METHOD FOR MANUFACTURING NON-ORIENTED ELECTRICAL STEEL SHEET

Abstract

A method for manufacturing a non-oriented electrical steel sheet includes a step of obtaining a hot-rolled steel sheet by performing hot rolling on a steel material having a predetermined chemical composition, a step of performing first cold rolling on the hot-rolled steel sheet, and a step of performing first annealing after the first cold rolling. A final pass of finish rolling is performed in a temperature range equal to or higher than an Ar1 temperature, and cooling of which an average cooling rate is in a range of 50 to 500° C./sec is started in 0.1 sec from completion of rolling of the final pass of the finish rolling and is performed up to a temperature range higher than 250° C. and equal to or lower than 700° C.

Claims

1. A method for manufacturing a non-oriented electrical steel sheet, the method comprising: a step of obtaining a hot-rolled steel sheet by performing hot rolling on a steel material, the steel material having a chemical composition that contains, by mass %, 0.0100% or less of C, 1.50 to 4.00% of Si, 0.0001 to 1.000% of sol.Al, 0.0100% or less of S, 0.0100% or less of N, 2.50 to 5.00% of Mn, Ni, Co, Pt, Pb, Cu, and Au in total, 0.000 to 0.400% of Sn, 0.000 to 0.400% of Sb, 0.000 to 0.400% of P, and 0.0000 to 0.0100% of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd in total with a remainder of Fe and impurities, and satisfies the following Expression (1) in a case where a Mn content is denoted by (Mn), a Ni content is denoted by (Ni), a Co content is denoted by (Co), a Pt content is denoted by (Pt), a Pb content is denoted by (Pb), a Cu content is denoted by (Cu), an Au content is denoted by (Au), a Si content is denoted by (Si), and a sol.Al content is denoted by (sol.Al); a step of performing first cold rolling on the hot-rolled steel sheet; and a step of performing first annealing after the first cold rolling, wherein a final pass of finish rolling during the hot rolling is performed in a temperature range equal to or higher than an Ar1 temperature, and cooling of which an average cooling rate is in a range of 50 to 500° C./sec is started in 0.1 sec from completion of rolling of the final pass of the finish rolling and is performed up to a temperature range higher than 250° C. and equal to or lower than 700° C.,
((Mn)+(Ni)+(Co)+(Pt)+(Pb)+(Cu)+(Au))−((Si)+(sol.Al))>0.000%  (1).

2. The method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the steel material contains one or more selected from the group consisting of, by mass %, 0.020 to 0.400% of Sn, 0.020 to 0.400% of Sb, 0.020 to 0.400% of P, and 0.0005 to 0.0100% of Mg, Ca, Sr, Ba, Ce, La, Nd, Pr, Zn, and Cd in total.

3. The method for manufacturing a non-oriented electrical steel sheet according to claim 1, wherein the first annealing is performed in a temperature range lower than an Ac1 temperature.

4. The method for manufacturing a non-oriented electrical steel sheet according to claim 1, further comprising: a step of performing second cold rolling after the first annealing, wherein cold rolling is performed at a cumulative rolling reduction of 80 to 92% in the step of performing the first cold rolling, and cold rolling is performed at a cumulative rolling reduction of 5 to 25% in the step of performing the second cold rolling.

5. The method for manufacturing a non-oriented electrical steel sheet according to claim 4, further comprising: a step of performing second annealing after the second cold rolling, wherein an annealing temperature is set to be lower than an Ac1 temperature in the second annealing.

6. The method for manufacturing a non-oriented electrical steel sheet according to claim 2, wherein the first annealing is performed in a temperature range lower than an Ac1 temperature.

7. The method for manufacturing a non-oriented electrical steel sheet according to claim 2, further comprising: a step of performing second cold rolling after the first annealing, wherein cold rolling is performed at a cumulative rolling reduction of 80 to 92% in the step of performing the first cold rolling, and cold rolling is performed at a cumulative rolling reduction of 5 to 25% in the step of performing the second cold rolling.

8. The method for manufacturing a non-oriented electrical steel sheet according to claim 3, further comprising: a step of performing second cold rolling after the first annealing, wherein cold rolling is performed at a cumulative rolling reduction of 80 to 92% in the step of performing the first cold rolling, and cold rolling is performed at a cumulative rolling reduction of 5 to 25% in the step of performing the second cold rolling.

9. The method for manufacturing a non-oriented electrical steel sheet according to claim 6, further comprising: a step of performing second cold rolling after the first annealing, wherein cold rolling is performed at a cumulative rolling reduction of 80 to 92% in the step of performing the first cold rolling, and cold rolling is performed at a cumulative rolling reduction of 5 to 25% in the step of performing the second cold rolling.

10. The method for manufacturing a non-oriented electrical steel sheet according to claim 7, further comprising: a step of performing second annealing after the second cold rolling, wherein an annealing temperature is set to be lower than an Ac1 temperature in the second annealing.

11. The method for manufacturing a non-oriented electrical steel sheet according to claim 8, further comprising: a step of performing second annealing after the second cold rolling, wherein an annealing temperature is set to be lower than an Ac1 temperature in the second annealing.

12. The method for manufacturing a non-oriented electrical steel sheet according to claim 9, further comprising: a step of performing second annealing after the second cold rolling, wherein an annealing temperature is set to be lower than an Ac1 temperature in the second annealing.

Description

EXAMPLES

[0098] Next, the method for manufacturing a non-oriented electrical steel sheet according to the embodiment of the invention will be specifically described with reference to examples. Examples to be described below are merely examples of the method for manufacturing a non-oriented electrical steel sheet according to the embodiment of the invention, and the method for manufacturing a non-oriented electrical steel sheet according to the embodiment of the invention is not limited to the following examples.

First Example

[0099] Molten steel was casted to produce slabs having chemical compositions shown in Table 1 to be described below. The left side of Expression shown in Table 1 represents the value of the left side of Expression (1) having been described above. After that, the produced slabs were heated up to 1150° C. and were subjected to hot rolling under conditions shown in Table 2, so that hot-rolled steel sheets having a sheet thickness of 2.5 mm were obtained. Water cooling was performed after finish rolling, and the steel sheets were wound after the water cooling was stopped at winding temperatures shown in Table 2.

[0100] The exit-side temperature (finishing temperature) of the final pass of the finish rolling, the time from the completion of the rolling of the final pass of the finish rolling to the start of cooling (the start of water cooling), an average cooling rate, and a winding temperature are shown in Table 2. A distance from a finishing mill to the start of water cooling and a sheet threading speed in that section were measured and “sheet threading distance/sheet threading speed” was calculated to obtain the time from the completion of the rolling of the final pass of the finish rolling to the start of cooling. Here, a fact that the time from the completion of the rolling of the final pass of the finish rolling to the start of cooling was 0.0 sec means that cooling was performed so that cooling water was applied to the exit side of the final pass of the finishing mill.

[0101] Then, pickling was performed on the obtained hot-rolled steel sheets to remove scale. After that, cold rolling was performed at a cumulative rolling reduction of 85% until a sheet thickness reached 0.385 mm, so that steel sheets (cold-rolled steel sheets) were obtained. First annealing (process annealing) for heating the obtained steel sheets and holding the steel sheets for 5 to 60 sec at 700° C. which was a temperature lower than the Ac1 temperatures of all the steel sheets, in a non-oxidizing atmosphere was performed. Then, second cold rolling (skin pass rolling) was performed at a cumulative rolling reduction of 9% until a sheet thickness reached 0.35 mm.

[0102] The Ar1 temperature was obtained from a change in the thermal expansion of the steel sheet that was being cooled at an average cooling rate of 1° C./sec, and the Ac1 temperature was obtained from a change in the thermal expansion of the steel sheet that was being heated at an average heating rate of 1° C./sec.

[0103] After the second cold rolling (skin pass rolling) was performed, second annealing (stress relief annealing) for heating the steel sheets for 2 hours at 800° C. was performed. 800° C. was a temperature lower than the Ac1 temperatures of all the steel sheets.

[0104] After the second annealing was performed, magnetic flux densities B50 were measured using a single-sheet magnetic measurement device. Samples of 55 mm square were taken in two directions that were inclined with respect to the rolling directions of the steel sheets by 0° and 45°, and magnetic flux densities B50 were measured. The magnetic flux density in the direction inclined with respect to the rolling direction by 45° was referred to as the magnetic flux density B50 in a 450 direction. The whole circumferential average of the magnetic flux densities B50 was obtained from the calculation of an average value of the magnetic flux densities in directions inclined with respect to the rolling direction by 0°, 45°, 90°, and 135°.

[0105] Further, energy losses (W/kg) of the samples, which were obtained from the non-oriented electrical steel sheets, on the whole circumferential average, which were generated in a case where an AC magnetic field having a frequency of 400 Hz was applied so that the maximum magnetic flux density was 1.0 T, were measured, so that iron losses W10/400 were obtained.

TABLE-US-00001 TABLE 1 Chemical composition (mass %) Remainder iron and impurities Left side of No. C Si sol-Al S N Mn Ni Co Pt Pb Cu Au Expression 101 0.0009 2.50 0.012 0.0023 0.0024 3.07 — — — — — — 0.55 102 0.0014 2.50 0.009 0.0020 0.0023 — 3.11 — — — — — 0.59 103 0.0011 2.52 0.012 0.0023 0.0020 — — 3.08 — — — — 0.54 104 0.0012 2.53 0.008 0.0024 0.0017 — — — 3.10 — — — 0.57 105 0.0009 2.52 0.008 0.0019 0.0022 — — — — 3.10 — — 0.58 106 0.0011 2.49 0.010 0.0021 0.0023 — — — — — 3.12 — 0.62 107 0.0007 2.50 0.007 0.0022 0.0023 — — — — — — 3.06 0.55 108 0.0009 2.50 0.013 0.0020 0.0018 3.10 — — — — — — 0.59 109 0.0006 2.50 0.010 0.0018 0.0018 3.09 — — — — — — 0.59 110 0.0012 2.47 0.009 0.0020 0.0023 3.10 — — — — — — 0.62 111 0.0013 2.49 0.012 0.0020 0.0018 3.11 — — — — — — 0.60 112 0.0010 2.48 0.009 0.0016 0.0016 3.11 — — — — — — 0.62 113 0.0010 2.49 0.010 0.0017 0.0024 3.11 — — — — — — 0.61 114 0.0006 2.48 0.012 0.0018 0.0018 3.11 — — — — — — 0.61 115 0.0009 2.51 0.012 0.0024 0.0021 3.08 — — — — — — 0.56 116 0.0011 2.50 0.321 0.0020 0.0024 3.42 — — — — — — 0.59 117 0.0012 2.51 0.612 0.0021 0.0023 3.73 — — — — — — 0.61 118 0.0012 2.50 0.010 0.0019 0.0023 3.10 — — — — — — 0.59 119 0.0011 2.51 0.011 0.0022 0.0021 3.11 — — — — — — 0.59

TABLE-US-00002 TABLE 2 Hot rolling conditions Time from Magnetic characteristics after annealing finishing Average performed for 2 hours at 800° C. Finishing to start of cooling Winding B50 in 45° B50 on whole temperature Ar1 cooling rate temperature direction circumferential W10/400 No. (° C.) (° C.) (s) (° C./s) (° C.) (T) average (T) (W/kg) Note 101 800 780 0.0 100 500 1.827 1.704 15.22 Example of invention 102 800 780 0.0 100 500 1.831 1.701 14.90 Example of invention 103 800 780 0.0 100 500 1.833 1.696 14.96 Example of invention 104 800 780 0.0 100 500 1.834 1.702 14.92 Example of invention 105 800 780 0.0 100 500 1.829 1.697 15.18 Example of invention 106 800 780 0.0 100 500 1.832 1.702 15.12 Example of invention 107 800 780 0.0 100 500 1.832 1.697 15.16 Example of invention 108 800 780  0.07 100 500 1.822 1.693 15.14 Example of invention 109 800 780 0.3 100 500 1.811 1.680 16.03 Comparative Example 110 800 780 0.6 100 500 1.812 1.677 16.40 Comparative Example 111 800 780 1.0 100 500 1.808 1.681 16.28 Comparative Example 112 800 780 0.0  50 500 1.819 1.689 15.29 Example of invention 113 800 780 0.0  30 500 1.810 1.684 16.10 Comparative Example 114 800 780 0.0 200 500 1.830 1.703 15.20 Example of invention 115 800 780 0.0 100 240 1.813 1.679 16.03 Comparative Example 116 800 780 0.0 100 500 1.825 1.691 14.64 Example of invention 117 800 780 0:0 100 500 1.818 1.688 14.11 Example of invention 118 800 780 0.0 100 400 1.826 1.694 15.32 Example of invention 119 800 780 0.0 100 650 1.827 1.693 15.34 Example of invention

[0106] Underlines shown in Table 2 represent conditions out of the scope of the invention. Magnetic characteristics excellent both in the 45° direction and on the whole circumferential average (high magnetic flux densities B50 and low iron losses W10/400) were obtained from Nos. 101 to 108, Nos. 112 and 114, and Nos. 116 to 119 that were the examples of the invention.

[0107] On the other hand, since Nos. 109 to 111, which were comparative examples, had a long time from the completion of the rolling of the final pass of the finish rolling to the start of cooling (“the time from the finishing to the start of cooling” in Table 1). Nos. 109 to 111 had low magnetic flux densities B50 and high iron losses W10/400. As a result, the magnetic characteristics of Nos. 109 to 111 were poorer than those of the examples of the invention. Since No. 113, which was a comparative example, had a low average cooling rate, No. 113 had a magnetic flux density B50 lower than the magnetic flux densities B50 of the examples of the invention and an iron loss W10/400 higher than the iron losses W10/400 of the examples of the invention. As a result, the magnetic characteristics of No. 113 were poorer than those of the examples of the invention. Since No. 115, which was a comparative example, had a low winding temperature (a temperature at which cooling was to be stopped), No. 115 had a magnetic flux density B50 lower than the magnetic flux densities B50 of the examples of the invention and an iron loss W10/400 higher than the iron losses W10/400 of the examples of the invention. As a result, the magnetic characteristics of No. 115 were poorer than those of the examples of the invention.

Second Example

[0108] Molten steel was casted to produce slabs having chemical compositions shown in Table 3 to be described below. After that, the produced ingots were heated up to 1150° C. and were subjected to hot rolling under conditions shown in Table 4, so that hot-rolled steel sheets having a sheet thickness of 2.5 mm were obtained. Water cooling was performed after finish rolling, and the steel sheets were wound after the water cooling was stopped at winding temperatures shown in Table 2.

[0109] Since items shown in Table 4 are the same as those described in Example 1, the description thereof will be omitted.

[0110] Then, pickling was performed on the obtained hot-rolled steel sheets to remove scale. After that, cold rolling was performed at a cumulative rolling reduction of 85% until a sheet thickness reached 0.385 mm, so that steel sheets (cold-rolled steel sheets) were obtained. First annealing (process annealing) for heating the obtained steel sheets and holding the steel sheets for 5 to 60 sec at 700° C., which was a temperature lower than the Ac1 temperatures of all the steel sheets, in a non-oxidizing atmosphere was performed. Then, second cold rolling (skin pass rolling) was performed at a cumulative rolling reduction of 9% until a sheet thickness reached 0.35 mm.

[0111] After the second cold rolling (skin pass rolling) was performed, second annealing (stress relief annealing) for heating the steel sheets for 2 hours at 800° C. was performed. 800° C. was a temperature lower than the Ac1 temperatures of all the steel sheets.

[0112] After the second annealing was performed, magnetic flux densities B50 and iron losses W10/400 were measured using a single-sheet magnetic measurement device. The measurement was performed in the same procedure as in the first example. Further, the Ar1 temperatures and the Ac1 temperatures were measured by the same methods as in the first example.

TABLE-US-00003 TABLE 3 Chemical composition (mass %) Remainder iron and impurities No. C Si sol-Al S N Mn Sn Sb P Mg Ca Sr 201 0.0010 2.52 0.007 0.0019 0.0016 3.11 — — — — — — 202 0.0007 2.49 0.012 0.0024 0.0018 3.14 0.051 — — — — — 203 0.0012 2.51 0.013 0.0021 0.0022 3.09 — 0.053 — — — — 204 0.0009 2.52 0.013 0.0023 0.0019 3.12 — — 0.049 — — — 205 0.0010 2.53 0.013 0.0017 0.0022 3.13 — — — 0.0051 — — 206 0.0009 2.52 0.011 0.0017 0.0018 3.11 — — — — 0.0047 — 207 0.0014 2.54 0.011 0.0023 0.0020 3.12 — — — — — 0.0047 208 0.0013 2.53 0.007 0.0022 0.0021 3.11 — — — — — — 209 0.0007 2.46 0.007 0.0020 0.0017 3.13 — — — — — — 210 0.0013 2.50 0.011 0.0023 0.0019 3.12 — — — — — — 211 0.0011 2.48 0.013 0.0017 0.0019 3.08 — — — — — — 212 0.0014 2.46 0.007 0.0016 0.0022 3.12 — — — — — — 213 0.0011 2.48 0.012 0.0019 0.0017 3.13 — — — — — — 214 0.0008 2.54 0.008 0.0023 0.0023 3.11 — — — — — — 213 0.0008 2.49 0.320 0.0020 0.0018 3.43 0.049 — — — — — 216 0.0010 2.50 0.610 0.0023 0.0019 3.71 0.051 — — — — — Chemical composition (mass %) Remainder iron and impurities Left side of No. Ba Ce La Nd Pr Zn Cd Expression 201 — — — — — — — 0.58 202 — — — — — — — 0.64 203 — — — — — — — 0.57 204 — — — — — — — 0.59 205 — — — — — — — 0.59 206 — — — — — — — 0.58 207 — — — — — — — 0.57 208 0.0052 — — — — — — 0.58 209 — 0.0051 — — — — — 0.67 210 — — 0.0053 — — — — 0.60 211 — — — 0.0051 — — — 0.58 212 — — — — 0.0053 — — 0.64 213 — — — — — 0.0049 — 0.64 214 — — — — — — 0.0051 0.57 213 — — — — — — — 0.62 216 — — — — — — — 0.60

TABLE-US-00004 TABLE 4 Hot rolling conditions Time from Magnetic characteristics after annealing finishing to Average performed for 2 hours at 800° C. Finishing start of cooling Winding B50 in 45° B50 on whole temperature Ar1 cooling rate temperature direction circumferential W10/400 No. (° C.) (° C.) (s) (° C./s) (° C.) (T) average (T) (W/kg) Note 201 800 780 0.0 100 500 1.830 1.699 15.13 Example of invention 202 800 780 0.0 100 500 1.836 1.710 15.11 Example of invention 203 800 780 0.0 100 500 1.842 1.707 15.09 Example of invention 204 800 780 0.0 100 500 1.841 1.709 15.07 Example of invention 205 800 780 0.0 100 500 1.833 1.696 14.74 Example of invention 206 800 780 0.0 100 500 1.827 1.704 14.70 Example of invention 207 800 780 0.0 100 500 1.826 1.701 14.69 Example of invention 208 800 780 0.0 100 500 1.827 1.696 14.71 Example of invention 209 800 780 0.0 100 500 1.831 1.703 14.69 Example of invention 210 800 780 0.0 100 500 1.826 1.703 14.69 Example of invention 211 800 780 0.0 100 500 1.826 1.704 14.70 Example of invention 212 800 780 0.0 100 500 1.829 1.699 14.72 Example of invention 213 800 780 0.0 100 500 1.827 1.697 14.68 Example of invention 214 800 780 0.0 100 500 1.833 1.696 14.70 Example of invention 215 800 780 0.0 100 500 1.829 1.705 14.62 Example of invention 216 800 780 0.0 100 500 1.821 1.691 14.22 Example of invention

[0113] Nos. 201 to 216 were examples of the invention, and all of them had good magnetic characteristics. In particular, the magnetic flux densities B50 of Nos. 202 to 204 were higher than those of No. 201 and Nos. 205 to 214, and the iron losses W10/400 of Nos. 205 to 214 were lower than those of Nos. 201 to 204. The iron losses W10/400 of Nos. 215 and 216 having high sol.Al contents were lower than that of No. 201, and the magnetic flux densities B50 of Nos. 215 and 216 were lower than that of No. 201.

Third Example

[0114] Molten steel was casted to produce slabs having chemical compositions shown in Table 5 to be described below. After that, the produced ingots were heated up to 1150° C. and were subjected to hot rolling under conditions shown in Table 6, so that hot-rolled steel sheets having a sheet thickness of 2.5 mm were obtained. Water cooling was performed after finish rolling, and the steel sheets were wound after the water cooling was stopped at winding temperatures shown in Table 6.

[0115] Since items shown in Table 6 are the same as those described in Example 1, the description thereof will be omitted.

[0116] Then, pickling was performed on the obtained hot-rolled steel sheets to remove scale. After that, cold rolling was performed at a cumulative rolling reduction of 85% until a sheet thickness reached 0.385 mm, so that steel sheets (cold-rolled steel sheets) were obtained. First annealing (process annealing) for heating the obtained steel sheets and holding the steel sheets for 5 to 60 sec at 700° C., which was a temperature lower than the Ac1 temperatures of all the steel sheets, in a non-oxidizing atmosphere was performed.

[0117] After the first annealing was performed, magnetic flux densities B50 and iron losses W10/400 were measured using a single-sheet magnetic measurement device. The measurement was performed in the same procedure as in the first example. Further, the Ar1 temperatures and the Ac1 temperatures were measured by the same methods as in the first example.

TABLE-US-00005 TABLE 5 Chemical composition (mass %) Remainder iron and impurities Left side of No. C Si sol-Al S N Mn Ni Co Pt Pb Cu Au Others Expressions 301 0.0009 2.51 0.012 0.0019 0.0021 3.10 — — — — — — — 0.55 302 0.0009 2.51 0.009 0.0019 0.0022 — 3.11 — — — — — — 0.59 303 0.0009 2.49 0.011 0.0022 0.0022 — — 3.11 — — — — — 0.54 304 0.0008 2.50 0.011 0.0021 0.0021 — — — 3.10 — — — — 0.57 305 0.0011 2.50 0.012 0.0020 0.0018 — — — — 3.10 — — — 0.58 306 0.0011 2.50 0.010 0.0021 0.0020 — — — — — 3.09 — — 0.62 307 0.0009 2.49 0.011 0.0018 0.0018 — — — — — — 3.08 — 0.55 308 0.0010 2.51 0.012 0.0020 0.0020 3.12 — — — — — — — 0.59 309 0.0010 2.51 0.011 0.0020 0.0020 3.11 — — — — — — — 0.59 310 0.0011 2.50 0.012 0.0021 0.0018 3.10 — — — — — — — 0.62 311 0.0009 2.50 0.010 0.0019 0.0018 3.10 — — — — — — — 0.60 312 0.0009 2.51 0.011 0.0019 0.0020 3.08 — — — — — — — 0.62 313 0.0012 2.49 0.011 0.0021 0.0018 3.10 — — — — — — — 0.61 314 0.0012 2.51 0.008 0.0018 0.0019 3.09 — — — — — — — 0.61 315 0.0011 2.51 0.010 0.0020 0.0018 3.08 — — — — — — — 0.56 316 0.0008 2.50 0.322 0.0019 0.0019 3.31 — — — — — — — 0.59 317 0.0008 2.50 0.609 0.0020 0.0018 3.71 — — — — — — — 0.59 318 0.0011 2.49 0.011 0.0019 0.0021 3.10 — — — — — — Sn: 0.05 0.59 319 0.0010 2.49 0.009 0.0018 0.0020 3.09 — — — — — — Sb: 0.05 0.59 320 0.0011 2.48 0.011 0.0021 0.0021 3.09 — — — — — — P: 0.05 0.59 321 0.0009 2.52 0.011 0.0021 0.0021 3.11 — — — — — — Mg: 0.005 0.59 322 0.0011 2.50 0.009 0.0018 0.0019 3.11 — — — — — — Ca: 0.005 0.59 323 0.0011 2.49 0.010 0.0020 0.0021 3.10 — — — — — — Ba: 0.005 0.59 324 0.0008 2.52 0.009 0.0022 0.0020 3.11 — — — — — — Ce: 0.005 0.59 325 0.0011 2.51 0.012 0.0019 0.0019 3.09 — — — — — — La: 0.005 0.59 326 0.0010 2.48 0.010 0.0022 0.0018 3.12 — — — — — — Nd: 0.005 0.59

TABLE-US-00006 TABLE 6 Hot rolling conditions Time from finishing to Average Magnetic characteristics Finishing start of cooling Winding B50 in 45° B50 on whole temperature Ar1 cooling rate temperature direction circumferential W10/400 No. (° C.) (° C.) (s) (° C./s) (° C.) (T) average (T) (W/kg) Note 301 800 780 0.0 100 500 1.671 1.617 18.19 Example of invention 302 800 780 0.0 100 500 1.671 1.622 18.23 Example of invention 303 800 780 0.0 100 500 1.672 1.621 18.17 Example of invention 304 800 780 0.0 100 500 1.671 1.622 18.24 Example of invention 305 800 780 0.0 100 500 1.673 1.622 18.20 Example of invention 306 800 780 0.0 100 500 1.669 1.616 18.22 Example of invention 307 800 780 0.0 100 500 1.672 1.622 18.22 Example of invention 308 800 780  0.07 100 500 1.661 1.608 18.62 Example of invention 309 800 780 0.3 100 500 1.653 1.604 19.49 Comparative Example 310 800 780 0.6 100 500 1.648 1.597 19.53 Comparative Example 311 800 780 1.0 100 500 1.654 1.597 19.49 Comparative Example 312 800 780 0.0 50 500 1.662 1.608 18.62 Example of invention 313 800 780 0.0 30 500 1.651 1.604 19.48 Comparative Example 314 800 780 0.0 200 500 1.671 1.618 18.22 Example of invention 315 800 780 0.0 100 240 1.651 1.600 19.50 Comparative Example 316 800 780  0.07 100 500 1.667 1.618 18.22 Example of invention 317 800 780  0.07 100 500 1.668 1.622 18.23 Example of invention 318 800 780  0.07 100 500 1.679 1.631 18.24 Example of invention 319 800 780  0.07 100 500 1.676 1.627 18.17 Example of invention 320 800 780  0.07 100 400 1.672 1.631 18.32 Example of invention 321 800 780  0.07 100 500 1.666 1.623 17.20 Example of invention 322 800 780  0.07 100 600 1.661 1.617 17.34 Example of invention 323 800 780  0.07 100 500 1.666 1.617 17.16 Example of invention 324 800 780  0.07 100 500 1.669 1.621 17.17 Example of invention 325 800 780  0.07 100 500 1.669 1.622 17.19 Example of invention 326 800 780  0.07 100 500 1.673 1.624 17.24 Example of invention

[0118] Underlines shown in Table 6 represent conditions out of the scope of the invention. Magnetic characteristics excellent both in the 45° direction and on the whole circumferential average (high magnetic flux densities B50 and low iron losses W10/400) were obtained from Nos. 301 to 308, Nos. 312 and 314, and Nos. 316 to 326 that were the examples of the invention.

[0119] On the other hand, since Nos. 309 to 311, which were comparative examples, had a long time from the completion of the rolling of the final pass of the finish rolling to the start of cooling, Nos. 309 to 311 had low magnetic flux densities B50 and high iron losses W10/400. As a result, the magnetic characteristics of Nos. 309 to 311 were poorer than those of the examples of the invention. Since No. 313, which was a comparative example, had a low average cooling rate, No. 313 had a magnetic flux density B50 lower than the magnetic flux densities B50 of the examples of the invention and an iron loss W10/400 higher than the iron losses W10/400 of the examples of the invention. As a result, the magnetic characteristics of No. 313 were poorer than those of the examples of the invention. Since No. 315, which was a comparative example, had a low winding temperature, No. 315 had a magnetic flux density B50 lower than the magnetic flux densities B50 of the examples of the invention and an iron loss W10/400 higher than the iron losses W10/400 of the examples of the invention. As a result, the magnetic characteristics of No. 315 were poorer than those of the examples of the invention.