ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Abstract

This electrical steel sheet contains, as a chemical composition, by mass %, C: 0.0035% or less, Si: 2.00% to 3.50%, Mn: 2.00% to 5.00%, P: 0.050% or less, S: 0.0070% or less, Al: 0.15% or less, N: 0.0030% or less, Ni: 0% to 1.00%, Cu: 0% to 0.10%, and a remainder: Fe and impurities, in which an X-ray random intensity ratio in a {100} <011> crystal orientation on a sheet surface is 15.0 to 50.0, and magnetic flux densities in 0°, 22.5°, and 45° directions from a rolling direction each satisfy [1.005×(B.sub.50 (0°)+B.sub.50 (45°))/2≥B.sub.50 (22.5°)].

Claims

1. An electrical steel sheet comprising, as a chemical composition, by mass %: C: 0.0035% or less, Si: 2.00% to 3.50%, Mn: 2.00% to 5.00%, P: 0.050% or less, S: 0.0070% or less, Al: 0.15% or less, N: 0.0030% or less, Ni: 0% to 1.00%, Cu: 0% to 0.10%, and a remainder: Fe and impurities, an X-ray random intensity ratio in a {100} <011> crystal orientation on a sheet surface is 15.0 to 50.0, and magnetic flux densities in 0°, 22.5°, and 45° directions from a rolling direction each satisfy Expression (i),
1.005×(B.sub.50 (0°)+B.sub.50 (45°))/2≤B.sub.50 (22.5°)  (i) here, the meaning of each symbol in Expression (i) is as follows: B.sub.50 (0°): a magnetic flux density (T) in the 0° direction from the rolling direction, B.sub.50 (22.5°): a magnetic flux density (T) in the 22.5° direction from the rolling direction, and B.sub.50 (45°): a magnetic flux density (T) in the 45° direction from the rolling direction.

2. The electrical steel sheet according to claim 1, wherein a sheet thickness is 0.25 to 0.50 mm.

3. A method for manufacturing an electrical steel sheet, the method comprising in the following order: on a slab having a chemical composition of, by mass %: C: 0.0035% or less, Si: 2.00% to 3.50%, Mn: 2.00% to 5.00%, P: 0.050% or less, S: 0.0070% or less, Al: 0.15% or less, N: 0.0030% or less, Ni: 0% to 1.00%, Cu: 0% to 0.10%, and a remainder: Fe and impurities, (a) heating the slab to 1000° C. to 1200° C., then, performing hot rolling under a condition where a final rolling temperature is within a temperature range of an Ac.sub.3 transformation point or higher, and cooling the slab to a temperature of 600° C. or lower after completion of the hot rolling to 600° C. such that an average cooling rate reaches 50 to 150° C./s, (b) performing first cold rolling at a rolling reduction of 80% to 92% without performing an annealing treatment, (c) performing an intermediate annealing treatment at an intermediate annealing temperature within a range of 500° C. or higher and lower than an Ac.sub.1 transformation point, (d) performing second cold rolling at a rolling reduction of more than 15.0% and 20.0% or less, and (e) performing a final annealing treatment at a final annealing temperature within a range of 500° C. or higher and lower than the Ac.sub.1 transformation point.

4. The method for manufacturing an electrical steel sheet according to claim 3, wherein, in the final annealing treatment, a temperature rising rate up to the final annealing temperature is set to 0.1° C./s or faster and slower than 10.0° C./s, and a retention time at the final annealing temperature is set to 10 to 120 s.

Description

EXAMPLES

[0142] Slabs having a chemical composition in Table 1 were heated to 1150° C. and then hot-rolled under conditions shown in Table 2 to manufacture hot-rolled steel sheets having a sheet thickness of 2.0 mm.

TABLE-US-00001 TABLE 1 Steel Chemical composition (mass %, remainder: Fe and impurity) Ac.sub.1 point Ac.sub.3 point type C Si Mn P S Al N Ni Cu (° C.) (° C.) A 0.0015 2.47 3.06 0.018 0.0022 0.05 0.0018 0.0009 0.0022 878 896 B 0.0018 3.12 3.76 0.011 0.0016 0.02 0.0008 0.0018 0.0016 894 916 C 0.0016 2.38 4.17 0.009 0.0025 0.01 0.0010 0.0011 0.0057 806 861 D 0.0015 2.11 2.57 0.010 0.0021 0.03 0.0016 0.0063 0.0014 903 924 E 0.0012 2.84 3.49 0.008 0.0026 0.02 0.0019 0.2380 0.0019 885 900 F 0.0017 2.09 3.05 0.009 0.0011 0.04 0.0012 0.0024 0.0750 912 933 G 0.0018 2.62 3.28 0.010 0.0015 0.01 0.0010 0.0510 0.0660 842 905 H 0.0015 3.30 3.05 0.027 0.0037 0.08 0.0022 0.8400 0.0057 945 1003 I 0.0013 2.74 3.71 0.013 0.0019 0.05 0.0015 0.0055 0.0130 876 935 J 0.0018 2.42 1.83 0.010 0.0022 0.01 0.0011 0.0016 0.0026 923 941 K 0.0017 2.18 5.21 0.009 0.0028 0.03 0.0008 0.0021 0.0030 754 807 L 0.0015 1.89 2.74 0.017 0.0025 0.02 0.0012 0.0013 0.0041 865 878 M 0.0016 3.66 2.81 0.011 0.0026 0.03 0.0012 0.0008 0.0010 — — N 0.0032 3.22 2.95 0.025 0.0018 0.08 0.0017 0.0012 0.0018 973 996 O 0.0018 2.94 4.82 0.019 0.0009 0.04 0.0013 0.0009 0.0019 761 815 P 0.0014 2.68 3.45 0.017 0.0012 0.14 0.0019 0.0004 0.0005 804 872

TABLE-US-00002 TABLE 2 First Second cold Intermediate cold Final Hot rolling step rolling annealing rolling annealing Final step step step step rolling Cooling Rolling Annealing Rolling Annealing Test Steel temperature Ac.sub.3 rate Annealing reduction temperature reduction temperature No. type (° C.) (° C.) (° C./s) step (%) (° C.) (%) (° C.) Note 1 A 923 896 85 Absent 85.0 700 18.0 850 Present 2 B 947 916 86 Absent 85.0 700 18.0 850 Invention 3 C 928 861 92 Absent 85.0 700 18.0 780 Example 4 D 951 924 88 Absent 83.0 700 18.0 880 5 E 934 900 89 Absent 83.0 650 20.0 800 6 F 987 933 91 Absent 83.0 650 20.0 880 7 G 952 905 112 Absent 80.0 650 20.0 800 8 H 1023 1003  124 Absent 80.0 650 20.0 880 9 I 985 935 108 Absent 80.0 800 17.0 780 10 C 908 861 117 Absent 87.0 800 17.0 780 11 D 971 924 120 Absent 87.0 800 17.0 850 12 J 969 941 114 Absent 87.0 800 17.0 850 Comparative 13 K 853 807 109 Absent — — — — Example 14 L 907 878 68 Absent 85.0 550 17.0 825 15 M 931 — 68 Absent 85.0 550 17.0 880 16 A 862 896 61 Absent 80.0 550 17.0 825 17 B 962 916 39 Absent 80.0 550 17.0 825 18 A 927 896 161 Absent 80.0 850 16.0 825 19 B 948 916 124 Absent 78.0 850 16.0 825 20 A 936 896 118 Absent 94.0 850 16.0 825 21 B 958 916 114 Absent 83.0 450 16.0 825 22 A 933 896 114 Absent 83.0 900 16.0 825 23 B 961 916 117 Absent 83.0 825 14.0 825 24 B 946 896 135 Absent 85   825 22.0 825 25 A 944 896 112 Absent 90.0 825 19.0 480 26 B 957 916 111 Absent 90.0 825 19.0 925 27 A 939 896 116 Present — — — — 28 N 1012 996 78 Absent 87.0 750 18.0 750 Present 29 O 862 815 96 Absent 87.0 750 18.0 750 Invention 30 P 908 872 84 Absent 87.0 750 18.0 750 Example

[0143] [Evaluation Tests]

[0144] The following evaluation tests were performed on an electrical steel sheet of each steel number.

[0145] [Test for Measuring X-Ray Random Intensity in {100} <110> Crystal Orientation]

[0146] A sample was taken from the steel sheet of each test number, and the surface was mirror-polished. From the mirror-polished region, an optional region where the measurement intervals of pixels were ⅕ or less of the average grain diameter and 5000 or more crystal grains could be measured was selected. An EBSD measurement was performed in the selected region to obtain the pole figures of {200}, {110}, {310}, and {211}. An ODF distribution representing a three-dimensional texture that was calculated by the series expansion method was obtained using these pole figures. From the obtained ODF, the X-ray random intensity ratio in the {100} <011> crystal orientation was obtained.

[0147] [Test for Measuring Magnetic Flux Density]

[0148] A 55 mm×55 mm single sheet test piece was produced from the electrical steel sheet of each test number by punching. The magnetic flux densities B.sub.50 (0°), B.sub.50 (22.5°), and B.sub.50 (45°) in 0°, 22.5°, and 45° directions from a rolling direction RD were each measured by the above-described method using a single sheet magnetic measuring instrument. The magnetic field during the measurement was set to 5000 A/m.

[0149] [Iron Loss at 1000 Hz W.sub.10/1000]

[0150] A 55 mm×55 mm single sheet test piece was produced from the electrical steel sheet of each test number by punching. The iron loss W.sub.10/1000 (W/kg) of the single sheet test piece magnetized at a frequency of 1000 Hz and a maximum magnetic flux density of 1.0 T was measured using the single sheet magnetic measuring instrument.

[0151] [Evaluation Results]

[0152] The evaluation results are summarized in Table 3. It should be noted that, as a result of measuring the chemical compositions of the manufactured electrical steel sheets, it was found that the electrical steel sheet of each steel number had the same chemical composition as the chemical composition shown in Table 1.

TABLE-US-00003 TABLE 3 {100} <110> integration degree Magnetic flux density X-ray random Value of Whether or Iron loss Test Steel intensity B.sub.50 (0°) B.sub.50 (22.5°) B.sub.50 (45°) left side not satisfying W.sub.10/1000 No. type ratio (T) (T) (T) of Expression (i)* Expression (i) (W/kg) Note 1 A 31 1.594 1.728 1.826 1.719 OK 42 Present 2 B 36 1.590 1.727 1.836 1.722 OK 41 Invention 3 C 28 1.590 1.719 1.829 1.718 OK 40 Example 4 D 33 1.577 1.716 1.813 1.703 OK 45 5 E 31 1.576 1.718 1.816 1.704 OK 48 6 F 25 1.579 1.711 1.814 1.705 OK 41 7 G 27 1.568 1.720 1.843 1.714 OK 46 8 H 46 1.566 1.691 1.766 1.674 OK 42 9 I 38 1.603 1.715 1.801 1.711 OK 43 10 C 32 1.594 1.721 1.824 1.718 OK 48 11 D 26 1.606 1.729 1.831 1.727 OK 49 12 J 11 1.623 1.650 1.671 1.655 NG 59 Comparative 13 K — — — — — NG — Example 14 E 6 1.624 1.647 1.673 1.657 NG 60 15 M 10 1.630 1.649 1.680 1.663 NG 48 16 A 6 1.625 1.670 1.701 1.671 NG 56 17 B 7 1.631 1.653 1.686 1.667 NG 66 18 A 6 1.624 1.671 1.700 1.670 OK 58 19 B 6 1.587 1.634 1.669 1.636 NG 62 20 A 11 1.573 1.658 1.729 1.659 NG 66 21 B 7 1.623 1.665 1.710 1.675 NG 59 22 A 8 1.635 1.664 1.688 1.670 NG 60 23 B 38 1.618 1.705 1.809 1.722 NG 47 24 B 12 1.627 1.652 1.678 1.661 NG 48 25 A 25 1.602 1.664 1.811 1.715 NG 73 26 B 4 1.626 1.658 1.683 1.663 NG 60 27 A — — — — — NG — 28 N 46 1.541 1.788 1.819 1.688 OK 42 Present 29 O 23 1.552 1.756 1.800 1.684 OK 41 Invention 30 P 39 1.560 1.722 1.783 1.680 OK 43 Example *1.005 × (B.sub.50 (0°) + B.sub.50 (45°))/2 ≤ B.sub.50 (22.5°) . . . (i)

[0153] As shown in Table 3, in Test Nos. 1 to 11 and 28 to 30 that satisfied the specifications of the present invention, it was found that the iron losses and the magnetic flux densities were excellent. In addition, the results show that the magnetic characteristics were excellent not only in the {100} <011> crystal orientation but also in the periphery thereof.

[0154] In contrast, since the Mn content was less than the specified value in Test No. 12, and the Si content was less than the specified value in Test No. 14, the {100} <011> crystal orientation did not develop. Since the Mn content was excessive in Test No. 13, the workability deteriorated and cracks were generated after cold rolling, which stopped the experiment. In addition, since the Si content was excessive and deviated from the chemical composition of the α-γ transformation system in Test No. 15, the {100} <011> crystal orientation did not develop.

[0155] Since the final rolling temperature was low in Test No. 16, the cooling rate was too slow in Test No. 17, and the cooling rate was too fast in Test No. 18, the {100} <011> crystal orientation did not develop. Since the first cold rolling ratio was too low in Test No. 19, and, conversely, the first cold rolling ratio was too high in Test No. 20, consequently, the magnetic flux densities decreased as a whole in both cases. Similarly, since the intermediate annealing temperature was too low in Test No. 21, and, conversely, the intermediate annealing temperature was too high in Test No. 22, consequently, the magnetic flux densities decreased as a whole in both cases.

[0156] In Test No. 23, the iron loss and the magnetic flux density were excellent, but the second cold rolling ratio was low, and thus the anisotropy was not relaxed. On the other hand, in Test No. 24, since the second cold rolling ratio was too high, the deviation from the {100} <011> crystal orientation became large, and consequently, the magnetic flux density decreased as a whole.

[0157] In Test No. 25, since the final annealing temperature was too low, consequently, grains did not grow, and the anisotropy was too strong. On the other hand, in Test No. 26, since the final annealing temperature was too high, α-γ transformation occurred and the structure was randomized, and thus, consequently, the magnetic flux density decreased as a whole. Furthermore, in Test No. 27, since annealing was not performed on the hot rolled sheet, Mn segregated at grain boundaries and cracks were generated after cold rolling, which stopped the experiment.

INDUSTRIAL APPLICABILITY

[0158] As described above, according to the present invention, an electrical steel sheet having excellent magnetic characteristics not only in a 45° direction from the rolling direction but also in the peripheral directions can be obtained.