Non-oriented electrical steel sheet and manufacturing method therefor
A non-oriented electrical steel sheet according to one embodiment of the present invention comprises, by weight, 1.0% to 4.0% of Si, 0.001% to 0.01% of Al, 0.002% to 0.009% of S, 0.01% to 0.3% of Mn, 0.001% to 0.004% of N, 0.004% or less (0% exclusive) of C, 0.003% or less (0% exclusive) of Ti, 0.005% to 0.07% of Cu, 0.05% to 0.2% of either or both of Sn and P, and a balance amount of Fe and impurities.
1. A non-oriented electrical steel sheet, comprising
by weight, 1.0% to 4.0% of Si, 0.001% to 0.01% of Al, 0.002% to 0.009% of S, 0.01% to 0.3% of Mn, 0.001% to 0.004% of N, 0.004% or less and 0% exclusive of C, 0.003% or less and 0% exclusive of Ti, 0.005% to 0.07% of Cu, 0.05% to 0.2% of either or both of Sn and P, and a balance amount of Fe and impurities, and satisfying [Equation 1], wherein a number of an inclusion of N compositely with S is larger than a number of an inclusion of N alone in the steel sheet,
log
(
[
Mn
]
+
[
Cu
]
)
×
[
S
]
(
[
Al
]
+
[
Ti
]
)
×
[
N
]
≥
0.85
[
Equation
1
]
in [Equation 1], [Mn], [Cu], [S], [Al], [Ti], and [N] denote each content wt % of Mn, Cu, S, Al, Ti, and N,
wherein a volume fraction of a <100>∥ND crystal grain is greater than or equal to 15%, a volume fraction of a <100>∥ND crystal grain is greater than a volume fraction of a <111>∥ND crystal grain, and an average crystal grain size is smaller than the sheet thickness, wherein <100>∥ND means that a <100> axis of the crystal grain is within 15° from an axis (ND) perpendicular to an axis of the surface of the steel sheet and <111>∥ND means that a <111> axis of the crystal grain is within 15° from an axis (ND) perpendicular to an axis of the surface of the steel sheet.
2. The non-oriented electrical steel sheet of claim 1 , wherein at least one of Ni and Cr is further included in an amount of 0.01 wt % to 0.1 wt % alone or as a mixture.
3. The non-oriented electrical steel sheet of claim 1 , wherein 0.005 wt % to 0.06 wt % of Sb is further included.
4. The non-oriented electrical steel sheet of claim 1 , wherein 0.001 wt % to 0.015 wt % of Mo is further included.
5. The non-oriented electrical steel sheet of claim 1 , wherein at least one of Bi, Pb, Mg, As, Nb and V is further included in each amount of 0.0005 wt % to 0.005 wt %.
6. The non-oriented electrical steel sheet of claim 1 , wherein Br value measured in a direction in which Br magnetic flux density is the highest on the sheet surface is greater than or equal to 1.79 T, a Br value measured after 90° rotating relative to a perpendicular axis of the sheet surface in the direction is greater than or equal to 1.72 T, and a Br value in a circumferential direction relative to a perpendicular axis of the sheet surface is greater than or equal to 1.71 T
the Br is calculated by [Equation 2]:
Br
=
7.87
(
7.87
-
0.065
×
[
Si
]
-
0.1105
×
[
Al
]
)
×
B
50
wherein, in [Equation 2], [Si] and [Al] denote each wt % content of Si and Al, and B50 denotes a strength (T) of a magnetic field induced when being placed at 5,000 A/m.
7. The non-oriented electrical steel sheet of claim 1 , wherein a hardness on the surface of the sheet measured using a Vickers hardness method is 0.1 Hv to 10 Hv larger than a hardness of the cross-section of the sheet and the hardness of the surface ranges from 130 Hv to 210 Hv.
8. The non-oriented electrical steel sheet of claim 1 , wherein a W15/100 (W/kg) value measured using an Epstein method divided by the square of the thickness of the sheet is greater than or equal to 20 mm and less than or equal to 100 mm, wherein the W15/100 (W/kg) value refers to a loss generated when being excited at 1.5 T under a 100 Hz AC sinusoidal frequency condition.
9. The non-oriented electrical steel sheet of claim 6 , wherein a Br value after annealing at 750° C. for 2 hours is greater than or equal to 1.75 (T) and relative permeability at B 0.5 is greater than or equal to 8000μ, wherein, B 0.5 is a strength of a magnetic field when being placed at 50 A/m and the relative permeability is B 0.5 /(50×4×π×10 −7 ).