Directional electric steel plate having excellent magnetic properties and manufacturing method thereof

1. A directional electric steel plate comprising:

a steel plate consisting of Si: 2.0 to 6.5%, acid soluble Al: 0.04 to 5%, Mn: 0.20% or less (0% exclusive), N: 0.010% or less (0% exclusive), S: 0.010% or less (0% exclusive), P: 0.005 to 0.05%, C: 0.04 to 0.12%, both Sb and Sn: 0.01 to 0.15% and a balance of Fe and other unavoidable impurities, by wt %;

a hot-dip plated layer formed on a surface of the steel plate and consisting of an aluminum-silicon alloy; and

an oxide layer formed on the hot-dip plated layer and consisting of an oxide of aluminum-silicon alloy,

wherein the aluminum-silicon alloy includes more than 0 wt % to 60 wt % of silicon, and

wherein the hot-dip plated layer formed on a surface of the steel plate consisting of the aluminum-silicon alloy and the aluminum-silicon alloy includes 10 to 30 wt % of silicon.

2. The directional electric steel plate of claim 1 , wherein:

the hot-dip plated layer has an unplating rate of 15 area % or less.

3. A method of manufacturing a directional electric steel plate, comprising:

preparing a steel slab consisting of Si: 2.0 to 6.5%, acid soluble Al: 0.04% or less (0% exclusive), Mn: 0.20% or less (0% exclusive), N: 0.010% or less (0% exclusive), S: 0.010% or less (0% exclusive), P: 0.005 to 0.05%, C: 0.04 to 0.12%, both Sb and Sn: 0.01 to 0.15% and a balance of Fe and other unavoidable impurities, by wt %; reheating the steel slab to a temperature of 1250° C. or less;

subjecting the reheated slab to hot rolling, hot band annealing and cold rolling to manufacture a steel plate; subjecting the cold rolled steel plate to decarburizing annealing and nitriding treatment simultaneously or sequentially; and

finally annealing the steel plate subjected to decarburizing annealing and nitriding treatment,

wherein during or after the decarburizing annealing and nitriding treatment, hot-dip plating aluminum-silicon binary molten metal, and oxidizing a surface of a hot-dip plated layer are further comprised,

wherein the aluminum-silicon alloy hot-dip plated on the steel plate includes more than 0 wt % to 60 wt % of silicon,

wherein the aluminum-silicon alloy hot-dip plated on the steel plate includes 10 to 30 wt % of silicon.

4. The method of claim 3 , wherein:

the hot-dip plating of aluminum or aluminum-silicon binary molten metal is carried out at a temperature of 600 to 900° C.

5. The method of claim 3 , wherein:

the hot-dip plating of aluminum or aluminum-silicon binary molten metal is carried out so that the hot-dip plated layer has an unplating rate of 15% or less.

6. The method of claim 3 , further comprising:

reducing some or entire of an outer oxide layer formed on a surface of the decarburizing and nitriding annealed steel plate, before the hot-dip plating of aluminum or aluminum-silicon binary molten metal.

7. The method of claim 3 , wherein:

the hot band annealing is carried out by heating to 900 to 1200° C., performing crack heat treatment, and cooling.

8. The method of claim 3 , wherein:

the cold rolling is carried out at a cold rolling rate of 87% or more by a single strong cold rolling.

9. The method of claim 3 , wherein:

the decarburizing annealing and nitriding treatment is carried out at a temperature of 800 to 950° C.

10. The method of claim 3 , further comprising:

coating a magnesium oxide-based or aluminum oxide-based annealing separator before the final annealing.