Grain-oriented electrical steel sheet and manufacturing method therefor
A grain-oriented electrical steel sheet of an embodiment of the present invention comprises Si: 1.0% to 7.0% and Y: 0.005% to 0.5% by wt %, and the remainder comprising Fe and other inevitable impurities, and 10 pieces or less of inclusions comprising Y and having a diameter of 30 nm to 5 μm per area of 1 mm 2 .
1. A grain-oriented electrical steel sheet comprising:
Si: 1.0 to 7.0% and Y: 0.005 to 0.5% by wt %, and the remainder comprising Fe and other inevitable impurities, and
3 to 9 pieces of inclusions comprising Y and having a diameter of 30 nm to 5 μm per area of 1 mm 2 .
2. The grain-oriented electrical steel sheet of claim 1 , further comprising
Mn: 0.01% to 0.5%, C: 0.005% or less (excluding 0%), Al: 0.005% or less (excluding 0%), N: 0.006% or less (excluding 0%) and S: 0.006% or less (excluding 0%) by wt %.
3. The grain-oriented electrical steel sheet of claim 1 , further comprising
0.01 to 0.2 wt % of at least one of P, Cu, Cr, Sb, Sn and Mo, respectively singly or in a total amount.
4. The grain-oriented electrical steel sheet of claim 1 , wherein,
the inclusions comprise at least one of a carbide of Y, a nitride of Y, an oxide of Y, and an Fe—Y compound.
5. A method for manufacturing the grain-oriented electrical steel sheet of claim 1 , the method comprising:
heating a slab comprising Si: 1.0 to 7.0%, Y: 0.005 to 0.5% by wt %, and the remainder comprising Fe and other inevitable impurities;
hot-rolling the slab to produce a hot-rolled sheet;
cold-rolling the hot-rolled sheet to produce a cold-rolled sheet;
primary recrystallization annealing the cold-rolled sheet; and
secondary recrystallization annealing the cold-rolled sheet which is the primary recrystallization annealed;
wherein the step of the primary recrystallization annealing comprises a heating step and a soaking step,
the heating step is performed in an atmosphere having an oxygen partial pressure (P H2O /P H2 ) of 0.20 to 0.40, and
the soaking step of soaking is performed in an atmosphere having an oxygen partial pressure (P H2O /P H2 ) of 0.50 to 0.70.
6. The method of claim 5 , wherein,
the slab further comprises Mn: 0.01% to 0.5%, C: 0.02 to 0.1%, Al: 0.01% or less (excluding 0%), N: 0.006% or less (excluding 0%) and S: 0.006% or less (excluding 0%) by wt %.
7. The method of claim 5 , wherein,
the slab further comprises 0.01 to 0.2 wt % of at least one of P, Cu, Cr, Sb, Sn and Mo, respectively singly or in a total amount.
8. The method of claim 5 , wherein,
in the step of the heating the slab, heating is performed at 1000 to 1280° C.
9. The method of claim 5 , wherein,
the heating step of the primary recrystallization annealing is heating at a rate of 10° C./s or more.
10. The method of claim 5 , wherein,
the soaking step is performed at a temperature of 800 to 900° C.
11. The method of claim 5 , wherein,
the step of the primary recrystallization annealing is performed in a mixed gas atmosphere of hydrogen and nitrogen.
12. The method of claim 5 , wherein,
the step of the secondary recrystallization annealing comprises a temperature-raising step and a soaking step, and a temperature of the soaking step is 900 to 1250° C.
13. The method of claim 12 , wherein,
the temperature-raising step of the secondary recrystallization annealing is performed in a mixed gas atmosphere of hydrogen and nitrogen, and the soaking step of the secondary recrystallization annealing is performed in hydrogen atmosphere.
14. A grain-oriented electrical steel sheet consisting of:
Si: 1.0 to 7.0% and Y: 0.005 to 0.5% by wt %, and the remainder consisting of Fe and other inevitable impurities, and
3 to 9 pieces of inclusions comprising Y and having a diameter of 30 nm to 5 μm per area of 1 mm 2 ,
wherein the grain-oriented electrical steel sheet optionally consists of: Mn: 0.01% to 0.5%, C: 0.005% or less (excluding 0%), Al: 0.005% or less (excluding 0%), N: 0.006% or less (excluding 0%) or S: 0.006% or less (excluding 0%) by wt %, and optionally further consists of: 0.01 to 0.2 wt % of at least one of P, Cu, Cr, Sb, Sn and Mo, respectively singly or in a total amount.
15. The grain-oriented electrical steel sheet of claim 14 consisting of:
Si: 1.0 to 7.0% and Y: 0.005 to 0.5% by wt %, and the remainder consisting of Fe and other inevitable impurities.
16. The grain-oriented electrical steel sheet of claim 14 , wherein the grain-oriented electrical steel sheet does not include Ba as a grain growth inhibitor.