Patent ID: 6918966

Claim:
A low iron loss and low noise grain-oriented electrical steel sheet, having: ε OC , an absolute value deviated by forming a tension film from a standard value which is defined as ε O in the state that a tension film substantially does not exist and laser is not irradiated, and ε OL , an absolute value deviated by irradiating laser after the film formation from the value in the state of tension film only, satisfying the following expressions; ε OC <3.0×10 −6 ε OL <1.0×10 −6 , wherein ε O is defined as a zero-peak value of magnetostriction vibration when a grain-oriented electrical steel sheet is magnetized up to a saturated magnetic flux density at the frequency of 50 Hz in the rolling direction; and ε 17C , an absolute value deviated by forming a tension film from a standard value which is defined as ε 17 in the state that a tension film substantially does not exist and laser is not irradiated, and ε 17L , an absolute value deviated by irradiating laser after film formation from the value in the state of tension film only, satisfying the following expressions; ε 17C <1.5×10 −6 ε 17L <0.3×10 −6 , wherein ε 17 is defined as the value obtained by subtracting a zero-peak value of magnetostriction vibration at the magnetization magnetic flux density of 1.7 T from a zero-peak value of magnetostriction vibration at a saturated magnetic flux density at the frequency of 50 Hz in the rolling direction; and further λ 17 , a zero-peak value of magnetostriction vibration at the magnetization magnetic flux density of 1.7 T, satisfying the following expression; −0.5×10 −6 ≦λ 17 ≦0.5×10 −6 ; when magnetizing a grain-oriented electrical steel sheet at the frequency of 50 Hz in the rolling direction and measuring a zero-peak value, O-p value, magnetostriction vibration in the rolling direction, wherein O-p value is the value of expansion or contraction at a certain magnetization magnetic flux density determined on the basis of the value in the state of demagnetization, which is positive in case of expansion and negative in case of contraction.