DESCRIPTION
TITLE OF INVENTION: METHOD OF MANUFACTURING NON-ORIENTED ELECTRICAL STEEL SHEET
TECHNICAL FIELD
[0001] The present invention relates to a method of manufacturing a non-oriented electrical steel sheet used as a core material of a rotary machine and a small-sized transformer, for example.
BACKGROUND ART
[0002] A non-oriented electrical steel sheet has been used in a wide range of fields such as a transformer and a motor mainly. In recent years, a non-oriented electrical steel sheet high in magnetic flux density B50 has been required as a non-oriented electrical steel sheet more excellent in performance.
[0003] In order to obtain the non-oriented electrical steel sheet high in magnetic flux density B50, it is effective to increase a crystal grain diameter of a hot-rolled steel sheet obtained by hot rolling, and in order to increase the crystal grain diameter, it is effective to set a finishing temperature of the hot rolling (a temperature at the time when the hot rolling is finished) to be equal to or lower than a transformation temperature Arl at which austenite is transformed into ferrite and to a temperature as high as possible.
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[0004] On the other hand, at the transformation temperature Arl, a mechanical property of the steel sheet changes greatly, and thus when the mechanical property changes in the middle of the hot rolling, there sometimes arises a case that a shape of the hot-rolled steel sheet obtained by the hot rolling deteriorates and the steel sheet fractures in the middle of the hot rolling, resulting in that a problem of reduction in productivity is caused.
CITATION LIST
PATENT LITERATURE
[0005] Patent Literature 1: Japanese Laid-open
Patent Publication No. 2007-217744
Patent Literature 2: Japanese Laid-open Patent Publication No. 2007-177282
Patent Literature 3: Japanese Laid-open Patent Publication No. 09-125144
Patent Literature 4: Japanese Laid-open Patent Publication No. 02-182830
Patent Literature 5: Japanese Laid-open Patent Publication No. 02-182831
SUMMARY OF INVENTION TECHNICAL PROBLEM
[0006] In consideration of the above-described problem, the present invention has an object to provide a method of manufacturing a non-oriented electrical steel sheet excellent in magnetic flux
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density and productivity.
SOLUTION TO PROBLEM
[0007] The gist of the present invention that solves the above-described problem is as follows. (1) A method of manufacturing a non-oriented electrical steel sheet includes: from 1100 °C to 1250 °C, heating a slab that contains C: 0.001 mass% to 0.005 mass%, Si: 0.1 mass% to 2.0 mass%, Al: 0.001 mass% to 1.0 mass%, Mn: 0.1 mass% to 1.0 mass%, S: 0.001 mass% to 0.015 mass%, N: 0.001 mass% to 0.005 mass%, and Ti : 0.0001 mass% to 0.0050 mass% and a balance being composed of Fe and inevitable impurities and in which when a Si content (mass%), an Al content (mass%), and a Mn content (mass%) are represented as [Si], [Al], and [Mn] respectively, relation of [Si] + 2 x [Al] -[Mn] ^ 2.0 is established;
performing hot rolling of the heated slab and obtaining a hot-rolled steel sheet;
performing cold rolling of the hot-rolled steel sheet and obtaining a cold-rolled steel sheet; and
performing finish annealing of the cold-rolled steel sheet, in which
in the hot rolling, an outlet side temperature of a rolling pass through which a steel sheet having five times or more thickness of the hot-rolled steel sheet is rolled to five times or less thickness is set to be equal to or lower than a transformation temperature Arl, and a finish temperature of the hot
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rolling is set to the transformation temperature Arl
- 50°C to the transformation temperature Arl.
(2) The method of manufacturing the non-oriented
electrical steel sheet according to (1), in which
the slab further contains 0.001 mass% to 0.2 mass% of one type or a plurality of types selected from the group consisting of Sn, Cu, Sb, and Cr.
(3) The method of manufacturing the non-oriented
electrical steel sheet according to (1) or (2), in
which
the slab further contains 0.001 mass% to 0.1 mass% of one type or a plurality of types selected from the group consisting of P, Ni, Mo, and V.
ADVANTAGEOUS EFFECTS OF INVENTION
[0008] According to the present invention, it is possible to increase productivity of a non-oriented electrical steel sheet having an excellent magnetic propert y.
BRIEF DESCRIPTION OF DRAWINGS
[0009] [Fig. 1] Fig. 1 is a view explaining rolling passes in finish rolling.
DESCRIPTION OF EMBODIMENTS
[0010] Hereinafter, an embodiment of the present
invention will be explained.
[0011] In order to increase a magnetic flux density
B50 as a magnetic property of a non-oriented
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electrical steel sheet, it is effective to set a finish temperature of hot rolling performed prior to cold rolling to be equal to or lower than a transformation temperature Arl and to a temperature as high as possible to then increase a crystal grain diameter. However, when the finish temperature of the hot rolling is set as above, there arises a problem that trouble such as deterioration in its sheet shape after the hot rolling and fracture is likely to occur, and there has been sometimes a case that the finish temperature of the hot rolling has to be reduced at the sacrifice of the magnetic flux density B50 conventionally. The present inventors focused attention on the fact that its mechanical property changes greatly before and after transformation, and thought that when temperature reaches the transformation temperature Arl at a stage where the steel sheet is thinly rolled to some extent in the hot rolling, the mechanical property of the steel sheet is likely to change greatly, resulting in that deterioration in shape, fracture and so on are likely to occur.
[0012] In order to prevent deterioration in shape and fracture of a hot-rolled steel sheet obtained by the hot rolling, the present inventors further examined at which stage of the hot rolling temperature is made to reach the transformation temperature Arl. In general, even though the mechanical property of the steel sheet has changed
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around the transformation temperature Arl, it is possible to bring the steel sheet close to an ideal shape by a rolling pass/rolling passes thereafter in the case when a certain degree of thickness of the steel sheet is secured at that time. Further, the larger the thickness of the steel sheet becomes, the larger deformation resistance becomes, so that fracture does not easily occur. On the other hand, since it is effective to set the finish temperature of the hot rolling to the temperature as described above in order to increase the magnetic flux density B50, it is necessary to prevent the finish temperature of the hot rolling from being too low while securing a certain degree of thickness of the steel sheet at the stage where temperature reaches the transformation temperature Arl.
[0013] Then, as a result of examination of a balance between the thickness of the steel sheet at the stage where temperature reaches the transformation temperature Arl and the finish temperature of the hot rolling, it was found out that among a plurality of rolling passes existing in a hot rolling process, an outlet side temperature of the rolling pass through which the steel sheet having five times or more thickness of the hot-rolled steel sheet is rolled to five times or less thickness is set to be equal to or lower than the transformation temperature Arl, and thereby it is possible to prevent deterioration in shape of the hot-rolled steel sheet and fracture of
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the steel sheet in the middle of the hot rolling, and to secure the high magnetic flux density B50.
[0014] Hereinafter, a method of manufacturing a non-oriented electrical steel sheet in this embodiment will be explained.
[0015] In this embodiment, first, a molten steel having a predetermined composition is cast to manufacture a slab. A casting method is not limited in particular. The slab contains, for example, C: 0.001 mass% to 0.0 05 mass% or less. Si: 0.1 mass% to 2.0 mass%, Al: 0.001 mass% to 1.0 mass%, Mn: 0.1 mass% to 1.0 mass%, S: 0.001 mass% to 0.015 mass%, N: 0.001 mass% to 0.005 mass%, and Ti: 0.0001 mass% to 0.0050 mass%, and a balance being composed of Fe and inevitable impurities. Further, when a Si content
(mass%), an Al content (mass%), and a Mn content
(mass%) are represented as [Si], [Al], and [Mn] respectively, [Si] + 2 x [A1] - [Mn] ^ 2.0 is satisfied.
[0016] Further, in order to improve the magnetic property, not less than 0.001 mass% nor more than 0.2 mass% of one type or a plurality of types selected from the group consisting of Sn, Cu, Sb, and Cr may be added, or not less than 0.001 mass% nor more than 0.1 mass% of one type or a plurality of types selected from the group consisting of P, Ni, Mo, and V may also be added.
[0017] Here, reasons for limiting the numerical values of the composition of the above-described slab
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will be explained.
[0018] C forms carbide such as TiC in the non-oriented electrical steel sheet to deteriorate the magnetic property. Further, magnetic aging becomes noticeable due to precipitation of C. The above phenomenon becomes prominent in the case of a C content being larger than 0.005 mass%. On the other hand, when the C content is set to be 0.001 mass% or less, a load in decarburization in manufacturing steel is noticeably increased to thus increase cost. Thus, the C content is set to 0.001 mass% to 0.005 mas s % .
[0019] Si is an element quite effective for increasing electrical resistance to reduce an eddy current loss constituting part of core loss. When a Si content is less than 0.1 mass%, it not possible to sufficiently suppress the eddy current loss. On the other hand, when the Si content exceeds 2.0 mass%, cold rolling becomes difficult to be performed. Thus, the Si content is set to be not less than 0.1 mass% nor more than 2.0 mass%.
[0020] Al, similarly to Si, reduces the core loss. When an Al content is less than 0.001%, oxygen-based inclusions increase and thereby the core loss deteriorates. On the other hand, when the Al content exceeds 1.0 mass%, the magnetic flux density is reduced and the cost increases noticeably. Thus, the Al content is set to be not less than 0.001 mass% nor more than 1.0 mass%.
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10021] Mn increases hardness of the non-oriented electrical steel sheet to improve a stamping property. When a Mn content is less than 0.1 mass%, the above effect becomes insufficient. On the other hand, when the Mn content exceeds 1.0 mass%, a crystal structure is easily miniaturized and the cost increases noticeably. Thus, the Mn content is set to be not less than 0.1 mass% nor more than 1.0 mass%.
[0022] S easily forms fine precipitates such as MnS, TiS, and CuS, and these precipitates prevent grain growth and thus the magnetic property deteriorates, so that a S content is set to be 0.015 mass% or less. On the other hand, when the S content is set to be less than 0.001 mass%, cost of desulfurization increases, so that the S content is set to be not less than 0.001 mass% nor more than 0.015 mass%.
[0023] N forms a large amount of precipitates such as AIN and TIN to thereby deteriorate the magnetic property, so that a N content is set to be 0.005 mass% or less. On the other hand, when the N content is set to be less than 0.001 mass%, an effect is weakened, so that the N content is set to be not less than 0.001 mass% nor more than 0.005 mass%.
[0024] Ti forms a large amount of precipitates such as TiS and TIN to thereby deteriorate the magnetic property, so that a Ti content is set to be 0.0050 mass% or less. On the other hand, when the Ti content is set to be less than 0.0001 mass%, an alloy with high purity has to be used and thus the cost
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increases, resulting in that the Ti content is set to be not less than 0.0001 mass% nor more than 0.0050 mas s %.
[0025] In order to further improve the magnetic property, not less than 0.001 mass% nor more than 0.2 mass% of one type or a plurality of types selected from the group consisting of Sn, Cu, Sb, and Cr may be contained, or not less than 0.001 mass% nor more than 0.1 mass% of one type or a plurality of types selected from the group consisting of P, Ni, Mo, and V may also be contained. However, if the above element/elements is/are contained in large amount, an effect of increasing the magnetic property is saturated, so that a content/contents of the element/elements is/are preferably set to be the upper limit value or less in order to avoid the increase in cost.
[0026] Further, in the case of [Si] + 2 x [A1] -
[Mn] > 2.0, an a single-phase based composition is made, so that deterioration in shape in the hot rolling, which is the problem in the present invention, does not occur. However, when such a condition is employed, Si and Al are required to be added in large amount, so that significant increase in cost, deterioration in cold rolling performance, and reduction in magnetic flux density become problems. Thus, [Si] + 2 x [Al] - [Mn] ^ 2.0 is set.
[0027] Next, the slab having such a composition is manufactured to be heated. Although the
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transformation temperature Arl varies according to composition, the above heating temperature is set to from 1100°C to 1250°C. When the heating temperature is lower than 1100°C, at the time when rough rolling and finish rolling in the subsequent hot rolling are finished, temperature becomes too low, and the crystal grain diameter becomes small. On the other
hand, when the heating temperature exceeds 1250°C, a finishing temperature (the finish temperature) of the hot rolling is likely to be higher than the transformation temperature Arl. Then, in the case when the finishing temperature is higher than the transformation temperature Arl, a phase transformation occurs after the hot rolling being finished, and the crystal grain diameter becomes small. Thus, the heating temperature before the hot rolling is set to be not lower than 1100°C nor higher than 1250°C.
[0028] Note that the transformation temperature Arl is obtained by, for example, thermodynamic equilibrium calculation, but the way to obtain it is not limited to this. Further, the transformation temperature Arl is defined to a temperature at which a perfect transformation of austenite into ferrite is completed at the time of cooling after the heating.
[0029] Next, the hot rolling is performed on the heated slab and the hot-rolled steel sheet is obtained. First, by the rough rolling being the preceding stage of the hot rolling, the steel sheet
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having a thickness of 30 mm to 60 mm is obtained. Next, by the finish rolling being the following stage, the hot-rolled steel sheet having a thickness of about 2 mm or so is obtained.
[0030] Fig. 1 is a view explaining the rolling passes in the finish rolling.
As illustrated in Fig. 1, in the finish rolling, the hot-rolled steel sheet is obtained through a first rolling pass 10a to a sixth rolling pass lOf. Note that in Fig. 1, an example where the finish rolling is performed by six rolling passes is illustrated, but the number of rolling passes is not limited to the above example.
[0031] First, the rough rolled steel sheet having a thickness of 30 mm to 60 mm passes through the first rolling pass 10a and finally passes through the sixth rolling pass lOf, and thereby the thickness becomes 2 mm or so. In this embodiment, a temperature after the steel sheet has passed through the sixth rolling pass lOf is defined to the finishing temperature of the hot rolling, and the temperature is set to the transformation temperature Arl - 50°C to the transformation temperature Arl. When the finishing temperature of the hot rolling is lower than the
transformation temperature Arl - 50°C, the crystal grain diameter becomes small, and thus the magnetic flux density B50 to be targeted in the non-oriented electrical steel sheet cannot be obtained. Further, when the finishing temperature of the hot rolling is
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higher than the transformation temperature Arl, the phase transformation of austenite into ferrite occurs after the hot rolling being finished, so that grain refining of the structure occurs. Thus, the finishing temperature of the hot rolling is set to be not lower than the transformation temperature Arl -50°C nor higher than the transformation temperature Arl .
[0032] As the further improved case, when the finishing temperature of the hot rolling is set to be
the transformation temperature Arl - 30°C or higher, the larger crystal grain diameter is obtained and the higher magnetic flux density B50 is obtained. [0033] Further, in this embodiment, the outlet side temperature of the rolling pass through which the steel sheet having five times or more thickness of the hot-rolled steel sheet is rolled to five times or less thickness is set to be the transformation temperature Arl or lower. When the outlet side temperature of the above rolling pass exceeds the transformation temperature Arl, the phase transformation occurs in a state where the steel sheet becomes thin, and thus the steel sheet cannot resist change in mechanical property and then fracture or the like occurs in the middle of the hot rolling. Furthermore, when the mechanical property changes, the rolling at the rolling pass through which the steel sheet passes thereafter thereby becomes unstable, and the shape of the steel sheet
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sometimes deteriorates.
[0034] On the other hand, if the steel sheet has a thickness equal to or more than five times that of the hot-rolled steel sheet, even though the transformation occurs during the hot rolling, the degree of the deterioration in the sheet shape and the possibility of fracture are sufficiently reduced because the steel sheet is thick sufficiently. Even in the case when deterioration in shape further occurs, room to correct the shape through the subsequent rolling pass/rolling passes is sufficiently secured.
[0035] In the case when the thickness of the hot-rolled steel sheet to be obtained is 2 mm and the rolling pass through which the steel sheet having a thickness of 10 mm or more is rolled to a thickness of 10 mm or less is the third rolling pass 10c in the example illustrated in Fig. 1, an outlet side temperature of the third rolling pass 10c is set to be the transformation temperature Arl or lower. [0036] Next, pickling is performed on the obtained hot-rolled steel sheet without performing annealing thereon, and cold rolling is performed one time, or cold rolling is performed two times with intermediate annealing included, and thereby a cold-rolled steel sheet is obtained. In this embodiment, annealing is not performed before the cold rolling in order to reduce processes. Then, finish annealing is performed on the obtained cold-rolled steel sheet,
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'and the non-oriented electrical steel sheet is obtained.
[0037] Next, experiments conducted by the present inventors will be explained. Conditions and so on in these experiments are examples employed for confirming the applicability and effects of the present invention, and the present invention is not limited to these examples. [Example 1]
[0038] Slabs for non-oriented electrical steel sheets each containing C: 0.002 mass%. Si: 0.6 mass%, Mn: 0.18 mass%, Al: 0.3 mass%, N: 0.0013 mass%, S: 0.0017 mass%, Ti: 0.0014 mass%, Sn: 0.03 mass%, Cu: 0,096 mass%, and P: 0.013 mass%, and a balance being composed of Fe and inevitable impurities were slab heated at 1200°C. Then, rough rolling was performed until the thiclcness of each of steel sheets became 40 mm. Next, the steel sheets had finish rolling performed thereon through six rolling passes, and had water poured thereonto to be cooled, and then the steel sheets were each coiled at 700°C. At this time, the thickness of each of hot-rolled steel sheets was 2.2 mm. Further, in Table 1 below, each thickness of the steel sheet obtained after passing through the respective rolling passes in the finish rolling is shown. [0039]
[Table 1]
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' TNT FT ^FTER AFTER AFTER AFTER AFTER AFTER
IT pjj^grp SECOND THIRD FOURTH FIFTH SIXTH
PA S S SI DE
PASS PASS PASS PASS PASS PASS
SHEET THICKNESS 40 23.6 13.9 8.2 4.9 3.0 2.2
(mm)
[0040] Further, in the finish rolling, an outlet side temperature of the third rolling pass, at which the thickness of the steel sheet falls below 11 mm being five times the thickness of the hot-rolled steel sheet, and an outlet side temperature of the sixth rolling pass were changed according samples and the finish rolling was performed. Further, the hot-rolled steel sheets were each coiled, and then whether the coil shape is good or not was also observed. Whether the coil shape of the hot-rolled steel sheet after the finish rolling is good or not was determined by change in sheet thickness and sheet width, the degree of crown and camber, and whether flatness and the like deteriorate or not. [0041] Thereafter, the obtained hot-rolled steel sheets each had pickling performed thereon and had cold rolling performed thereon, and thereby cold-rolled steel sheets each having a thickness of 0.50 mm were obtained. Next, continuous annealing was performed on the obtained cold-rolled steel sheets at 900°C for 15 seconds, and thereby non-oriented electrical steel sheets were obtained. Then, evaluation of magnetic property of each of the obtained non-oriented electrical steel sheets was conducted. In Table 2 below, a result whether the
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shape, of the non-oriented electrical steel sheet obtained this time, after the hot rolling being finished is good or not, and a value of the magnetic flux density B50 obtained by magnetic measurement being conducted after the continuous annealing are shown. [0042]
[Table 2]
OUTLET SIDE MAGNETIC I
TEMPERATURE FINISHING FLUX ^"^^^ °^ TRANSFORMATION
SAMPLE ^_^^^j^ ^^j^^ TEMPERATURE DENSITY "OT-ROLLED TEMPERATURE
NO- PASS ("C) B50 S^'=^^ f^',
("C) (T) ^"^^^ ^21
1 1000 965 1.69 o COMPARATIVE
EXAMPLE 1
2 970 955 1.70 x COMPARATIVE
EXAMPLE 2
-i OCR QTt 1 -R COMPARATIVE
3 955 935 1./5 x
EXAMPLE 3
PRESENT
4 935 915 1.75 o INVENTION
EXAMPLE 1
PRESENT
5 915 895 1.74 o INVENTION
EXAMPLE 2
COMPARATIVE
'' 850 850 1.69 o -^vAMD7r EXAMPLE 5
[0043] In PRESENT INVENTION EXAMPLES 1 and 2, the shape of the hot-rolled steel sheet was good. Further, the magnetic flux density B50 of the non-oriented electrical steel sheet was also 1.74 T or more, which was a good value. In contrast to this, In COMPARATIVE EXAMPLES 1 and 2, the finishing temperature of the finish rolling exceeded the transformation temperature Arl, so that the magnetic flux density B50 became a low value. Further, in COMPARATIVE EXAMPLES 2 and 3, the outlet side temperature of the third rolling pass exceeded the
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transformation temperature Arl, so that the shape of the hot-rolled steel sheet deteriorated. Further, in COMPARATIVE EXAMPLES 4 and 5, the finishing temperature of the finish rolling fell below the transformation temperature Arl - 50°C, so that the magnetic flux density B50 became a low value. [ Example 2]
[0044] Slabs for non-oriented electrical steel sheets each containing C: 0.003 mass%. Si: 0.5 mass%, Mn: 0.18 mass%, Al: 0.003 mass%, N: 0.0017 mass%, S: 0.0102 mass%, Ti: 0.0030 mass%, Sn: 0.04 mass%, Cu: 0.11 mass%, and P: 0.05 mass%, and a balance being composed of Fe and inevitable impurities were slab heated at 1200°C. Then, rough rolling was performed until the thickness of each of steel sheets became 40 mm. Next, the steel sheets had finish rolling performed thereon through six rolling passes, and had water poured thereonto to be cooled, and then the steel sheets were each coiled at 700 °C. At this time, the thickness of each of hot-rolled steel sheets was 2.4 mm. In Table 3 below, each thickness of the steel sheet obtained after passing through the respective rolling passes in the finish rolling is shown. [0045]
[Table 3]
AFTER AFTER AFTER AFTER AFTER AFTER
FIRST SECOND THIRD FOURTH FIFTH SIXTH
PASS PASS PASS PASS PASS PASS
SHEET
THICKNESS 40 24 14.4 8.6 5.1 3.2 2.4
(mm)
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[0046] Further, in the finish rolling, an outlet side temperature of the third rolling pass, at which the thickness of the steel sheet falls below 12 mm being five times the thickness of the hot-rolled steel sheet, and an outlet side temperature of the sixth rolling pass were changed according samples and the finish rolling was performed. Further, the hot-rolled steel sheets were each coiled, and then whether the coil shape is good or not was also observed. Whether the coil shape of the hot-rolled steel sheet after the finish rolling is good or not was determined by change in sheet thickness and sheet width, the degree of crown and camber, and whether flatness and the like deteriorate or not, similarly to Example 1.
[0047] Thereafter, the obtained hot-rolled steel sheets each had pickling performed thereon and had cold rolling performed thereon, and thereby cold-rolled steel sheets each having a thickness of 0.50 mm were obtained. Next, continuous annealing was performed on the obtained cold-rolled steel sheets at
880°C for 15 seconds, and thereby non-oriented electrical steel sheets were obtained. Then, evaluation of magnetic property of each of the obtained non-oriented electrical steel sheets was conducted. In Table 4 below, a result whether the shape, of the non-oriented electrical steel sheet obtained this time, after the hot rolling being finished is good or not, and a value of the magnetic
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flux density B50 obtained by magnetic measurement being conducted after the continuous annealing are shown. [0048]
[Table 4]
I OUTLET SIDE MAGNETIC ^^J^/^ TRANSFORMATION
SAMPLE TEMPERATURE FINISHING FLUX TEMPERATURE
SAMPLt ftFTER THIRD TEMPERATURE DENSITY , , NOTE
PASS (OC) B50 ^°^^^^ f:for) IT) STEEL (°C)
SHFFT
"^ ^°°0 ~ ^^^ ^--° ^^~ ^^xlMPLE^r
PRESENT
4 895 875 1.76 o INVENTION
EXAMPLE 3
PRESENT
5 880 860 1.75 o INVENTION
EXAMPLE 4
ara o,c 1 -70 COMPARATIVE
__J ^If ^ff '-'^ EXAMPLE 9
7 850 820 1.69 o COMPARATIVE
I I I I I I EXAMPLE 10
[0049] In PRESENT INVENTION EXAMPLES 3 and 4, the shape of the hot-rolled steel sheet was good. Further, the magnetic flux density B50 was also 1.75 T or more, which was a good value. In contrast to this. In COMPARATIVE EXAMPLES 6 and 7, the finishing temperature of the finish rolling exceeded the transformation temperature Arl, so that the magnetic flux density B50 became a low value. Further, in COMPARATIVE EXAMPLES 7 and 8, the outlet side temperature of the third rolling pass exceeded the transformation temperature Arl, so that the shape of the hot-rolled steel sheet deteriorated. Further, in COMPARATIVE EXAMPLES 9 and 10, the finishing temperature of the finish rolling fell below the
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transformation temperature Arl - 50°C, so that the magnetic flux density B50 became a low value.
It should be noted that the above embodiments merely illustrate concrete examples of implementing the present invention, and the technical scope of the present invention is not to be construed in a restrictive manner by these embodiments. That is, the present invention may be implemented in various forms without departing from the technical principles or main features thereof.
INDUSTRIAL APPLICABILITY
[0050] According to the present invention, it is possible to use the excellent non-oriented electrical steel sheet as a core material of a rotary machine and a small-sized transformer.
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CLAIMS [Claim 1] A method of manufacturing a non-oriented electrical steel sheet comprising:
from 11Q0°C to 1250°C, heating a slab that contains C: 0.001 raass% to 0.005 mass%, Si: 0.1 mass% to 2.0 mass%, Al: 0.001 mass% to 1.0 mass%, Mn: 0.1 mass% to 1.0 mass%, S: 0.001 mass% to 0.015 mass%, N: 0.001 mass% to 0.005 mass%, and Ti: 0.0001 mass% to 0.0050 mass%, and a balance being composed of Fe and inevitable impurities and in which when a Si content (mass%), an Al content (mass%), and a Mn content (mass%) are represented as [Si], [Al], and [Mn] respectively, relation of [Si] + 2 x [Al] - [Mn] ^ 2.0 is established;
performing hot rolling of the heated slab and obtaining a hot-rolled steel sheet;
performing cold rolling of the hot-rolled steel sheet and obtaining a cold-rolled steel sheet; and
performing finish annealing of the cold-rolled steel sheet, wherein
in the hot rolling, an outlet side temperature of a rolling pass through which a steel sheet having five times or more thickness of the hot-rolled steel sheet is rolled to five times or less thickness is set to be equal to or lower than a transformation temperature Arl, and a finish temperature of the hot rolling is set to the transformation temperature Arl - 50°C to the transformation temperature Arl. [Claim 2] The method of manufacturing the non-
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^iriented electrical steel sheet according to claim 1, wherein
the slab further contains 0.001 mass% to 0.2 mass% of one type or a plurality of types selected from the group consisting of Sn, Cu, Sb, and Cr. [Claim 3] The method of manufacturing the non-oriented electrical steel sheet according to claim 1 or 2, wherein
the slab further contains 0.001 mass% to 0.1 mass% of one type or a plurality of types selected from the group consisting of P, Ni,.Mo, and V.
Dated this 06/03/2012 f f 1 /
HIUSHIKESlfRAYWAUm^
OF REMFRY &JSAGAR ~ ATTORNEY FOR THE APPLICANTS''
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