheet of the present invention has been completed based on the above findings, the chemical composition, in mass%, C: 0.0100% or less, Si: 3.0% greater, 5.0% or less, Mn: 0.1 ~ 3.0%, P: 0.20 % or less, S: 0.0018% or less, and, N: containing 0.0040% or less, if necessary, Al: 0.9% or less , one or more selected from Sn and Sb: 0.100% or less, Cr: 5.0% or less, Ni: 5.0% or less, and, Cu: 5.0% or less, Ca: 0.010% hereinafter, and rare earth elements (REM): contains at least one member selected from the group consisting of 0.010% or less, the balance being Fe and impurities, in a cross section parallel to the rolling surface of the non-oriented electrical steel sheet , the area ratio of crystal structure a constructed in which the crystal grain particle diameter 100μm or more is 1% to 30% crystalline The average particle diameter of the woven crystal structure B is a crystal structure other than A is at 25μm or less, satisfying the Vickers hardness HvB Togashiki (1) of the Vickers hardness HvA crystal structure A and the crystal structure B.
HvA / HvB ≦ 1.000 (1)
[0037]
　A method of manufacturing a non-oriented electrical steel sheet of the present invention, after the slab having the above chemical composition is heated at 1000 ~ 1200 ° C., the step of producing a hot rolled steel sheet by carrying out hot rolling, hot-rolled steel sheet respect, the average heating rate at 750 ~ 850 ° C. and 50 ° C. / sec or more, a step of performing a hot-rolled sheet annealing to the maximum temperature and 900 ~ 1150 ° C., hot rolled steel sheet after hot rolled sheet annealing a step of producing the intermediate steel plate by carrying out the cold rolling or warm rolling at a reduction rate of 83% or more with respect to, the intermediate steel plate, 700 ~ 800 ° C. the highest temperature, the temperature range of 700 ~ 500 ° C. and a final annealing step to an average cooling rate of 50 ° C. / sec or more at.
[0038]
　It will be described in detail a method for manufacturing the non-oriented electrical steel sheet according to an embodiment (non-oriented electrical steel sheet according to the present embodiment) non-oriented electrical steel sheet according to the embodiment and the embodiment of the present invention.
[0039]
　[Non-oriented electrical steel sheet]
　The chemical composition of non-oriented electrical steel sheet according to the present embodiment contains the following elements. Below,% related to elements means "% by weight".
[0040]
　C: 0.0100% or less
　carbon (C) has the effect of increasing the strength by precipitation of carbides. However, in the non-oriented electrical steel sheet according to the present embodiment, the high strength is primarily a solid solution strengthening of substitutional elements such as Si, it is achieved by the control of the ratio of the crystal structure A and the crystal structure B. Therefore, C for high strength may not be contained. That is, the lower limit of the C content including 0%. However, C the lower limit so is usually contained in unavoidable or 0 percent.
　On the other hand, if the C content is too high, the magnetic properties of non-oriented electrical steel sheet is lowered. Also, the processability of the non-oriented electrical steel sheet is reduced according to the present embodiment is a high Si steel. Therefore, C content is 0.0100% or less. C content is preferably at 0.0050% or less, still more preferably 0.0030% or less.
[0041]
　Si: 3.0% greater, 5.0% or less
　Silicon (Si) has the effect of deoxidizing the steel. Further, Si is to increase the electrical resistance of the steel, to reduce iron loss of non-oriented electrical steel sheet (improvement). Si further, Mn contained in the non-oriented electrical steel sheet, Al, as compared to other solid solution strengthening elements such as Ni, having a high solid solution strengthening ability. Therefore, Si is most effective for achieving a good balance of high strength and low iron loss. If Si content is 3.0% or less, not the effect. Therefore, the content of Si 3.0% greater.
　On the other hand, if the Si content is too high, productivity, particularly, bending workability hot-rolled steel sheet is reduced. As described later, by properly controlling the particle size of the hot-rolled steel sheet, the bending decrease in workability can be suppressed. However, Si content if it exceeds 5.0%, cold workability is deteriorated. Therefore, Si content is 5.0% or less. Preferably, Si content is less 4.5%.
[0042]
　Mn: 0.1 ~ 3.0%
　manganese (Mn) increases the electrical resistance of the steel, to reduce iron loss. If Mn content is less than 0.1%, not the effect. Further, Mn content is less than 0.1%, Mn sulfide is produced finely. Fine Mn sulfide, or inhibit movement of the domain walls, or to inhibit the grain growth during the manufacturing process. In this case, the magnetic flux density decreases. Therefore, the Mn content is 0.1% or more. Preferably, 0.15% or more, more preferably 0.4% or more.
　On the other hand, Mn content if it exceeds 3.0%, it austenite transformation is likely to occur, the magnetic flux density decreases. Therefore, Mn content is 3.0% or less. Preferably not more than 2.5%, more preferably 2.0% or less.
[0043]
　P: 0.20% or less
　phosphorus (P) increases the strength of steel by solid solution strengthening. However, steel is embrittled P is segregated if the P content is too high. Accordingly, P content is 0.20% or less. P content is preferably not more than 0.10%, more preferably not more than 0.07%.
[0044]
　S: 0.0018% or less
　of sulfur (S) is an impurity. S forms sulfides such as MnS. Sulfides, hinder domain wall motion, further, to inhibit grain growth, thereby lowering the magnetic properties. Thus, S content is preferably as small as possible. In particular, when the S content exceeds 0.0018%, the magnetic properties are significantly reduced. Thus, S content is less 0.0018%. Preferably not more than 0.0013%, more preferably at most 0.0008%.
　On the other hand, a Mn content and S content, the manufacturing conditions described later, by appropriately controlling the generation of MnS, S is the effective crystal structure A in order to avoid deterioration of the magnetic properties after the additional heat treatment It is also the element contributing to the formation of dislocations structure in. To obtain this effect, S content is preferably 0.0001% or more.
[0045]
　N: 0.0040% or less
　nitrogen (N) is an impurity. N reduces the magnetic properties after additional heat treatment. Therefore, N content is 0.0040%. N content is preferably 0.0020% or less.
[0046]
　The chemical composition of the non-oriented electrical steel sheet according to the present embodiment, a basic and the elements described above, that it consists of Fe and impurities the balance. However, if desired, instead of a part of Fe, to the extent that the following further contain optional elements (Al, Sn, Sb, Cr , Ni, Cu, Ca, and / or REM) 1 or more it may be. These optional elements, since it is not always necessary to contain, the lower limit is 0%.
　The impurities, in producing the non-oriented electrical steel sheet industrially, ore as a raw material, there is to be mixed etc. from scrap or manufacturing environment, the non-oriented electrical steel sheet according to the present embodiment It means what is allowed in a range that does not adversely affect.
[0047]
　[For any
　element] Al: 0 ~ 0.9%
　of aluminum (Al) is an optional element and may not be contained. Al as well as Si, has the effect of deoxidizing the steel. Al further enhance the electrical resistance of the steel, to reduce iron loss. To obtain these effects, the Al content is preferably made 0.0001% or more.
　However, as compared to Si, Al is not contribute to strengthening of the steel. Furthermore, if the Al content is too high, workability is lowered. Therefore, even if to be contained, Al content is 0.9% or less. Preferably not more than 0.7%.
[0048]
　Least one selected from the group consisting of Sn and Sb: 0 ~ 0.100%
　none tin (Sn) and antimony (Sb) is an optional element and may not be contained. Sn and Sb, to improve the texture of the non-oriented electrical steel sheet (for example, by increasing the grain contributes orientation magnetic properties improve) enhance the magnetic properties. If obtained enabled the effect stably, one or more of the total content is selected from the group consisting of Sn and Sb is preferably set to 0.005% or more.
　However, the total content of these elements if it exceeds 0.100% steel becomes brittle. In this case, or broken steel sheet during manufacture, scab is or generated. Therefore, even if to be contained, one or more of the total content is selected from the group consisting of Sn and Sb is 0.100% or less.
[0049]
　Cr: 0 ~ 5.0%
　chromium (Cr) is an optional element and may not be contained. Cr increases the electrical resistance of the steel. In particular, if it is contained in Cr with Si, Si, the electrical resistance of the steel than when contained alone Cr respectively increased, thereby reducing iron loss. Cr further enhance the productivity of the high Si steels such as non-oriented electrical steel sheet according to the present embodiment, the corrosion resistance enhancing. If obtained enabled the effects stably, the Cr content is preferably 0.5% or more.
　However, Cr content if it exceeds 5.0%, the cost increases to saturation effect. Therefore, even if to be contained, Cr content is 5.0% or less. Cr content is preferably 1.0% or less.
[0050]
　Ni: 0 ~ 5.0%
　nickel (Ni), without lowering the saturation magnetic flux density, steel strengthening solid solution, further reducing the iron loss by increasing electrical resistance of the steel. If obtained enabled the effects stably, the Ni content is preferably 0.05% or more.
　However, Ni content if it exceeds 5.0%, the higher the cost. Therefore, even if to be contained, Ni content is 5.0% or less. Ni content is preferably 2.0% or less.
[0051]
　Cu: 0 ~ 5.0%
　copper (Cu) increases the strength of steel by solid solution strengthening. Cu further by carrying out the aging treatment at a temperature of about 500 ° C., to produce a fine Cu precipitation phase, to strengthen the steel. If obtained enabled the effects stably, the Cu content is preferably 0.5% or more.
　However, Cu content if it exceeds 5.0%, the steel becomes brittle. Therefore, even if to be contained, Cu content is 5.0% or less. Cu content is preferably 2.0% or less.
[0052]
　Ca: 0 ~ 0.010%
　rare earth elements (REM): 0 ~ 0.010%
　of calcium (Ca) and REM fixes the S combines with S in steel. This increases the magnetic properties of the steel. If it obtained enabled the effect stable, Ca content of 0.001% or more, or, the REM content is preferably 0.002% or more.
　On the other hand, if the Ca content and the REM content exceeds 0.010%, respectively, the effect is saturated and the cost becomes high. Therefore, even if to be contained, Ca content is 0.010% or less, REM content is 0.010% or less.
[0053]
　REM in the present embodiment, Sc, Y, and means lanthanoid (atomic number 57 No. La ~ 71 No. Lu), REM content means the total content of these elements.
[0054]
　[Microstructure in a cross section parallel to the rolling surface of the non-oriented electrical steel sheet]
　of the above non-oriented electrical steel sheet, in a cross section parallel to the rolling surface of the 1/4 depth position of the sheet thickness from the rolled surface, microstructure , and a crystal structure a and the crystal structure B.
[0055]
　In the present embodiment, the crystal structure A, the crystal grain size of a region made up of more crystal grains 100 [mu] m. On the other hand, the crystal structure B, the crystal grain size is a region composed of less than 100μm grain.
[0056]
　Crystal structure A is an area which disappears is encroachment by additional heat treatment which performs a gradual heating. In a cross section parallel to the rolling surface, if out of range area ratio is 1 to 30% of the crystal structure A, it is difficult to avoid the deterioration of the magnetic properties when obtained by particle growth in additional heat treatment. It will be described in detail later mechanism. Further, if the area ratio of crystal structure A is less than 1%, the crystal structure B is the strength of coarse-grained likely non-oriented electrical steel sheet is lowered. Further, when the area ratio of crystal structure A exceeds 30%, the magnetic properties when obtained by particle growth in additional heat treatment is lowered (deteriorated). Therefore, the area ratio of crystal structure A is 1 to 30%. A preferable lower limit of the area ratio of crystal structure A is 5%, and the preferable upper limit is 20%.
[0057]
　In a cross section parallel to the rolling surface, when the area ratio of crystal structure A 1 to 30% area ratio of the crystal structure B is 70 to 99%. Therefore, the mechanical properties of non-oriented electrical steel sheet according to the present embodiment is mainly determined by the crystal structure B.
　The crystal structure B is an area for grain growth by adding a heat treatment for performing slow heating.
　If the average particle size of the crystal structure B is greater than 25 [mu] m, the magnetic characteristics before additional heat treatment is improved, it becomes difficult to satisfy the strength properties. Further, although the details will be described later mechanism, the average particle diameter of the crystal structure B is greater than 25 [mu] m, the magnetic properties when obtained by particle growth in additional heat treatment is greatly reduced.
　Thus, in a cross section parallel to the rolling direction, an average particle diameter of the crystal structure B is required to be 25μm or less. Preferred upper limit of the average grain size of crystal structure B is 20 [mu] m, more preferably from 15 [mu] m.
[0058]
　In this embodiment, the 1/4 depth position of the sheet thickness from the rolling surface, in a cross section parallel to the rolling plane, it is sufficient that the tissue as described above. This tissue 1/4 depth position of the sheet thickness from the rolling surface, a typical organization of the steel sheet, because a large influence on the properties of the steel sheet.
[0059]
　[Measurement method for average particle diameter of the area ratio of crystal structure A and the crystal structure B]
　an average particle diameter of the area ratio and crystal structure B crystal structure A can be measured by the following method.
[0060]
　1/4 depth position of the sheet thickness from the rolling surface of the non-oriented electrical steel sheet is prepared by grinding or the like samples having cross sections parallel to the rolling surface. The polished surface of the sample (hereinafter, referred to as the observation plane) with respect to, after adjusting the surface by the electrolytic polishing, implementing the crystal structure analysis using electron backscatter diffraction method (EBSD).
[0061]
　The EBSD analysis, among the viewing surface, the boundary of the crystal orientation difference is 15 ° or more and the crystal grain boundary, the individual regions surrounded by the grain boundaries and the crystal grain includes grain 10000 or more observing region (observation region). In observation region, it defines the diameter at the time of the crystal grains and the area of ​​a circle equivalent to (equivalent circle diameter) and particle size. In other words, the particle size refers to the circle equivalent diameter.
[0062]
　Particle size region includes crystal grains is 100μm or more is defined as a crystal structure A, obtain the area ratio. The diameter is defined region includes crystal grains is less than 100μm (i.e. tissue other than the crystal structure A) and the crystal structure B, obtain the average crystal grain size. These measurements can be relatively easily carried out by image analysis.
[0063]
　[Crystal structure Hardness A and crystal structure B]
　Further, in the non-oriented electrical steel sheet according to the present embodiment, the hardness of the crystal structure A and the crystal structure B satisfies the equation (1).
　HvA / HvB ≦ 1.000
　(1) When the HvA / HvB> 1.000, the magnetic properties after additional heat treatment is lowered.
　Here, "HvA" is the crystal structure A, a Vickers hardness of a test force (load) 50 g, "HvB" is a Vickers hardness of at the crystal structure B, test force (load) 50 g. Vickers hardness is measured according to JIS Z 2244 (2009).
[0064]
　More specifically, the Vickers hardness at least 20 points in the area of ​​the crystal structure A was measured by the above method, the average value is defined as the Vickers hardness HvA crystal structure A. Similarly, the Vickers hardness at least 20 points in the area of ​​the crystal structure B is measured by the method described above, the average value is defined as the Vickers hardness HvB crystal structure B.
[0065]
　On the other hand, since it is difficult to the HVA / HVB less than 0.900, the HVA / HVB may be 0.900 or more. The lower limit of HVA / HVB may be 0.950, or 0.970 or more.
[0066]
　[Standard specifies the microstructure]
　In non-oriented electrical steel sheet according to the present embodiment, as described above, the 1/4 depth position of the sheet thickness from the rolled surface, the microstructure of a cross section parallel to the rolling surface " crystal structure a "," crystal structure B ", further" the ratio of the hardness of their crystal structure "is controlled to a predetermined range. These features will be described below. In the following description, also it has part of the unexplained in detail, in the mechanism, previously refused part is estimated.
[0067]
　"Crystal structure A" in the present embodiment, the optical microscope observation, the region is not generally encroachment in "recrystallized grains", i.e., no significant difference between the "non-recrystallized structure." However, the crystal structure A is fully recovered by the finish annealing, it has become very soft. For this reason, different from the general "non-recrystallized structure". Further, as assessed by the amount of accumulated strain (e.g. IQ value) by EBSD, rather than non-recrystallized structure, close to the recrystallization structure.
　Accordingly, in the present embodiment, "the crystal structure A" distinction to be defined from a typical non-recrystallized structure.
[0068]
　"Crystal structure B" in the present embodiment, the matrix by nucleation from a processed structure is a region similar to the orientation difference grew to produce large crystal "recrystallization texture." However, the crystal structure B in the present embodiment, areas not encroachment on the recrystallized grains are also included. Therefore, "crystal structure B" in this embodiment is defined separately from the simple "recrystallized structure".
[0069]
　Non-oriented electrical steel sheet according to the present embodiment, the hardness of the "crystal structure A" is less than the hardness of the "crystal structure B" (that is, satisfies the equation (1)) is characterized by.
[0070]
　Also, the non-oriented electrical steel sheet according to the present embodiment is characterized in the particle size distribution. As is apparent when considering the provisions described above, except the crystal structure A includes crystal grains of 100μm or more particle size present up to 30 percent, the average grain size of crystal structure B is very small and 25μm or less. This means that in microstructure, which means that the crystal grains of intermediate size of about 30 ~ 90 [mu] m there is little. That is, in the non-oriented electrical steel sheet according to the present embodiment, the grain size distribution is the so-called mixed grain.
　General, for example, if the particle size distribution normal distribution, in the crystal structure such to achieve grain growth so that there is a particle size of 100 [mu] m, the number 10μm grain also relatively abundant, average particle diameter is about 50μm.
[0071]
　The crystal structure A and the crystal structure B are mixed at a predetermined ratio, and the hardness ratio HVA / HVB satisfies Equation (1), in non-oriented electrical steel sheet according to the present embodiment, without performing additional heat treatment when utilizing (when assuming use as a rotor blank), having excellent strength and magnetic properties. On the other hand, (if assuming use as blank stator core) When using by conducting additional heat treatment, upon grain growth by adding a heat treatment, along with the iron loss is improved, lowering the magnetic flux density is suppressed.
[0072]
　[For formula (2)]
　in the non-oriented electrical steel sheet described above, it defines a magnetic flux density of the non-oriented electrical steel sheet before carrying out the additional heat treatment and BA (T). Furthermore, 100 ° C. / time heating rate, 800 ° C. The highest temperature, and after the additional heat treatment was carried out for 2 hours holding time at 800 ° C., the magnetic flux density of the non-oriented electrical steel sheet BB (T) It is defined as. At this time, in the non-oriented electrical steel sheet according to the present embodiment, the magnetic flux density BA and BB satisfies the following equation (2).
　BB / BA ≧ 0.980 (2)
[0073]
　BB / BA is preferably 0.985 or more, and more preferably 0.990 or more. The upper limit of the BB / BA is not particularly limited, there is no characteristic degradation by the addition heat treatment (i.e., BB / BA = 1.000) It is also a reference to a target. However, the addition heat treatment, preferably the orientation grow preferentially for magnetic properties, as a result, there is a case where BB / BA exceeds 1.000. However, even in this case, BB / BA that is little more than 1.015.
[0074]
　Heating rate as described above, the maximum temperature and the retention time is an example of the additional heat treatment conditions. This condition is used the values ​​considered representative as the conditions of the stress relief annealing which is at present practically implemented. However, in the non-oriented electrical steel sheet according to the present embodiment, the effect of suppressing the decrease in magnetic flux density due to additional heat treatment, the heating rate, maximum temperature and the holding time is not limited to this value, some wide range it can also be confirmed by the inner. For example, 30 ~ 500 ° C. / time heating rate, the maximum temperature 750 ~ 850 ° C., in a range of the holding time at 750 ° C. or higher 0.5 to 100 hours, the effect is obtained.
[0075]
　Additional heat treatment, generally, if you a high temperature for a long time of heat treatment is compared with the finish annealing to grain growth, by heating at a low speed, thereby grain growth relatively low temperature and at a long-time heat treatment.
[0076]
　General finishing annealing, because it is carried out at 10 ℃ / s (36000 ℃ / hour) of about heating rate, the upper limit of the additional heat treatment the heating rate, can present temperature of this degree. However, considering the stress relief annealing of the common core, heating at such a high speed is difficult. Further, when the heating rate is too fast, it is also feared that the heating is uneven. Therefore, the heating rate of the additional heat treatment, for example, is 500 ° C. / hour or less.
[0077]
　On the other hand, too slow heating rate, particle growth behavior peculiar is hardly expressed in the non-oriented electrical steel sheet according to the present embodiment as described below. Therefore, the lower limit of the heating rate of the additional heat treatment is 30 ° C. / hour.
[0078]
　The maximum temperature and the holding time, taking into account the general stress relief annealing condition, the maximum temperature is 750 ~ 850 ° C., and 750 ° C. The holding time at least is 0.5 to 100 hours.
[0079]
　In the present embodiment, the crystal structure A and the ratio of the crystal structure B, the average particle diameter of the crystal structure B, by controlling the hardness ratio of the crystal structure A and the crystal structure B, when allowed to grain growth an additional heat treatment the reason why can be of suppressing a decrease in magnetic properties is not necessarily clear and is presumed as follows.
[0080]
　Non-oriented electrical steel sheet, which is the target of the present embodiment, inclusions in the steel nitrogen to form a (deposit) (N) content and carbon (C) content is reduced to very low levels . Precipitates are formed in such steel, the particle size becomes as following fine 1.0 .mu.m, 0.2 [mu] m are also many forms following precipitates. Such fine precipitates, for example, a particle size less fine precipitates 0.2μm affects the magnetic properties and the like.
[0081]
　If there are fine precipitates in the steel, dislocations are pinned hardly lost by precipitation, region dislocations integrated around the precipitate tends to be (high dislocation density region) is formed (remaining easy to become).
[0082]
　From generally precipitate high dislocation density regions surrounding, by recrystallization, it is said that crystals having a random orientation is easily formed. However, the non-oriented electrical steel sheet according to the present embodiment, as described later, mild heat treatment on the intermediate steel sheet after cold rolling or warm rolling (finish annealing) is performed, the steel sheet after finish annealing crystal structure A is left in. If there is precipitate in such crystal structure A, when was subsequently proceed recrystallized by conducting additional heat treatment at Xu heating, undesirable crystal orientations for magnetic properties of non-oriented electrical steel sheet development is promoted.
[0083]
　In contrast, if the recrystallization proceeds by adding heat treatment at Xu heating, dislocation structure in the crystal structure A before adding the heat treatment (recovery tissue) is formed of a high dislocation density region is suppressed due like precipitate and, if the homogeneous cell structure (or mesh of two-dimensional structure), preferably the orientation is developed for the magnetic flux density in a subsequent additional heat treatment, a relatively high magnetic flux density is considered to be obtained.
[0084]
　If dislocation structure of the crystal structure A is a homogeneous cell structure, the ratio of the Vickers hardness HVA crystal structure A, and the Vickers hardness HVB crystal structure B (HVA / HVB) satisfies the equation (1). That is, the crystal structure A dislocation structure forms a homogeneous cell structure or a simple two-dimensional structure becomes softer ones from non-recrystallized structure obtained by forming a complex high dislocation density region around the precipitates. In this case, after the additional heat treatment, deterioration of the magnetic characteristics can be suppressed.
　Therefore, in the non-oriented electrical steel sheet according to the present embodiment, as an index indicating that the dislocation structure of the crystal structure A is a homogeneous cell structure, defines a formula (1).
[0085]
　[Production Method]
　method of manufacturing the non-oriented electrical steel sheet will be described. Manufacturing method described below is one example of a method for producing a non-oriented electrical steel sheet according to the present embodiment. Therefore, the non-oriented electrical steel sheet according to the present embodiment may be manufactured by methods other than the production method described below.
[0086]
　Method for producing a non-oriented electrical steel sheet according to the present embodiment includes a step of manufacturing a hot rolled steel sheet slabs by hot rolling (hot rolling process), annealing against hot-rolled steel sheet (hot-rolled sheet annealing) carrying out the process (hot-rolled sheet annealing step), a step of producing the intermediate steel plate by carrying out the cold rolling or warm rolling with respect to hot-rolled steel sheet after hot rolled sheet annealing (cold rolling process or warm It comprises a rolling step), a step of performing a final annealing for the intermediate steel plate (finish annealing step). Hereinafter, the respective steps will be described.
[0087]
　[Hot Rolling Step]
　In the hot rolling process, to produce a hot-rolled steel sheet slabs by hot rolling.
[0088]
　Slabs are prepared in a known manner. For example, to produce the molten steel in a converter furnace or electric furnace or the like. And secondary refining by degassing facilities relative produced molten steel, the molten steel having the above chemical composition. Casting slab by continuous casting or ingot casting method using the molten steel. The cast slab may be slabbing.
[0089]
　Against the slab that has been prepared by the above process, carrying out the hot rolling. Preferred heating temperature of the slab in the hot rolling process is 1000 ~ 1200 ° C.. If it exceeds 1200 ° C. The heating temperature of the slab, in the hot rolling before the slab, the crystal grains become coarse. As the chemical composition of non-oriented electrical steel sheet according to the present embodiment, the tissue of the Si content is high steel sheet is ferrite single phase from the stage of the slab. In the heat history in the hot rolling process, the tissue is not transformed. Therefore, if the heating temperature of the slab is too high, the crystal grains are easily coarsened, hot coarse worked structure after rolling (flat structure) tends to remain. Coarse flat organization hardly lost by recrystallization in hot-rolled sheet annealing step which is the next step in the hot rolling process. In the hot-rolled sheet annealing tissue, the coarse flat tissue remains, even those subsequent steps is preferred, tissue can not be obtained which is required in the non-oriented electrical steel sheet according to the present embodiment. Therefore, the upper limit of the heating temperature of the slab is 1200 ° C..
　On the other hand, if the heating temperature of the slab is too low, the processability of the slab is lowered, the productivity of a typical hot rolling equipment is reduced. Therefore, the lower limit of the heating temperature of the slab is 1000 ° C..
　The preferable upper limit of the slab heating temperature is 1180 ° C., more preferably 1160 ° C.. A preferred lower limit of the slab heating temperature is 1050 ° C., more preferably 1100 ° C..
　The hot rolling conditions may be carried out under known conditions.
[0090]
　[Hot-rolled sheet annealing step]
　In the hot-rolled sheet annealing step, with respect to hot-rolled steel sheet produced by hot rolling process, carried annealing (hot-rolled sheet annealing). Thus, in the structure of the hot-rolled steel sheet after hot rolled sheet annealing, a recrystallization ratio is 95% or more, average particle diameter of recrystallized grains to 50μm greater. Or a recrystallization ratio is less than 95%, the average particle size of the recrystallized grains is 50μm or less, it is assumed that the product of the crystal structure was integrated into {111}, the magnetic characteristic is inferior.
[0091]
　The structure of the hot-rolled steel sheet after hot rolled sheet annealing to be as described above, in the hot-rolled sheet annealing step, of heating conditions, the average heating rate HR between 750 ~ 850 ° C. 750-850 , and the highest the reaching temperature Tmax be as follows.
[0092]
　750 average heating rate HR between ~ 850 ° C. 750-850 : 50 ° C. / sec or more
　in the heating of the hot-rolled steel sheet in the hot-rolled sheet annealing, the average heating rate HR in the range of 750 ~ 850 ° C. 750-850 50 ℃ / a second or more. The average heating rate HR 750-850 if the the rapid heating above 50 ° C. / sec, while maintaining a high dislocation density of the flat tissue after hot rolling, it is possible to start the recrystallization and grain growth. In this case, it is possible to easily eliminate the flat tissue. Further, while maintaining such high dislocation density, recrystallization is initiated, then grain growth tissue, subsequently performed, cold rolling or warm rolling step, and the finish annealing step, according to the present embodiment the tissue being required in the non-oriented electrical steel sheet.
[0093]
　The average heating rate HR 750-850 if they are too late is, flat organization, or forward recovery before recrystallization start, the so-called "in-situ recrystallization" re crystal ends up or completed. In this case, the observation of an optical microscope level, the difference between those carried out rapid heating is not clear. However, the crystal grains formed by recovery and in-situ recrystallization, the crystal grains formed by recrystallization is a difference in crystal orientation. Therefore, the average heating rate HR 750-850 if they are too slow are tissue after cold rolled steel sheet and the recrystallization annealing is not a tissue required for non-oriented electrical steel sheet according to the present embodiment. It is not necessary to limit the upper limit of the heating rate, the upper limit of the equipment capacity, the substantial upper limit of the heating rate.
[0094]
　Flat tissue even though recrystallized at a later point in time the hot rolled sheet annealing, because it is formed without passing through the transformation, tends strong accumulation in special orientation as a crystal orientation. Therefore, flat organization then preferably cold rolling or warm rolling process, even after the finish annealing step, causes the magnetic characteristics are deteriorated when obtained by particle growth with additional heat treatment at Xu heating.
[0095]
　The average heating rate HR 750-850 preferable lower limit of the temperature range to apply is 600 ° C., more preferably 450 ° C. to tissue recovery begins. The average heating rate HR 750-850 preferable upper limit of the temperature range to apply is 900 ° C., more preferably 950 ° C.. That is, most preferably set to 50 ° C. / sec or more average heating rate between 450 ~ 950 ° C..
[0096]
　The maximum temperature Tmax: 900 ~ 1150 ° C.
　to 900 ~ 1150 ° C. The maximum temperature Tmax in the hot rolled sheet annealing. The maximum temperature Tmax is low too if more than 95% of the recrystallized structure can not be obtained, magnetic properties of the final product is deteriorated. On the other hand, if the maximum temperature Tmax is too high, recrystallized grain structure is easily broken cracked at step after becomes coarse, the yield is significantly reduced.
[0097]
　Heat treatment time of the hot rolled sheet annealing is not particularly limited. The heat treatment time is, for example, 20 seconds to 4 minutes.
[0098]
　[Cold rolling or warm rolling step]
　with respect to hot-rolled steel sheet after hot-rolled sheet annealing step, carrying out the cold rolling or warm rolling. Here, the warm rolling is meant a process of implementing the rolled against hot-rolled steel sheet heated to 150 ~ 600 ℃.
[0099]
　Rolling reduction in cold rolling or warm rolling is preferably at 83% or more. Here, rolling reduction (%) is defined by the following equation.
　Rolling reduction (%) = (thickness of 1 last cold or intermediate steel plate thickness / initial cold or warm rolling before starting hot-rolled steel sheet warm after rolling) × 100
[0100]
　If rolling reduction is less than 83%, the amount of recrystallization nuclei required for the finish annealing step of the next step is insufficient. In this case, it is difficult to properly control the dispersion state of the crystalline structure A. If rolling reduction of 83% or more, it is possible to ensure a sufficient amount of recrystallization nuclei. This can be achieved by introducing a sufficient strain by cold rolling or warm rolling, recrystallization nuclei are thought to disperse and increased. Through the above steps, to produce an intermediate steel plate.
[0101]
　Finishing annealing step]
　with respect to the intermediate steel plate produced by cold rolling or warm rolling step, performing the finish annealing. Conditions of finish annealing is as follows.
[0102]
　The highest temperature (annealing temperature): 700 ~ 800 ℃
　when the maximum temperature reached at the time of finish annealing is less than 700 ℃, recrystallization does not proceed sufficiently. In this case, the magnetic properties of non-oriented electrical steel sheet is lowered. Furthermore, when performing finish annealing by continuous annealing, the effect of correcting the plate-shaped non-oriented electrical steel sheet can not be sufficiently obtained. On the other hand, if it exceeds the maximum temperature reached 800 ° C. at the time of final annealing, the area ratio of crystal structure A becomes less than 1%, the strength of the non-oriented electrical steel sheet is lowered.
　Without lowering the productivity, in terms of obtaining a desired tissue sufficiently heated, the soaking time at maximum temperature is preferably 1 to 50 seconds.
[0103]
　The average cooling rate CR at a temperature range of 700 ~ 500 ℃ 700-500 : 50 ° C. / sec or more
　average cooling in the temperature range of 700 ~ 500 ° C. speed CR 700-500 the crystal structure A in the non-oriented electrical steel sheet conceivable formation of dislocation structures and involved. The average cooling rate CR 700-500 if less than 50 ° C. / sec, the dislocation dispersion in the crystal structure A becomes uneven, so that the hardness ratio HVA / HVB exceeds 1.000. In this case, the crystal orientation developed by the additional heat treatment is hindered, the magnetic properties after additional heat treatment is lowered. On the other hand, the average cooling rate CR 700-500 If the 50 ° C. / sec or more, fixing and the like of confounding and final cell structure of dislocations into the precipitates ambient, uniform dislocation dispersion in the crystal structure A is promoted , by the additional heat treatment, acting preferably on the development of the crystal orientation of {100} and in the vicinity thereof contributes to improving magnetic characteristics. The average cooling rate CR 700-500 preferred lower limit of a 100 ° C. / sec, more preferably 200 ° C. / sec. The average cooling rate CR 700-500 When exceeding 500 ° C. / sec, there is a risk that too large a longitudinal temperature gradient in the steel sheet steel sheet is deformed, the average cooling rate CR 700-500 preferable upper limit of 500 ° C. / is seconds.
[0104]
　Through the above steps, the non-oriented electrical steel sheet according to the present embodiment is manufactured.
[0105]
　In the above-described manufacturing method, after the hot rolled sheet annealing step, a single cold rolling or warm rolling process, the plate thickness of the non-oriented electrical steel sheet and the thickness of the final.
[0106]
　[Insulating coating process]
　The above manufacturing method further relative to the surface of the non-oriented electrical steel sheet after the finish annealing step, even if a step (insulating coating process) of forming an insulating coating in order to reduce iron loss good. Insulating coating step is sufficient to carried out in a known manner. To ensure good punching property, it is preferable to form the organic coating containing a resin. Moreover, whereas in the case of emphasizing weldability, it is preferable to form a semi-organic or inorganic coating.
[0107]
　Inorganic components, for example, bichromate - borate, phosphate, silica-based or the like. The organic components, for example, general acrylic, acrylic styrene, acrylic silicone-based, silicone-based, polyester-based, epoxy-based, fluorine-based resin. In consideration of coatability, the preferred resin is an emulsion type resin. It may be subjected to insulating coating which exhibits adhesion ability by applying heat and / or pressure. Insulating coating having adhesion ability, for example, an acrylic, phenolic, epoxy, resins of melamine.
Example 1
[0108]
　The following is a more detailed description of the embodiments of the present invention embodiment. These examples are an example for confirming the effect of the present invention and are not intended to limit the present invention.
[0109]
　[Production process]
　were prepared slabs having the chemical compositions shown in Table 1.
[0110]
[Table 1]

[0111]
　Against slab having components described in Table 1, and heated at a slab heating temperature shown in Table 2, by carrying out the hot rolling to produce a hot rolled steel plate having a plate thickness of the 2.2 mm. Finishing temperature FT at the time of hot rolling (℃) and coiling temperature CT (℃) was as shown in Table 2.
[0112]
[Table 2]

[0113]
　Against hot-rolled steel sheet produced was performed hot rolled sheet annealing. The hot-rolled sheet annealing, in any of the test numbers, the average heating rate HR in the temperature range of 750 ~ 850 ° C. 750-850 was 50 ° C. / sec. Further, maximum temperature retention time at 900 ° C. was 2 minutes.
[0114]
　Against hot-rolled steel sheet after hot rolled sheet annealing, cold rolling for the test numbers 1-1 to 1-22,1-24 ~ 1-26, warm rolling at 200 ° C. for Test No. 1-23 It was prepared an intermediate steel sheet was performed. Rolling reduction of cold rolling is in any of the test numbers, was 88%. Through the above process, it was prepared intermediate steel sheet having a thickness of 0.27 mm (cold rolled steel).
[0115]
　With respect to the intermediate steel plate, it was carried out the finish annealing. Maximum temperature in the finish annealing are as shown in Table 2, the retention time was also 30 seconds any test number. The average cooling rate CR at a temperature range of ~ 500 ° C. 700 700-500 was 100 ° C. / sec in any of the test numbers.
[0116]
　Relative to the non-oriented electrical steel sheet after finish annealing was coated with a known insulating film containing a phosphoric acid-based inorganic and epoxy organic. Through the above process, it was prepared non-oriented electrical steel sheet of each test number. Result of checking analyzed non-oriented electrical steel sheet after finish annealing, the chemical composition was as shown in Table 1.
[0117]
　[Evaluation Test]
　relative to non-oriented electrical steel sheet of each test number produced was performed following evaluation tests.
[0118]
　[Evaluation test for non-oriented electrical steel sheet after finish annealing]
　[crystal structure measured Test
　samples were taken including a cross section parallel to the rolling surface of the non-oriented electrical steel sheet after finish annealing of each test number. The cross section in the thickness direction from the surface and cross section of 1/4 depth position of the sheet thickness. The sample surface corresponding to the cross section was observed surface.
[0119]
　With respect to the observation surface of the sample, after adjusting the surface by electrolytic polishing was performed crystal structure analysis using electron backscatter diffraction method (EBSD). The EBSD analysis, among the viewing surface, the boundary of the crystal orientation difference is 15 ° or more and the crystal grain boundary, the individual area surrounded by the grain boundaries is determined that one of the crystal grains, 10000 grain and an observation target region (observation region) comprising more. In observation region, diameter of a circle having an area equivalent to the area of each crystal grains (circle equivalent diameter) is defined as the particle size of each crystal grain.
　Particle size is defined as the crystal structure A region consists of more crystal grains 100 [mu] m, determined the area ratio (%). The diameter is defined a region consisting of less than 100μm grain and the crystal structure B, was determined and the average crystal grain size ([mu] m). These measurements were determined by the image analysis of the observation area.
[0120]
　[Hardness of the crystal structure]
　was performed Vickers hardness test according to JIS Z 2244 (2009) in any 20 points in the area of the crystal structure A. Test force (load) was 50g. The average value of the obtained Vickers hardness was a hardness HvA crystal structure A.
[0121]
　Similarly, it was performed Vickers hardness test according to JIS Z 2244 (2009) in any 20 points in the area of ​​the crystal structure B. Test force was set to 50g. The average value of the obtained Vickers hardness was a hardness HvB crystal structure B.
[0122]
　[Tensile Test]
　from non-oriented electrical steel sheet of each test number, to produce a JIS5 No. tensile test pieces defined in JIS Z 2241 (2011). Parallel portion of the tensile test piece was parallel to the rolling direction of the non-oriented electrical steel sheet. Using a tensile test pieces produced, in conformity with JIS Z 2241 (2011), normal temperature, and a tensile test in air was determined tensile strength TS (MPa).
[0123]
　Magnetic properties Evaluation Test]
　from non-oriented electrical steel sheet of each test number, in compliance with JIS C 2550-1 (2011), Epstein test cut respectively in the rolling direction (L direction) and the direction perpendicular to the rolling direction (C direction) It was prepared pieces. Against Epstein test piece, JIS C 2550-1 (2011) and 2550-3 (2011) was conducted electromagnetic steel strip test method conforming to, magnetic characteristics (magnetic flux density B 50 and the iron loss W 10/400 ) I was asked. The magnetic flux density B obtained by this test before adding the heat treatment 50 was defined as the magnetic flux density BA (T).
[0124]
　Magnetic characteristics evaluation tests in non-oriented electrical steel sheet after additional heat treatment]
　from non-oriented electrical steel sheet of each test number, in compliance with JIS C 2550-1 (2011), the rolling direction (L direction) and perpendicular to the rolling were prepared Epstein test pieces cut out respectively in the direction (C direction). Against Epstein test pieces in a nitrogen atmosphere, when 100 ° C. / heating rate, maximum temperature of 800 ° C., the retention time at the maximum temperature 800 ° C. as 2 hours to conduct additional heat-treatment.
[0125]
　Against Epstein test piece after additional heat treatment, in compliance with JIS C 2550-1 (2011) and 2550-3 (2011), the magnetic properties (magnetic flux density B 50 and the iron loss W 10/400 was determined). The magnetic flux density B obtained by this test after adding the heat treatment 50 was defined as the magnetic flux density BB (T).
[0126]
　[Test Results]
　Table 2 shows the results obtained by the above evaluation tests.
[0127]
　The chemical composition of the non-oriented electrical steel sheet of the test numbers 1-1 to 1-3,1-13,1-15 and 1-17 to 23 is appropriate, production conditions was also suitable. As a result, the area ratio of crystal structure A is 1 to 30%, an average grain size of crystal structure B were 25μm or less. Furthermore, the ratio of hardness HVB hardness HVA crystal structure A and the crystal structure B (HvA / HvB) were 1.000. Tensile strength TS is greater than or equal to 600MPa, it showed excellent strength.
[0128]
　Further, the magnetic flux density BB after additional heat treatment is at least 1.65 T, iron loss W 10/400 is less than 12.5 W / kg, was obtained excellent magnetic properties. Furthermore, the ratio of magnetic flux density BB after additional heat treatment on the magnetic flux density BA between additional heat treatment (BB / BA) is at 0.980 or more, even after additional heat treatment, reduction in the magnetic flux density is suppressed.
[0129]
　On the other hand, in Test No. 1-4 and 1-5, the slab heating temperature was too high. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
[0130]
　In Test No. 1-6, the chemical composition is appropriate, the slab heating temperature was also proper. However, the maximum temperature in the finish annealing exceeds 800 ℃. Therefore, the area ratio of crystal structure A is less than 1%, the tensile strength TS was as low as less than 600 MPa.
[0131]
　Both in Test No. 1-7 ~ 1-12,1-14 and 1-16, S content was too high. Therefore, the iron loss W 10/400 is greater than 12.5W / kg. In Test No. 1-10 and 1-11, the slab heating temperature was too high. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
[0132]
　In Test No. 1-24, C content is outside the range of the present invention. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, iron loss W 10/400 was larger than 12.5 W / kg.
　In Test No. 1-25, Si content is outside the range of the present invention. As a result, a sufficiently high strength can not be achieved.
　In Test No. 1-26, Mn content is out of the range of the present invention. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, iron loss W 10/400 is greater than 12.5 W / kg, BB / BA also was less than 0.980.
Example 2
[0133]
　Steel type A in Table 1, B, slabs C and D were prepared. Respect prepared slabs were heated at a slab heating temperature of 1120 ° C., to produce a hot rolled steel sheet by carrying out hot rolling. Finishing temperature FT at the time of hot rolling is 890 ~ ​​920 ° C., the coiling temperature CT was 590 ~ 630 ° C..
[0134]
　Against hot-rolled steel sheet produced was performed hot rolled sheet annealing under the conditions shown in Table 3. The hot-rolled steel sheet after performing a hot-rolled sheet annealing and pickling. Against hot-rolled steel sheet after pickling, by carrying out cold rolling at a reduction rate of 88%, it was prepared intermediate steel sheet having a thickness of 0.27 mm (cold rolled steel).
　Further, samples were taken from a portion of the hot-rolled steel sheet after hot rolled sheet annealing, the microstructure was observed by rolling direction perpendicular cross section was observed an average particle size of the recrystallization ratio and recrystallized grains.
　Specifically, the recrystallization rate is to observe the optical microscope structure was defined at the rate of the portion except for the black visible region nital etching. The average particle size of the recrystallized grains total thickness measures the mean intercept length in the line segment method with a microstructure photograph entering the field of view was defined as the particle size of those 1.13 times. At that time, the line segment is parallel to the thickness direction, the number of grain boundaries and the line segment intersect to exceed the 200 and determines the number of line segments.
　As a result, in Test No. 2-3,2-4,2-12, a recrystallization ratio of 95% or more, an average grain size of recrystallized grains was 50μm greater. In contrast, in Test No. 2-1, it was 93% recrystallization ratio.
[0135]
[table 3]

[0136]
　With respect to the intermediate steel plate, it was carried out the finish annealing. Maximum temperature in the finish annealing were as shown in Table 3. The retention time was 30 seconds either. The average cooling rate CR 700-500 none was 100 ° C. / sec.
[0137]
　Relative to the non-oriented electrical steel sheet after finish annealing was coated with a known insulating film containing a phosphoric acid-based inorganic and epoxy organic. Through the above process, it was prepared non-oriented electrical steel sheet of each test number. Result of checking analyzed non-oriented electrical steel sheet after finish annealing, the chemical composition was as shown in Table 1.
[0138]
　[Evaluation Test]
　in the same manner as in Example 1, with respect to non-oriented electrical steel sheet after finish annealing, the area ratio of crystal structure A (%), the average crystal grain size of the crystal structure B ([mu] m), the crystal structure A HvA Vickers hardness, Vickers hardness HvB the crystal structure B, tensile strength TS (MPa), the magnetic flux density BA and iron loss W before additional heat treatment 10/400 was determined.
[0139]
　Further, in the same manner as in Example 1, the magnetic properties of non-oriented electrical steel sheet after additional heat treatment (the magnetic flux density BB and iron loss W 10/400 was determined).
[0140]
　[Test Results]
　The results obtained are shown in Table 3.
[0141]
　The chemical composition of the non-oriented electrical steel sheet of the test numbers 2-3 and 2-4 and 2-12 are suitable, it was also suitable manufacturing conditions. As a result, the area ratio of crystal structure A is 1 to 30%, an average grain size of crystal structure B were 25μm or less. Furthermore, the ratio of hardness HVB hardness HVA crystal structure A and the crystal structure B (HvA / HvB) were 1.000. Therefore, the tensile strength TS is not less than 600 MPa, showed excellent strength.
[0142]
　Further, the magnetic flux density BB after additional heat treatment is at least 1.65 T, iron loss W 10/400 is less than 12.5 W / kg, was obtained excellent magnetic properties. Furthermore, the ratio of magnetic flux density BB after additional heat treatment on the magnetic flux density BA between additional heat treatment (BB / BA) is at 0.980 or more, even after additional heat treatment, reduction in the magnetic flux density is suppressed.
[0143]
　On the other hand, in Test No. 2-1, 2-2 and 2-11, the average heating rate HR 750-850 was less than 50 ° C. / sec. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
[0144]
　In Test No. 2-5, the maximum temperature in the finish annealing exceeds 800 ℃. Therefore, the area ratio of crystal structure A is less than 1%, the tensile strength TS was as low as less than 600 MPa.
[0145]
　In Test No. 2-6 ~ 2-10,2-13 and 2-14 were more S content. Therefore, the iron loss W 10/400 became 12.5W / kg or more. In Test No. 2-6 and 2-7 In addition, the average heating rate HR 750-850 was less than 50 ° C. / sec. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
[0146]
　In Test No. 2-11, the average heating rate HR 750-850 was less than 50 ° C. / sec. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
[0147]
　In test No. 2-15, the maximum temperature in the finish annealing exceeds 800 ℃. Therefore, the average grain size of the crystal structure B is larger than 25 [mu] m, the tensile strength TS was as low as less than 600 MPa.
Example 3
[0148]
　A slab of steel grade C ~ F in Table 1 were prepared. Respect prepared slabs were heated at a slab heating temperature of 1180 ° C., to produce a hot rolled steel sheet by carrying out hot rolling. Finishing temperature FT at the time of hot rolling is 890 ~ ​​920 ° C., the coiling temperature CT was 590 ~ 630 ° C..
[0149]
　Against hot-rolled steel sheet produced was performed hot rolled sheet annealing. The hot-rolled sheet annealing, in any of the test numbers, the average heating rate HR in the temperature range of 750 ~ 850 ° C. 750-850 was 50 ° C. / sec. Moreover, the highest temperature reached 900 ° C., retention time was 2 minutes.
[0150]
　The hot-rolled steel sheet after performing a hot-rolled sheet annealing and pickling. Against hot-rolled steel sheet after pickling, by carrying out cold rolling at a reduction rate of 87%, it was prepared intermediate steel sheet having a thickness of 0.25 mm (cold rolled steel).
[0151]
　With respect to the intermediate steel plate, it was carried out the finish annealing. Annealing temperature in the finish annealing (maximum temperature), retention time, and the average cooling rate CR 700-500 are as shown in Table 4.
[0152]
　Relative to the non-oriented electrical steel sheet after finish annealing was coated with a known insulating film containing a phosphoric acid-based inorganic and epoxy organic. Through the above process, it was prepared non-oriented electrical steel sheet of each test number. Result of checking analyzed non-oriented electrical steel sheet after finish annealing, the chemical composition was as shown in Table 1.
[0153]
[Table 4]

[0154]
　[Evaluation Test]
　in the same manner as in Example 1, with respect to non-oriented electrical steel sheet after finish annealing, the area ratio of crystal structure A (%), the average crystal grain size of the crystal structure B ([mu] m), the crystal structure A HvA Vickers hardness, Vickers hardness HvB the crystal structure B, tensile strength TS (MPa), the magnetic flux density BA and iron loss W before additional heat treatment 10/400 was determined.
[0155]
　Further, in the same manner as in Example 1, the magnetic properties of non-oriented electrical steel sheet after additional heat treatment (the magnetic flux density BB and iron loss W 10/400 was determined).
[0156]
　[Test Results]
　The results obtained are shown in Table 4.
[0157]
　The chemical composition of the non-oriented electrical steel sheet of the test numbers 3-3 and 3-4 and 3-12 are suitable, it was also suitable manufacturing conditions. As a result, the area ratio of crystal structure A is 1 to 30%, an average grain size of crystal structure B were 25μm or less. Furthermore, the ratio of hardness HVB hardness HVA crystal structure A and the crystal structure B (HvA / HvB) were 1.000. Therefore, the tensile strength TS is not less than 600 MPa, showed excellent strength.
[0158]
　Further, the magnetic flux density BB after additional heat treatment is at least 1.65 T, iron loss W 10/400 is below 10.0 W / kg, was obtained excellent magnetic properties. Furthermore, the ratio of magnetic flux density BB after additional heat treatment on the magnetic flux density BA between additional heat treatment (BB / BA) is at 0.980 or more, even after additional heat treatment, reduction in the magnetic flux density is suppressed.
[0159]
　On the other hand, in Test No. 3-1, 3-2 and 3-11, although the chemical composition is appropriate, the average cooling rate CR 700-500 was less than 50 ° C. / sec. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980. The iron loss W 10/400 is not reduced only to the value of 10.0W / kg more than the effect of the additional heat treatment has not been sufficiently exhibited.
[0160]
　In Test No. 3-5, the maximum temperature in the finish annealing exceeds 800 ℃. Therefore, the area ratio of crystal structure A is less than 1%, the tensile strength TS was as low as less than 600 MPa.
[0161]
　In Test No. 3-6 ~ 3-10,3-13 and 3-14 were more S content. Therefore, the iron loss W 10/400 exceeds 10.0W / kg.
[0162]
　Test Nos 3-6,3-7 and the 3-13 Further, the average cooling rate CR 700-500 was less than 50 ° C. / sec. Therefore, the hardness ratio HvA / HvB has exceeded the 1.000. As a result, the magnetic flux density BB after additional heat treatment is as low as less than 1.65 T, BB / BA also was less than 0.980.
Example 4
[0163]
　A slab of steel type A in Table 1 were prepared. In Test No. 4-1 to 4-5, with respect to the prepared slab is heated at a slab heating temperature of 1180 ° C., to produce a hot rolled steel sheet by carrying out hot rolling. On the other hand, in Test No. 4-6 ~ 4-9, a slab heating temperature of 1240 ° C., it exceeded 1200 ° C..
　In either test numbers, finishing temperature FT at the time of hot rolling is 890 ~ 920 ° C., the coiling temperature CT was 590 ~ 630 ° C..
[0164]
　Against hot-rolled steel sheet produced was performed hot rolled sheet annealing. The hot-rolled sheet annealing, the average heating rate HR in the temperature range of 750 - 850 ° C. 750-850 is a 60 ° C. / sec in Test No. 4-1 to 4-5, Test Nos 4-6 ~ 4-9 was 30 ℃ / sec. Further, in any of the test numbers, the highest temperature reached 900 ° C., retention time was 2 minutes.
[0165]
　The hot-rolled steel sheet after performing a hot-rolled sheet annealing and pickling. Against hot-rolled steel sheet after pickling, by carrying out cold rolling at a reduction rate of 87%, it was prepared intermediate steel sheet having a thickness of 0.25 mm (cold rolled steel).
[0166]
　With respect to the intermediate steel plate, it was carried out the finish annealing. In the finish annealing, the maximum temperature of the other test numbers except Test No. 4-1 is 750 ° C., Test No. 4-1 only, the maximum temperature was 840 ° C.. The holding time was also 30 seconds any test number. The average cooling rate CR at a temperature range of 700 - 500 ° C. 700-500 , the test numbers 4-1 to 4-5 at 100 ° C. / in seconds, test numbers 4-6 - 4-9 at 40 ° C. / It was second.
[0167]
　Relative to the non-oriented electrical steel sheet after finish annealing was coated with a known insulating film containing a phosphoric acid-based inorganic and epoxy organic. Through the above process, it was prepared non-oriented electrical steel sheet of each test number. Result of checking analyzed non-oriented electrical steel sheet after finish annealing, the chemical composition was as shown in Table 1.
[0168]
　[Evaluation Test]
　in the same manner as in Example 1, with respect to non-oriented electrical steel sheet after finish annealing, the area ratio of crystal structure A (%), the average crystal grain size of the crystal structure B ([mu] m), the crystal structure A HvA Vickers hardness, Vickers hardness HvB the crystal structure B, tensile strength TS (MPa), the magnetic flux density BA and iron loss W before additional heat treatment 10/400 was determined.
[0169]
　Magnetic characteristics evaluation tests in non-oriented electrical steel sheet after additional heat treatment]
　from non-oriented electrical steel sheet of each test number, in compliance with JIS C 2550-1 (2011), the rolling direction (L direction) and perpendicular to the rolling were prepared Epstein test pieces cut out respectively in the direction (C direction). Against Epstein test pieces in a nitrogen atmosphere, heating rate shown in Table 5 (° C. / hr), the highest temperature (° C.), and conducting additional heat treatment at a holding time at 800 ° C. (time).
[Table 5]

[0170]
　Against Epstein test piece after additional heat treatment, JIS C 2550-1 (2011) and 2550-3 (2011) was conducted electromagnetic steel strip test method conforming to, magnetic characteristics (magnetic flux density B 50 and the iron loss W 10/400 ) was determined. The magnetic flux density B obtained by this test after adding the heat treatment 50 was defined as the magnetic flux density BB (T).
[0171]
　[Test Results]
　The results obtained are shown in Table 5.
　The chemical composition of the non-oriented electrical steel sheet finish annealing while a material of Test Nos 4-2 to 4-5 is appropriate, production conditions was also suitable. As a result, the area ratio of crystal structure A is 1 to 30%, an average grain size of crystal structure B were 25μm or less. Furthermore, the ratio of hardness HVB hardness HVA crystal structure A and the crystal structure B (HvA / HvB) were 1.000. Tensile strength TS is greater than or equal to 600MPa, it showed excellent strength.
[0172]
　Further, Test Nos 4-3 to 4-5 which has been subjected to additional heat treatment to said materials under appropriate conditions, there is no means inferior and the magnetic flux density before additional heat treatment flux density after additional heat treatment, or a improved properties It was. Test No. 4-2 slow heating rate of the additional heat treatment is compared to other test numbers 4-3 to 4-5, although the magnetic flux density after additional heat treatment is lowered, BB / BA is an 0.980 or more , it was possible to suppress the decrease of the magnetic flux density sufficiently.
[0173]
　On the other hand, which is a material of the test numbers 4-6 - 4-9, non-oriented electrical steel sheet while the finish annealing production conditions is not appropriate, in case of performing the slow addition heat treatment of heating rate, the magnetic flux density after additional heat treatment reduction of is remarkable, BB / BA was less than 0.980. These results, in order to suppress the decrease in magnetic flux density, it is necessary to the heating rate in the additional heat treatment and rapid heating of the continuous annealing comparable, in the stress relief annealing which is practically implemented, the magnetic flux density it was found that the decrease is a material that can not be avoided. Also, the iron loss, in all material was reduced to a level commensurate with grain growth and distortion removal by additional heat treatment.
[0174]
　It has been described an embodiment of the present invention. However, the above-described embodiment is merely an example for implementing the present invention. Accordingly, the present invention is not limited to the embodiments described above, it can be implemented by changing the above-described embodiments without departing from the scope and spirit thereof as appropriate.
Industrial Applicability
[0175]
　According to the present invention has high strength, and non-oriented electrical steel sheet and a manufacturing method thereof having excellent magnetic properties even after additional heat treatment is obtained. Non-oriented electrical steel sheet of the present invention is widely applicable to applications where high strength and excellent magnetic properties are obtained. Particularly, in particular turbogenerator, electric vehicles, the drive motor of a hybrid vehicle, the typical example of the rotor of the high-speed rotation machine such as a machine tool motor, a large stress is suitable for such component applications. Also suitable for use to produce a rotor material and the stator material of the high-speed rotary motor from the same steel sheet.

The scope of the claims
[Requested item 1]
　A non-oriented electrical steel sheet,
　the chemical composition, in
　mass%, C: 0.0100% or
　less, Si: 3.0% greater, 5.0% or
　less, Mn: 0.1 ~ 3.0%,
　P: 0.20% or
　less, S: 0.0018% or
　less, N: 0.0040% or
　less, Al: 0 ~
　0.9%, 1 or more selected from Sn and Sb: 0 ~ 0.100% , 　Cr:
　0 ~ 5.0%, Ni: 0 ~ 5.0%, 　Cu: 0 ~ 5.0%, Ca: 0 ~ 0.010%, and, 　rare earth elements (REM): 0 ~ 0.010 % 　containing the balance being Fe and impurities, 　wherein in a cross section parallel to the rolling surface of the non-oriented electrical steel sheet, 　　the area ratio of crystal structure a consists of a particle diameter is 100μm or more crystal grains 1 It was 30%, 　　an average particle size of the a crystal structure other than the crystal structure a crystal structure B is at 25μm or less, 　　the crystal structure a Vickers hardness HvA to meet the Vickers hardness HvB Togashiki (1) of the crystal structure B, the non-oriented electrical steel sheet, characterized in that.
WhAt / HVB ≦ 1.000 (1)
[Requested item 2]
　The chemical
　composition, Al: 0.0001 ~
　0.9%, 1 or more selected from Sn and
　Sb: 0.005 ~ 0.100%, Cr: 0.5 ~
　5.0%, Ni: 0
　~
　5.0% .05, Cu: 0.5 ~ 5.0%, Ca: 0.0010 ~ 0.0100%, and,
　rare earth elements (REM): 0.0020 ~ 0.0100% or less
　group consisting containing one or more selected from
non-oriented electrical steel sheet according to claim 1, characterized in that.
[Requested item 3]
　A method of manufacturing a non-oriented electrical steel sheet according to claim 1,
　wherein after heating at 1000 ~ 1200 ° C. the slab having the chemical composition, hot-rolled steel sheet by carrying out hot rolling according to claim 1 a step of preparing,
　with respect to the hot-rolled steel sheet, a step of 750 average heating rate at ~ 850 ° C. and 50 ° C. / sec or higher, carrying out hot-rolled sheet annealing to the maximum temperature and 900 ~ 1150 ° C. ,
　a step of producing an intermediate steel plate by carrying out the cold rolling or warm rolling at a reduction rate of 83% or more with respect to the hot-rolled steel sheet after the hot rolled sheet annealing,
　with respect to said intermediate steel plate, the maximum temperature the 700 ~ 800 ° C., and a step of carrying out finish annealing of the average cooling rate in the temperature range of 700 ~ 500 ° C. and 50 ° C. / sec or higher, a
method for producing a non-oriented electrical steel sheet, characterized in that.