NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD OF MANUFACTURING THE SAME [Technical Field of the Invention]
[0001]
The present invention relates to a non-oriented electrical steel sheet which is used as a core material of an electrical device and a method of manufacturing the same, and more particularly, to a non-oriented electrical steel sheet having excellent core loss and a method of manufacturing the same.
Priority is claimed on Japanese Patent Application No. 2013-081078, filed on April 9, 2013, the content of which is incorporated herein by reference. [Related Art]
[0002]
Anon-oriented electrical steel sheet is used as a core material of various types of motors for heavy electrical apparatuses, home appliances, and the lilce. The non-oriented electrical steel sheet is commercially graded according to core loss, and is classified according to the design features of motors or transformers. Recently, fiom the viewpoint of energy saving, a further reduction in core loss and an increase in magnetic flux density have been strongly demanded of the non-oriented electrical steel sheet.
[0003]
In general, when fine precipitates are present in a steel sheet, grain gro\vth during anneaUng is retarded, and core loss is deteriorated. Particularly, Cu which is unavoidably incorporated into the steel sheet generates Cu sulfide, and the fine On sulfide inhibits the grain growth of the non-oriented electrical steel sheet. As a resuh,
- 1 -

core loss is deteriorated. In addition, the fine Cu sulfide which is present in tlie steel sheet causes a deterioration in hysteresis loss. The deterioration in hysteresis loss also causes the deterioration in core loss.
Here, in the related art, for the purpose of improving the core loss of a non-oriented electrical steel sheet, methods such as precipitation control of sulfide during hot rolling, a method of reducing the amount of sulfide through desulfurization, and suppression of precipitation of Cu sulfide tlirough rapid cooling after final annealing have been proposed.
[0004]
For example, in Patent Document 1, a method of controlling the dispersion state of Cu sulfide to a preferable state for magnetic properties of a non-oriented electrical steel sheet, that is, core loss and magnetic flux density by holding a slab containing 0.2% or less of Cu in a range of 900°C to 1 lOO'^C for 30 minutes or longer, thereafter holding the slab at a higher temperature of 1150°C and subsequently starting rolling, and limiting a cooling rate during finish hot rolling to be 50 °C/sec or lower is disclosed. However, in this method, there are problems in productivity, such as an increase in rolling load due to a reduction in slab heating temperature and a difficulty in strict control of the cooling rale.
[0005]
In Patent Document 2, a method of avoiding the generation of fine precipitates by adding CaSi to molten steel until the completion of casting to control the S content to be 0.005% or less, heating a slab to a temperature of 1000°C or higher and then hot-rolling the slab, and coiling a coil at a specific temperature range is disclosed. In this method, high purity steel is essential. However, the formation of fine Cu sulfide due to Cu wdiich is incorporated at an unavoidable level cannot be
- 2 -

avoided. Tlierefore, there is a problem in that magnetic properties are rather deteriorated by the incorporation of Cu.
[0006]
hi addition, in Patent Document 3, a teclttiique of suppressing the precipitation of Cu sulfide by performing rapid cooling from a temperature range of 500°C to 600^C to 300°C at a cooling rate of 10 °C/sec to 50 °C/sec after final amiealing is disclosed. However, the fact that Cu sulfide is precipitated even during cooling at a cooling rate of 50 °C/sec or higher is known in Non-Patent Documents 1 and 2, and the like. That is, in the technique of Patent Document 3 in which cooling is performed at a cooling rate of 10 °C/sec to 50 °C/sec, it is difficult to completely eliminate the precipitation of Cu sulfide.
[0007]
In Patent Documents 4 to 6, a technique in which an enhancement in magnetic properties is expected by suppressing the cooling rate after final annealing is disclosed. However, in this method, it may not be possible to make Cu sulfide harmless. [Prior Art Document] [Patent Document]
[0008]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2010474376
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. HlO-183244
[Patent Document 3] Japanese Unexamined Patent Application, First Publication No. H09-302414
[Patent Document 4] Japanese Unexamined Patent Application, First
- 3 -

Publication No. 2011-006721
[Patent Document 5] Japanese Unexamined Patent Application, First
Publication No. 2006-144036
[Patent Document 6] Japanese Unexamined Patent Application, First
Publication No. 2003-113451
[Non-Patent Document] [0009]
[Non-Patent Document 1] CAMP-ISIJ Vol.25 (2012), pl080 [Non-Patent Document 2] CAMP-ISIJ Vol.22 (2009), pl284 [Non-Patent Document 3] J. Flux Grovrth VoL5 (2010), p48 [Non-Patent Document 4] Materials Transactions Vol.53 (2012), P645 [Non-Patent Document 5] Tetsu-to-Hagane Vol.83 (1997), p479 [Non-Patent Document 6] Tetsu-to-Hagane Vol.92 (2006), p609
[Disclosure of the Invention]
[Problems to be Solved by the Invention] [0010] The present invention has been made taking the foregoing circumstances into
consideration, and an object thereof is to provide a non-oriented electrical steel sheet
having excellent core loss and a method of manufacturing the same without causing an
increase in cost or a reduction in productivity by making Cu sulfide harmless and
increasing the grain size.
[Means for Solving the Problem] [0011] In order to solve the above-described problems, in the present invention, an
effect of the chemical components and manufacturing conditions of a steel sheet on the
- 4 -

relationship between the state of sulfide and core loss was repeatedly examined. As a result, it was found that there was a case where non-oriented electrical steel sheets obtained under different manufacturing conditions had significantly different core losses even though the sizes or the nvimber densities of sulfide, which are hitherto known to affect core loss, were at the same level. Here, the inventors conducted more detailed examination on the morphology or structure of sulfide, and found a possibility that a difference in core loss might be caused by a difference in atomic structure of Cu sulfide, and specifically, a possibility that the consistency between the crystal lattice of Fe as a primary phase and Cu sulfide might affect magnetic domain wall motion. The present invention has been made based on the above-described findings, and is summarized in the following (1) to (8). [0012]
(1) That is, a non-oriented electrical steel sheet according to an aspect of the
present invention includes chemical compositions including, in terms of mass%: C:
0.0001% to 0.01%; Si: 0.05% to 7.0%; Mn: 0.01% to 3.0%; At: 0.0020% to 3.0%; S:
0.0001% to 0.1%; P: 0.0010% to 0.15%; N: 0.0010%) to 0.01%; Cu: 0.01% to 5.0%;
and a remainder including Fe and impurities, ixx which I2Q=46.4 which is a diffraction
intensity of Cu sulfide having a hexagonal structure shown at 20=46.4*' and l2o=32J
which is a diffraction intensity of Cu sulfide having a cubic structure shown at
20=32.3°, which are obtained through a X-ray diffraction of an electrolytic extraction
residue, satisfy the following Expression 1.
129=46.4 /120=32.3 5 0.5 .. .Expi'ession 1 [0013]
(2) In the non-oriented electrical steel sheet described in (1), when a Cu
content, in terms of mass%, is denoted as [%Cu] and an S content, in terms of mass%,
- 5 -

is denoted as [%S], the [%Cu] and the [%S] may satisfy [%Cu] / [%S] > 2.5. [0014]
(3) In the non-oriented electrical steel sheet described in (1) or (2), 0.5
pieces/|im to 50 pieces/|.mi of sulfide containing Cu and having a diameter of 5 mil to
500 nm may be contained.
[0015]
(4) A method of manufacturing a non-oriented electrical steel sheet according
to another aspect of the present invention, is a method of manufacturing the non-
oriented electrical steel sheet described in any one of (1) to (3), and includes:
performing a hot rolling on a slab to obtain a hot-rolled steel sheet; annealing the hot-
rolled steel sheet; pickling the hot-rolled steel sheet; performing a cold rolling on the
hot-rolled steel sheet to obtain a cold-rolled steel sheet; and annealing the cold-rolled
steel sheet, in which, in the annealing of the cold-rolled steel sheet, after the cold-
rolled steel sheet is held at T1°C, which is represented in the following Expression 2,
to 1530*^0 for 30 seconds to 3600 seconds, when an average cooling rate from the
T1°C to T2°C, which is shown in Expression 3, is denoted as CRl in the unit of °C/sec
and an average cooling rate from the T2°C to T3°C, which is shown in Expression 4, is
denoted as CR2 iu the v\uit of °C/sec, the cold-rolled steel sheet is cooled to a
temperature range of the T3°C or lower so that the CRl and the CR2 satisfy
Expressions 5, 6 and 7:
TI = 17000 /(14 - logio([%Cu]^ >^ [%S]))-273 ...Expression 2 T2 = 17000 / (14 - logio([%Cu]^ x [o/oS])) - 323 ...Expression 3 T3 = 17000 / (14 - logio([%Cu]^ x [%S])) - 473 .. .Expression 4 CRl > CR2 ...Expression 5 5 < CRl < 500 .. .Expression 6
- 6 -

0.5 < CR2 < 50 .. .Expression 7
where [%Cii] is a Cu content in terms of mass% and [%S] is an S content in terms of mass%. [0016]
(5) In the method of manufacturing a non-oriented electrical steel sheet
described in (4), the CRl may further satisfy the following Expression 8.
CR1>20 ...Expressions [0017]
(6) In the method of manufacturing a non-oriented electrical steel sheet
according to claim (4) or (5), the CR2 may further satisfy the following Expression 9.
CR2< 20...Expression 9 [0018]
(7) the method of manufacturing a non-oriented electrical steel sheet
described in any one of (4) to (6), may further include: subsequent to the annealing of
the cold-roHed steel sheet, holding the cold-rolled steel sheet in a temperature range of
the T2°C or lower to the T3°C or higher for 30 seconds or longer as an additional
armeaiing.
[0019]
(8) In the method of manufacturing a non-oriented electrical steel sheet
described in any one of (4) to (7), in the annealing of the hot-rolled steel sheet, the hot-
rolled steel sheet may be cooled so that CR3 which is an average cooling rate from the
T1°C to room temperature is 15 ''C/sec or higher.
[Effects of the Invention] [0020] According to the above aspects of the present invention, even when high
- 7 -

purification, a reduction in slab heating temperature, optimization of hot rolling conditions, and the like are not performed on the non-oriented electrical steel sheet, it is possible to make fine Cu sulfide harmless. Accordingly, a non-oriented electrical steel sheet having excellent core loss can be provided.
In addition, according to the above aspects of the present invention, properties (magnetic flux density, workability, and the like) other than core loss, required of a grain-oriented electrical steel sheet, can be ensured to be the same or a higher level than a material in the related art. [Brief Description of the Drawings]
[0021]
FIG. 1 is a graph showing the relationship between ho^e.A I l2e=32,3 ai^d core loss.
FIG. 2 is a flowchart showmg an example of a process of manufacturing a non-oriented electrical steel sheet according to an embodiment. [Embodiments of the Invention]
[0022]
Hereinafter, a non-oriented electrical steel sheet according to an embodiment of the present invention (may also be referred to as a non-oriented electrical steel sheet according to this embodiment) and a method of manufacturing the same will be described in detail. All of % of contents are mass%.
[0023] C: 0.0001% to 0.01%
C causes significant deterioration in core loss through magnetic aging. Therefore, the upper limit of the C content is 0.01%. From the viewpoint of the improvement in core loss, the C content is preferably 0.0020% or less. On the other

hand, when the C content is less than 0.0001%, the magnetic flux density is deteriorated. Therefore, in order to ensure a sufficient magnetic flux density, the lower limit of the C content is 0.0001%. The C content is preferably 0.0005 to 0.0015%, and more preferably 0.0007 to 0.0010%.
[0024] Si: 0.05% to 7.0%
The Si content is 0.05% to 7.0% for a balance between ensuring core loss and a sheet travelling property. When the Si content is less than 0.05%, good core loss is not obtained. On the other hand, when the Si content is more than 7.0%, the steel sheet becomes embrittled, and the sheet travelling property during a manufacturing process is significantly deteriorated. The Si content is preferably 2.3% to 3.5%, more preferably 2.9% to 3.3%, and still more preferably 3.0% to 3.2%.
[0025] Mn: 0.01% to 3.0%
Mn reacts with S and forms sulfide, and is thus an important element in the present invention, hi a case where Mn is present in steel, MnS is precipitated and thus the transition temperature of the crystal structure of Cu sulfide is reduced. In this case, Cu sulfide having a cubic structure is less lilcely to be generated. Therefore, the upper limit of the Mn contejit is 3.0%. On the other hand, when the Mn content is less than 0.01%, the steel sheet becomes embrittled during hot rolling. Therefore, the lower limit of the Mn content is 0.01%. The Mn content is preferably 0.05% to 2.0%., and more preferably 0.1% to 1.0%.
[0026] Al: 0.0020% to 3.0%
Al is solutionized in steel, resuhing in the electric resistance of steel is
- 9 -

increased and cove loss is reduced. Therefore, in order to improve core loss (reduce core loss), increasing the AI content in steel is advantageous. However, molten steel having a high Al content causes deterioration in operability during casting and thus causes embrittlement of the steel sheet. Therefore, the npper limit of the Al content is 3.0%. On the other hand, when the Al content is low, AIN which accelerates grain growth in the steel sheet is not sufficiently generated, and fine TiN that impedes the grain gro\vth is generated instead of AIN, resulting in significant deterioration in the magnetic flux density. Therefore, the lower limit of the Al content is 0.0020%. The Al content is preferably 0.1% to 2.0%, and more preferably 1.0% to 1.5%.
[0027] S: 0.0001% to 0.1%
The S content is directly associated with the amount of sulfide. When the S content is excessive, S is present in steel in a solid solution state, and steel becomes embrittled during hot rolling. Therefore, the upper limit of the S content is 0.1%. On the other hand, when the S content is less than 0.0001%, the precipitation temperature range (a temperature range of T2°C to T3°C, which will be described later) of Cu sulfide (cubic) is more significantly reduced than the grain grovs'th temperature of the steel sheet, and thus the effect ofimjjroving core loss is not obtained. Therefore, the lower limit of the S content is 0.0001%. The S content is preferably 0.01% to 0.05%, and more preferably 0.02% to 0.03%..
[0028] P: 0.0010% to 0.15%)
P has an effect of increasing the hardness of the steel sheet and eiiliancing a blankiirg property. In addition, a small amount of P has an effect of improving the magnetic flux density. In order to obtain this effect, the lower limit of the P content is
- 10 -

0.0010%. Here, when the P content is excessive, the magnetic flux density is deteriorated, and thus the upper limit of the P content is 0.15%. The P content is preferably 0.005% to 0.1%, and more preferably 0.01% to 0.07%.
[0029] N: 0.0010% to 0.01%
N is an element which forms nitride with Ti and the like. When the N content is excessive, the precipitation amount of nitride such as TiN is increased, and this nitride impedes the grain growth. Therefore, the upper limit of the N content is 0.01%. Here, a small amount of N contained suppresses precipitation of fine TiC, and thus an effect of accelerating the grain growth of the steel sheet is obtained. Therefore, for the purpose of ensuring a sufficient magnetic flux density, the lower limit of the N content is 0.0010%. The N content is preferably 0.0030% to 0.0080%, more preferably 0.0040% to 0.0080%, and still more preferably 0.0050% to 0.0070%.
[0030] Cu: 0.01% to 5.0%
Cu is an element which forms sulfide like Mn, and is a particularly important element. When the Cu content is too high, Cu is solutionized in the steel sheet, and the solid soKilion Cu causes embviltlement of the steel sheet during hot rolling. Therefore, the upper limit of the Cu content is 5.0%. On ihe other hand, in order to allow Cu sulfide to be precipitated prior to MnS during hot rolling, the generation temperature of Cu sulfide needs to be a high temperature, and the lower limit of the Cu content needs to be 0.01%. The Cu content is preferably 0.1 % to 1.5%, and more preferably 0.8% to 1.2%.
[0031]
The non-oriented electrical steel sheet according to this embodiment basically
- 11 -

contains the above-described chemical components, and the remainder including Fe and impurities. However, for the purpose of further enliancement in magnetic properties, the enhancement in properties such as strength, corrosion resistance, and fatigue properties required of a staictural member, the enhancement in casting properties or sheet travelling properties, and the enhancement in productivity by using scrap or the like, a small amount of elements such as Mo, W, In, Sn, Bi, Sb, Ag, Te, Ce, V, Cr, Co, Ni, Se, Re, Os, Nb, Zr, Hf, and Ta may be contained in a range of 0.5% or less in total, hi addition, when such elements are incorporated within a range of 0.5% or less in total, the effect of this embodiment is not damaged. Elements which generate sulfides such as Mg, Ca, Zn, and Ti affect the solid solution temperature of Cu sulfide, and thus the sum of the amounts thereof is preferably 0.2% or less.
[0032]
Next, the state of Cu sulfide which is an important control factor in the non-oriented electrical steel sheet according to this embodiment will be described.
The inventors found that there are at least two types of structures as the structure of Cu sulfide contained in the steel sheet. One is a cubic structure, and the other is a hexagonal structure (hexagonal close-packed structure). The cubic stracture has a stable phase, and the hexagonal structure has a metastablc phase.
It is difficult to completely remove the presence of sulfide in Ihe steel sheet. Therefore, in the non-oriented electrical steel sheet according to this embodiment, S is allowed to be actively precipitated as Cu sulfide and the precipitated Cu sulfide is controlled to mainly contain sulfide having the cubic structure, thereby avoiding the deterioration in core loss. Therefore, controlling the crystal structure of Cu sulfide is very important.
In this embodiment, for example, when X-ray diffraction (XRD) is performed
- 12 -

on the electrolytic extraction residue of the steel sheet, he=46A which is the diffraction intensity of Cu sulfide (hexagonal) at 20=46 A±2° and 120=32.3 wliich is the diffraction intensit}' of Cu sulfide (cubic) at 20=32.3±2° are controlled to satisfy the following Expression 1.
^20=46.4/^20=32.3 ^ 0.5 ...Expression 1
As shown in FIG. 1, as 120=45.4 / l2e=32.3 is reduced, core loss is improved.
The lower limit of 129=^6.4/120=32.3 does not need to be particularly limited. However, in a case where Cu sulfide having the hexagonal structure is absent, l20=46.4 / l26=32.3 becomes zero, and this value may be the lower limit.
In addition, in this embodiment, Cu sulfide (hexagonal) indicates Cu sulfide having the hexagonal structure, and Cu sulfide (cubic) indicates Cu sulfide having the cubic structure. In addition, the identification of diffraction peaks may be collated by using JCPDS'CARD which is a database of crystal lattices. For example, Cu sulfide (hexagonal) can be identified by using JCPDS-CARD: 00-023-0958 or the like, and Cu sulfide (cubic) can be identified by using JCPDS-CARD: 00-024-0051 or the like. In addition, in Cu sulfide in iron, the chemical bond ratio of S to Cu is changed in a range of 1; 1 to 2:1 due to the solid solution of Fe or Mn atoms, and the like. Therefore, 20 has a margin of error of ±2°. In general, an XRD diffraction intensity is a height from the background to tbe peak of a spectrum. The Xl^ diffraction intensity (peak intensity) in this embodiment is also obtained by removing the background using the software described m Non-Patent Documents 3 and 4.
[0033]
There is concern that fine FeS or fine MnS which is sulfide other than Cu sulfide may cause the deterioration in core loss. Therefore, it is preferable that Cu sulfide is allowed to be actively precipitated by sufficiently increasing the Cu content
- 13 -

with respect to the S content. Specifically, when the Cu content is denoted as [%Cu] and the S content is denoted as [%S] in terms of mass%, it is preferable that the Cu content and the Mn content are controlled to satisfy [%Cu] / [%S] > 2.5. 120 > [%Cu] / [%S] > 40 is more preferable, and 70 > [%Cu] / [%S] > 50 is still more preferable.
Furthermore, when the Mn content is denoted as [%Mn] in terms of mass%, a case where ([%Cu] x [%Mn]) / [%S] > 2 is satisfied is still more preferable from the viewpoint of the improvement in core loss. The reason why core loss is improved by satisfying ([%Cu] x [%Mn]) / [%S] > 2 is not clear. However, the inventors think the reason is that the generation of Cu sulfide (cubic) tends to be accelerated by the effect of Mn. ([%Cu] X [%Mn]) / [%S] > 15 is more preferable.
[0034]
In addition, in the non-oriented electrical steel sheet according to this embodiment, in order to further improve core loss, it is preferable that sulfide which contains Cu and has a diameter of 5 nm to 500 nm is present in the steel sheet at a number density per unit area of 0.5 pieces/|im to 50 pieces/|im . When the number density of sulfide is less than 0.5 pieces/pm^, the effect camiot be sufficiently obtained. Therefore, the number density of sulfide is preferably 0.5 pieces/pm or higher. On the other hand, when the number density is higher than 50 pieces/pm , grain growth properties are deteriorated, and thus there is concern of the deterioration in magnetic flux density. . Therefore, the upper limit of the number density is preferably 50 pieces/pm"^. In order to reliably improve core loss, the number density of sulfide is preferably in a range of 0.5 pieces/pm to 1.0 pieces/pm , and is more preferably in a rage of 0.5 pieces/pm to 0.7 pieces/pm . The observation of precipitates containing sulfide described above may be performed on the steel sheet having a corroded surface
- 14 -

with an SEM (scamiing electron microscope) or a TEM (transmission electron microscope) according to an extraction replica method or a thin film method, hi general, Cu sulfide is extremely fine (for example, smaller than 5 nm). However, in the non-oriented electrical steel sheet according to this embodiment, the crystal structure of Cu sulfide is mainly cubic, and thus sulfide becomes coarse. Accordingly, the diameter of Cu sulfide can be controlled to be in a range of 5 nm to 500 nm. Regarding core loss, a preferable Cu sulfide diameter is 50 nm to 300 mn, and a more preferable Cu sulfide diameter is 100 mn to 200 mn.
Cu sulfide needs to mainly contain sulfide having the cubic structure as its crystal stmcture, and thus the X-ray diffraction intensity obtained by XRD may safisfy 120=46.4/120=32.3 < 0.5 as described above. On the other hand, in a case where Cu sulfide is directly obsei-ved by a microscope, it is preferable that most of the observed Cu sulfide has the cubic stnicture, that is, the volume fraction of Cu sulfide having the cubic structure is 50% or more of the total of Cu sulfide. The volume fraction of Cu sulfide having the cubic structure is more preferably 66.7%, and still more preferably 80%. Here, Cu sulfide includes not only the precipitates of Cu sulfide alone, but also the precipitates which are composhely precipitated with other sulfides, oxides or carbides such as MnS and TiS. Furthermore, precipitates in wliich metal atoms sucli as Mn o)' Fe are solutionized in Cu sulfide, such as Cu(Mn)S or Cu(Fe)S, are also included.
In 3. case where Cu sulfide precipitates with MnS as composite precipitates, according to X-ray diffraction (XRD) performed by using the electrolytic extraction residue, it is preferable that 120=34.3 which is the diffraction intensity of Mn sulfide (cubic) at 20=34.3° and 120=32.3 which is the diffraction intensity of Cu sulfide (cubic) at 29-32.3° satisfy the conditions of the following Expression 1-2.
- 15 -

0.001 CR2... Expression 5
5
An ingot having the components shown in Table I was melted in vacuum, and the ingot was heated to 1150°C and was hot rolled at a hot rolling finish temperature of 875°C and a coiling temperature of 630°C, thereby producing a hot-rolled steel sheet having a sheet thickness of 2.0 mm. The hot-rolled steel sheet was subjected to hot-rolled sheet annealing, was subjected to pickling, and was cold-rolled at a rolling reduction of 75%, thereby producing a cold-rolled steel sheet having a sheet thickness of 0.50 mm. Heat treatments performed on the test materials and the precipitation states of observed precipitates are shown in Table 2, and the magnetic properties (magnetic flux density and core loss) of each of the obtained steel sheets are shown in Table 3. Evaluation results of core loss evaluated as VG for very good, G for good, F for effective, and B for level in the related art are also shown in Table 3.
In addition, the evaluation of magnetic properties was performed on the basis of JIS C 2550:2000. Regarding core loss, W15/50 (W/kg) was evaluated. W15/50 is a core loss at a frequency of 50 Hz and at a maximum magnetic flux density of 1.5T. In addition, the magnetic flux density was evaluated by using B50. B50 indicates a magnetic flux density at a magnetic field strength of 5000 A/m. In addition, the minimum target value of B50 was set to 1.65 T as in the related art.
The core loss evaluation criteria of the samples are as follows.
VG (Very Good): W15/50 (W/kg) < 2.28
G (Good): 2.28
An ingot having the chemical components shown in Table 4 was melted in vacuum, and the ingot was heated to 1150°C and was hot rolled at a hot rolling finish temperature of 850°C, thereby producing a hot-rolled steel sheet having a sheet thickness of 2.3 mm. The hot-rolled steel sheet Avas subjected to hot-rolled sheet
- 27 -

annealing, was subjected to pickling, and was cold-rolled at a rolling reduction of 85%, thereby producing a coid-rolled steel sheet having a sheet thickness of 0.5 mm. Thereafter, final annealing was performed at a holding temperature of Tl + 50°C for a holding time of 45 seconds: Thereafter, furnace cooling was performed so that the average cooling rates between T1°C and T2°C and between T2'^C and T3°C were respectively 35 °C/sec and 15 °C/sec. X-ray diffraction results, the precipitation states of precipitates, magnetic properties (magnetic flux density and core loss), brittleness, and overall evaluation results are shown in Table 5.
Regarding X-ray diffraction, measurement of the magnetic properties, and measurement of the precipitates, the same evaluations as in Example 1 were performed. Furthermore, in this example, a repeat bending test was performed on the basis of JIS C 2550:2000 to evaluate workability. In a case where breaking occurs with one time of bending, working properties were insufficient and were evaluated as fail, and a level at which breaking had not occurred after two times of bending was evaluated as pass (PASS).
In addition, in a case where a sample was broken during the repeat bending test, the sample was evaluated as B regardless of core loss, and the evaluation of core loss was performed only on samples which passed the repeat bending test. In addition, regarding the samples which could not be subjected to the repeat bending test due to breaking during rolling or the like, the test results thereof are indicated by "-"-
- 28 -

[0051] [Table 4]
REMAINDER INCLUDES Fc AND IMPURITIES.
COMPONENTS WHICH ARE OUTSIDE OF SPEOIRED RANGES ARE UNDERLINED.
- 29 -


[0053]
An ingot having the same components as Steel type No. H23 shown in Table 4 was heated to 1100°C and was hot-rolled at a finish temperature of 850°C and a coiling temperature of 630°C, thereby producing a hot-rolled sheet having a sheet thickness of 2.0 mm. The hot-rolled sheet was subjected to final annealing under the conditions shown in Table 5, and was subjected to hot-rolled sheet amiealing at 1000°C for 120 seconds in some examples. Other manufacturing conditions. X-ray diffraction results, the precipitation states of precipitates, and the evaluation results of magnetic properties (magnetic flux density and core loss) are shown in Table 6. Regarding X-ray diffraction, measurement of the magnetic properties, and measurement of the precipitates, the same evaluations as in Example 1 were performed.
- 31 -

[0055]
According to Examples 1 to 3 described above, in a case where the chemical components and the manufacturing method were preferable as in Manufacture Nos. 1 to 8, 12, 114, 16, 18, 201 to 223, and 23A to 23P, it was seen that the ratio of Cu sulfide (cubic) satisfied the present invention and thus a non-oriented electrical steel sheet having excellent core loss couid be obtained. On the other hand, in a case where any of the chemical components and the manufacturing method were outside of the range of the present invention, sufficient core loss could not be obtained, and thus basic properties required of the non-oriented electrical steel sheet could not be obtained. Otherwise, as in Manufacture Nos. 227, 228, and 233, breaking had occurred during rolling, and magnetic properties, XRD (X-ray diffraction), and number densities could not be evaluated. [Industrial Applicability]
[0056]
According to the present invention, even when high purification, a reduction in slab heating temperature, optimization of hot rolling conditions, and the like are not performed on the non-oricnled electrical steel sheet, it is possible to make fine Cu sulfide harmless. Accordingly, a non-oriented electrical slecl sheet having excellent core loss can be provided.

CLAIMS
1. A non-oriented electrical steel sheet comprising chemical
compositions including, in terms of mass%;
C:0.0001%to0.01%;
Si: 0.05% to 7.0%;
Mn: 0.01% to 3.0%;
Al: 0.0020% to 3.0%;
8:0.0001% to 0.1%;
P: 0.0010% to 0.15%;
N: 0.0010% 10 0.01%;
Cu: 0.01% to 5.0%; and
a remainder including Fe and impurities,
wherein l2e=46.4 which is a diffraction intensity of Cu sulfide having a hexagonal structure shown at 20=46.4° and l2e=32.3 wliich is a diffi-action intensity of Cu sulfide having a cubic structure shown at 29=32.3'^, which are obtained through a X-ray diffraction of an electrolytic extraction residue, satisfy the following Expression 1.
I2f}='f6.4/l2()=32j <0.5 ...Expression 1
2. The non-oriented electrical steel sheet according to claim 1,
wherein, when a Cu content, in terms of mass%, is denoted as [%Cu] and an S
content, in terms of mass%, is denoted as [%S], the [%Cu] and the [%S] satisfy [%Cu]
/[%S]>2.5.
' 34 -

3. The non-oriented electrical steel sheet according to claim 1 or 2,
wherein 0.5 pieces/^m to 50 pieces/f-un of sulfide containing Cu and having
a diameter of 5 nm to 500 nm are contained.
4. A method of manufacturing the non-oriented electrical steel sheet
according to any one of claims 1 to 3, the method comprising:
performing a hot rolling on a slab to obtain a hot-rolled steel sheet;
annealing the hot-rolled steel sheet;
pickling the hot-rolled steel sheet;
performing a cold rolling on the hot-rolled steel sheet to obtain a cold-rolled steel sheet; and
annealing the cold-rolled steel sheet,
wherein, in the amiealing of the cold-rolled steel sheet, after the cold-rolled steel sheet is held at T1°C, which is represented in the following Expression 2, to 1530°C for 30 seconds to 3600 seconds, when an average cooling rate from the T1°C to T2°C, which is shown in Expression 3, is denoted as CRl in the unit of °C/sec and an average cooling rate from the T2°C to T3*^C, which is shown in Expression 4, is denoted as CR2 in the unit of °C/sec, the cold-rolled steel sheet is cooled to a temperature range of the T3°C or lower so that t!ie CRl and the CR2 satisfy Expressions 5, 6 and 7:
Tl - 17000 / (14 - logio([%Cu]^ X [o/oS])) - 273 ...Expression 2
T2= 17000/(14-logio([%Cufx [o/oS]))-323 ...Expression 3
T3 = 17000 / (14 - logio([%Cu]^ x [%S])) - 473 .. .Expression 4
CRl > CR2 ...Expression 5
5 < CRl < 500 ...Expression 6
- 35 -

0.5 < CR2 < 50 .. .Expression 7
where [%Cu] is a Cu content in teitns of mass% and [%S] is an S content in terms of mass%.
5. The'tiiethQd of manufacturing a non-oriented electrical steel sheet
according to claim 4,
wherein the CRl forther satisfies the following Expression 8. CR1> 20...Expression 8
6. The method of manufacturing a non-oriented electrical steel sheet
according to.claim 4 or 5,
wherein the CR2 forther satisfies the following Expression 9. CR2<20 ...Expression9
7. The method of manufacturing a non-oriented electrical steel sheet
according to any one of claims 4 to 6, further comprising:
subsequent to the annealing of the cold-rolled steel sheet, holding the cold-rolled steel sheet in a temperature range of the T2°C or lower to the T3°C or higher for 30 seconds or longer as an additional annealing.
8. The method of manufacturing a non-oriented electrical steel sheet
according to any one of claims 4 to 7,
wherein, in the amiealing of the hot-roUed steel sheet, the hot-roiled steel sheet is cooled so that CR3 wliich is an average cooling rate from the T1°C to a room temperature is 15 °C/sec or higher.