NON-ORIENTED ELECTRICAL STEEL SHEET

Abstract

This non-oriented electrical steel sheet includes a base metal having a predetermined chemical composition satisfying the expression [Si+0.5×Mn≥4.3], and an average grain size of the base metal is more than 40 μm and 120 μm or less.

Claims

1. A non-oriented electrical steel sheet comprising: a base metal containing, as a chemical composition, by mass %, C: 0.0050% or less, Si: 3.5% to 5.0%, Mn: more than 0.2% and less than 2.0%, P: 0.030% or less, S: 0.0050% or less, sol. Al: 0.0030% or less, N: 0.0030% or less, Ti: less than 0.0050%, Nb: less than 0.0050%, Zr: less than 0.0050%, V: less than 0.0050%, Cu: less than 0.200%, Ni: less than 0.500%, Sn: 0 to 0.100%, Sb: 0 to 0.100%, and a remainder: Fe and impurities, wherein Expression (i) is satisfied, and an average grain size of the base metal is more than 40 μm and 120 μm or less,
Si+0.5×Mn≥4.3  (i) where element symbols in the expression represent amounts of respective elements in mass %.

2. The non-oriented electrical steel sheet according to claim 1, wherein an elastic modulus of the non-oriented electrical steel sheet in a direction parallel to a rolling direction is 175,000 MPa or more.

3. The non-oriented electrical steel sheet according to claim 1, wherein a tensile strength of the non-oriented electrical steel sheet is 600 MPa or more.

4. The non-oriented electrical steel sheet according to claim 1, wherein the chemical composition includes, by mass %, one or two of Sn: 0.005% to 0.100%, and Sb: 0.005% to 0.100%.

5. The non-oriented electrical steel sheet according to claim 1, further comprising: an insulation coating on a surface of the base metal.

6. The non-oriented electrical steel sheet according to claim 2, wherein a tensile strength of the non-oriented electrical steel sheet is 600 MPa or more.

7. The non-oriented electrical steel sheet according to claim 2, wherein the chemical composition includes, by mass %, one or two of Sn: 0.005% to 0.100%, and Sb: 0.005% to 0.100%.

8. The non-oriented electrical steel sheet according to claim 3, wherein the chemical composition includes, by mass %, one or two of Sn: 0.005% to 0.100%, and Sb: 0.005% to 0.100%.

9. The non-oriented electrical steel sheet according to claim 6, wherein the chemical composition includes, by mass %, one or two of Sn: 0.005% to 0.100%, and Sb: 0.005% to 0.100%.

10. The non-oriented electrical steel sheet according to claim 2, further comprising: an insulation coating on a surface of the base metal.

11. The non-oriented electrical steel sheet according to claim 3, further comprising: an insulation coating on a surface of the base metal.

12. The non-oriented electrical steel sheet according to claim 4, further comprising: an insulation coating on a surface of the base metal.

13. The non-oriented electrical steel sheet according to claim 6, further comprising: an insulation coating on a surface of the base metal.

14. The non-oriented electrical steel sheet according to claim 7, further comprising: an insulation coating on a surface of the base metal.

15. The non-oriented electrical steel sheet according to claim 8, further comprising: an insulation coating on a surface of the base metal.

16. The non-oriented electrical steel sheet according to claim 9, further comprising: an insulation coating on a surface of the base metal.

Description

EXAMPLES

[0128] Hereinafter, the present invention will be described in more detail with reference to examples, but the conditions in the examples are merely examples adopted for confirming the feasibility and effect of the present invention, and the present invention is limited to the examples of the conditions. In the present invention, various conditions can be adopted as long as the object of the present invention is achieved without departing the gist of the present invention.

Example 1

[0129] A slab having the composition shown in Table 1 was heated to 1150° C., hot-rolled to a finishing sheet thickness of 2.0 mm at a finishing temperature of 850° C., and coiled at 650° C. to obtain a hot-rolled steel sheet. The obtained hot-rolled steel sheet was subjected to hot-rolled sheet annealing at 970° C. for 50 seconds, and pickled to remove scale on the surface. The pickled steel sheet thus obtained was cold-rolled to obtain a cold-rolled steel sheet having a sheet thickness of 0.25 mm.

[0130] Furthermore, annealing was performed to achieve the average grain size as shown in Table 2 below while changing final annealing conditions in a mixed atmosphere of H.sub.2: 20% and N.sub.2: 80% with a dew point 0° C. at an annealing temperature of 900° C. to 1050° C. for a soaking time in a range of 1 to 300 seconds. Specifically, in a case where the average grain size was controlled to be large, the final annealing temperature was further raised and/or the soaking time was further lengthened. In a case where the average grain size was controlled to be small, the reverse was applied. Thereafter, an insulation coating was applied to manufacture a non-oriented electrical steel sheet, which was used as a test material.

[0131] The above-mentioned insulation coating was formed by applying an insulation coating containing aluminum phosphate and an acrylic-styrene copolymer resin emulsion having a particle size of 0.2 μm so as to have a predetermined adhesion amount and baking the resultant in the air at 350° C.

TABLE-US-00001 TABLE 1 Formula Kind Chemical composition (i)* left of (mass %, remainder: Fe and impurities) side steel C Si Mn P S sol .Math. Al N Ti Nb Zr V Cu Ni Sn Sb value A 0.0025 3.4 1.8 0.007 0.0028 0.0008 0.0012 0.0012 0.0008 0.0007 0.0002 0.062 0.033 (0.001) (0.001) 4.3 B 0.0025 3.9 1.6 0.008 0.0029 0.0007 0.0013 0.0013 0.0008 0.0007 0.0018 0.053 0.035 (0.001) (0.001) 4.7 C 0.0020 4.2 1.6 0.007 0.0028 0.0008 0.0013 0.0012 0.0009 0.0006 0.0005 0.061 0.050 (0.001) (0.001) 5.0 D 0.0025 4.5 1.6 0.008 0.0026 0.0008 0.0015 0.0016 0.0007 0.0004 0.0001 0.058 0.049 (0.001) (0.001) 5.3 E 0.0025 5.1 1.6 0.008 0.0027 0.0008 0.0015 0.0016 0.0008 0.0004 0.0006 0.052 0.050 (0.001) (0.001) 5.9 F 0.0024 3.8 0.4 0.007 0.0020 0.0009 0.0014 0.0015 0.0007 0.0011 0.0009 0.007 0.005 0.030 (0.001) 4.0 G 0.0018 4.0 1.0 0.009 0.0014 0.0009 0.0015 0.0025 0.0014 0.0006 0.0009 0.009 0.006 0.028 (0.001) 4.5 H 0.0022 4.0 1.6 0.008 0.0015 0.0010 0.0017 0.0012 0.0016 0.0006 0.0001 0.005 0.005 0.030 (0.001) 4.8 I 0.0025 4.0 2.6 0.009 0.0014 0.0010 0.0018 0.0012 0.0016 0.0005 0.0001 0.006 0.006 0.030 (0.001) 5.3 J 0.0021 4.0 1.6 0.045 0.0026 0.0009 0.0010 0.0011 0.0014 0.0004 0.0008 0.005 0.006 0.030 (0.001) 4.8 K 0.0024 4.0 1.6 0.008 0.0065 0.0009 0.0014 0.0010 0.0015 0.0005 0.0008 0.006 0.006 0.029 (0.001) 4.8 L 0.0027 4.2 0.8 0.009 0.0027 0.0007 0.0015 0.0010 0.0004 0.0001 0.0006 0.012 0.080 (0.001) 0.030 4.6 M 0.0026 4.2 0.8 0.008 0.0025 0.0008 0.0012 0.0011 0.0006 0.0005 0.0004 0.013 0.085 0.040 0.013 4.6 N 0.0023 4.2 0.8 0.007 0.0025 0.0009 0.0014 0.0011 0.0006 0.0005 0.0003 0.013 0.092 0.039 0.001 4.6 0 0.0029 4.2 0.8 0.007 0.0009 0.0045 0.0013 0.0012 0.0005 0.0005 0.0003 0.012 0.086 0.040 0.001 4.6 P 0.0025 4.1 1.6 0.008 0.0025 0.0007 0.0013 0.0013 0.0009 0.0007 0.0005 0.040 0.088 0.021 0.001 4.9 Q 0.0018 4.1 1.0 0.009 0.0014 0.0009 0.0016 0.0027 0.0015 0.0008 0.0009 0.009 0.007 0.026 (0.001) 4.6 R 0.0022 4.1 0.5 0.008 0.0022 0.0008 0.0015 0.0024 0.0010 0.0009 0.0008 0.060 0.035 0.025 (0.001) 4.4 S 0.0023 4.1 0.6 0.009 0.0023 0.0009 0.0016 0.0023 0.0011 0.0010 0.0008 0.060 0.034 0.023 (0.001) 4.4 *Si + 0.5 × Mn ≥ 4.3 . . . (i)
Parentheses indicate that they were not added intentionally and that they were below the detection limit

TABLE-US-00002 TABLE 2 Average Test results Kind grain Tensile Test of size strength W.sub.10/400 B.sub.50 No. steel (μm) (MPa) (W/kg) (T) Note 1 A 53 559 12.3 1.65 Comparative Example 2 B 17 710 18.0 1.63 Present Invention 3 B 60 610 11.6 1.63 Example 4 B 124 575 11.8 1.62 Comparative Example 5 C 53 656 11.2 1.62 Present Invention 6 D 56 686 11.1 1.60 Example 7 E Fractured during cold rolling Comparative 8 F 62 578 13.2 1.67 Example 9 G 63 612 11.8 1.65 Present Invention 10 H 61 621 11.3 1.64 Example 11 I 62 635 12.6 1.59 Comparative 12 J Fiactured during cold rolling Example 13 K 62 620 13.6 1.63 14 L 49 646 11.8 1.65 Present Invention 15 M 51 644 11.5 1.65 Example 16 N 18 729 17.5 1.66 Comparative Example 17 N 52 642 11.4 1.65 Present Invention 18 N 75 622 11.0 1.65 Example 19 N 127 596 11.5 1.64 Comparative 20 O 51 644 13.3 1.63 Example 21 P 19 724 16.5 1.64 22 P 45 651 11.8 1.63 Present Invention 23 P 71 625 11.0 1.63 Example 24 P 97 613 10.8 1.63 25 P 137 594 11.9 1.61 Comparative Example 26 Q 63 624 11.2 1.65 Present Invention 27 R 61 616 11.6 1.66 Example 28 S 61 620 11.5 1.66
Underline indicates outside of the range of the invention.

[0132] For each of the obtained test materials, the average grain size of the base metal was measured according to JIS G 0551 (2013) “Steel-Particle Size Microscopic Test Method”. In addition, an Epstein test piece was taken from the rolling direction and width direction of each of the test materials, and the magnetic characteristics (iron loss W.sub.10/400 and magnetic flux density B.sub.50) were evaluated by the Epstein test according to JIS C 2550-1 (2011). A case where the iron loss W.sub.10/400 was 13.0 W/kg or less and the magnetic flux density B.sub.50 was 1.60 T or more was regarded as having excellent magnetic characteristics and determined to be acceptable. A case where this condition was not satisfied was regarded as having inferior magnetic characteristics and determined as unacceptable. The acceptance condition was set because the sheet thickness of each of the test materials was more than 0.20 mm and 0.25 mm or less.

[0133] Furthermore, from each of the test materials, a JIS No. 5 tensile test piece was taken according to JIS Z 2241 (2011) so that the longitudinal direction thereof coincided with the rolling direction of the steel sheet. Then, a tensile test was conducted using the above test piece according to JIS Z 2241 (2011), and the tensile strength was measured. A test piece in which the tensile strength was 600 MPa or more was regarded as having high strength and determined to be acceptable. A test piece in which the tensile strength was less than 600 MPa was regarded as having inferior strength and determined to be unacceptable.

[0134] The above results are also shown in Table 2.

[0135] It could be seen that in Test Nos. 3, 5, 6, 9, 10, 14, 15, 17, 18, 22 to 24, and 26 to 28 in which the chemical composition of the steel sheet and the average grain size after the final annealing satisfied the requirements of the present invention, the iron loss was low, the magnetic flux density was high, and the tensile strength was as high as 600 MPa or more.

[0136] On the other hand, in Test Nos. 1, 2, 4, 7, 8, 11 to 13, 16, 19 to 21, and 25 which are comparative examples, at least one of the magnetic characteristics and the tensile strength was inferior, or the toughness was significantly deteriorated, which made manufacturing difficult.

[0137] Specifically, in Test No. 1, the Si content was lower than the specified range, and the result was that the tensile strength was inferior. In addition, when Test Nos. 2 to 4 in which the chemical composition satisfied the requirements were compared to each other, the result was that in Test No. 2, the average grain size was smaller than the specified range, and thus the iron loss was inferior, while in Test No. 4, the average grain size was larger than the specified range, and the tensile strength was inferior.

[0138] In addition, in Test No. 7, the Si content exceeded the specified range, and in Test No. 12, the P content exceeded the specified range. Therefore, the toughness was deteriorated, fracture had occurred during the cold rolling, and thus the average grain size, tensile strength, and magnetic characteristics could not be measured. In Test No. 8, Expression (i) was not satisfied, and the result was that iron loss and the tensile strength were inferior. Furthermore, in Test No. 11, the Mn content exceeded the specified range, and the result was that the magnetic flux density was inferior.

[0139] In Test No. 13, the S content exceeded the specified range, and the result was that the iron loss was inferior. When Test Nos. 16 to 19 in which the chemical composition satisfied the requirements were compared to each other, the result was that in Test No. 16, the average grain size was smaller than the specified range, and thus the iron loss was inferior, while in Test No. 19, the average grain size was larger than the specified range, and thus the tensile strength was inferior.

[0140] In addition, in Test No. 20, the sol. Al content exceeded the specified range, and the result was that the magnetic characteristics were inferior to those of Test No. 15 having substantially the same chemical composition and average grain size except for sol. Al.

[0141] When Test Nos. 21 to 25 in which the chemical composition satisfied the requirements were compared to each other, the result was that in Test No. 21, the average grain size was smaller than the specified range, and thus the iron loss was inferior, while in Test No. 25, the average grain size was larger than the specified range, and thus the tensile strength was inferior.

Example 2

[0142] A slab having the composition shown in Table 3 was heated to 1150° C., hot-rolled to a finishing sheet thickness of 2.0 mm at a finishing temperature of 850° C., and coiled at 650° C. to obtain a hot-rolled steel sheet. The obtained hot-rolled steel sheet was subjected to hot-rolled sheet annealing by performing soaking at the hot-rolled sheet annealing temperature shown in Table 4 for 40 seconds, and pickled to remove scale on the surface. The pickled steel sheet thus obtained was cold-rolled to obtain a cold-rolled steel sheet having a sheet thickness of 0.25 mm.

[0143] Furthermore, final annealing was performed by performing soaking in a mixed atmosphere of H.sub.2: 15% and N.sub.2: 85% with a dew point −10° C. at the temperature shown in Table 4 for 15 seconds to obtain a final-annealed sheet having the average grain size as shown in Table 4. Thereafter, an insulation coating was applied to manufacture a non-oriented electrical steel sheet, which was used as a test material.

[0144] The above-mentioned insulation coating was formed by applying an insulation coating containing aluminum phosphate and an acrylic-styrene copolymer resin emulsion having a particle size of 0.2 μm so as to have a predetermined adhesion amount and baking the resultant in the air at 350° C.

[0145] For each of the obtained test materials, the average grain size of the base metal, magnetic characteristics (iron loss W.sub.10/400 and magnetic flux density B.sub.50), tensile strength, and elastic modulus in a direction parallel to the rolling direction were measured by the same method as in Example 1. The elastic modulus in a direction parallel to the rolling direction was measured by attaching strain gauges to both surfaces of the JIS No. 5 tensile test piece and conducting a tensile test in the same manner as for measuring the tensile strength. The elastic modulus was obtained from the slope of a stress-strain curve within an elastic range. Two stress-strain curves were obtained from the strain gauges attached to both surfaces of the test piece, and the average value of the elastic moduli respectively obtained from the stress-strain curves was calculated, thereby obtaining the elastic modulus. An elastic modulus in a direction parallel to the rolling method of 175,000 MPa or more was determined to be excellent in elastic modulus.

[0146] The other acceptance criteria were the same as in Example 1. The results are also shown in Table 4.

TABLE-US-00003 TABLE 3 Formula Kind Chemical composition (i)* left of (mass %, remainder: Fe and impurities) side steel C Si Mn P 5 sol .Math.Al N Ti Nb Zr V Cu Ni Sit Sb value A 0.0025 4.1 1.4 0.008 0.0026 0.0009 0.0018 0.0020 0.0009 0.0008 0.0005 0.055 0.036 0.022 (0.001) 4.8 B 0.0019 4.5 0.6 0.007 0.0023 0.0008 0.0016 0.0022 0.0007 0.0008 0.0006 0.060 0.040 0.020 (0.001) 4.8 C 0.0024 3.9 0.3 0.008 0.0015 0.0020 0.0021 0.0021 0.0008 0.0008 0.0006 0.057 0.037 0.100 (0.001) 4.1 D 0.0035 3.5 0.6 0.008 0.0018 0.0020 0.0020 0.0021 0.0008 0.0008 0.0006 0.057 0.037 (0.001) (0.001) 3.8 *Si + 0.5 × Mn ≥ 4.3 . . . (i)
Parentheses indicate that they were not added intentionally and that they were below the detection limit.

TABLE-US-00004 TABLE 4 Hot- Elastic rolled modulus Test sheet Final Average parallel results Kind annealing annealing grain to rolling Tensile Test of temperature temperature size direction strength W.sub.10/400 B.sub.50 No. steel (° C.) (° C.) (μm) (MPa) (MPa) (W/kg) (T) Note 1 A 850 980 70 180000 629 11.7 1.62 Present 2 A 940 980 72 178000 627 11.7 1.63 Invention 3 A 1000 980 75 173000 625 11.6 1.63 Example 4 B 900 850 24 185000 744 16.3 1.62 Comparative Example 5 B 900 950 58 180000 676 11.2 1.61 Present Invention Example 6 B 900 1050 150 171000 598 11.4 1.59 Comparative 7 C 940 900 55 176000 603 13.4 1.65 Example 8 C 950 980 75 175000 585 12.6 1.64 9 D 950 950 62 175000 551 13.5 1.64
Underline indicates outside of the range of the invention.

[0147] It could be seen that in Test Nos. 1, 2, and 5 in which the chemical composition of the steel sheet and the average grain size after the final annealing satisfied the regulations of the present invention and the temperature of the hot-rolled sheet annealing and the temperature of the final annealing were appropriately adjusted, the iron loss and the magnetic flux density were excellent, the iron loss was particularly low, the tensile strength was as high as 600 MPa or more, and the elastic modulus in a direction parallel to the rolling direction was 175,000 MPa or more.

[0148] On the other hand, in Test Nos. 4 and 6 to 9, which are comparative examples, any of the magnetic characteristics, tensile strength, and elastic modulus was inferior.

[0149] In Test Nos. 1 to 3 in which the chemical composition and average grain size satisfied the requirements, in Test No. 3, the hot-rolled sheet annealing temperature was high, and the result showed that the elastic modulus was inferior even in the examples of the present invention. When Test Nos. 4 to 6 in which the chemical composition satisfied the requirements were compared to each other, the result was that in Test No. 4, the average grain size was smaller than the specified range, and thus the iron loss was inferior, while in Test No. 6, the annealing temperature was too high, the average grain size was larger than the specified range, and the tensile strength, magnetic flux density, and elastic modulus were inferior. In Test Nos. 7 and 8 in which Expression (i) was not satisfied, in Test No. 7, the iron loss was interior, while in Test No. 8, the tensile strength was interior, and in Test No. 9, the iron loss and tensile strength were inferior.

INDUSTRIAL APPLICABILITY

[0150] As described above, according to the present invention, a non-oriented electrical steel sheet having high strength and excellent magnetic characteristics can be obtained.