Apparatus and method for trimming a side of steel plate

1. A side trimming apparatus comprising:

a cutting unit which is installed on at least one side of a steel plate being transferred and trims a side of the steel plate through mechanical cutting; and

a laser processing unit which is installed in front of the cutting unit and emits a laser beam to a portion of the steel plate to be cut to form a groove at the portion to be cut or preheat the portion to be cut.

2. The side trimming apparatus of claim 1 , wherein the cutting unit comprises:

a stand;

an upper rotatable knife installed at the stand and disposed above the steel plate; and

a lower rotatable knife installed at the stand and disposed below the steel plate to apply a shearing force to the side of the steel plate together with the upper knife.

3. The side trimming apparatus of claim 2 , wherein the laser processing unit comprises:

a laser oscillator which generates a laser beam; and

an optical condensing head which is installed at the stand and focuses the laser beam of the laser oscillator on the steel plate.

4. The side trimming apparatus of claim 3 , wherein the optical condensing head is installed at the stand to be rotatably driven to adjust an emission position of the laser beam.

5. The side trimming apparatus of claim 3 , wherein a plurality of such optical condensing heads are provided above and below the steel plate respectively to emit laser beams to upper and lower surfaces of the steel plate.

6. The side trimming apparatus of claim 1 , further comprising a gas jet unit which jets an auxiliary gas to a portion of the groove formed by the laser processing unit.

7. The side trimming apparatus of claim 6 , wherein the gas jet unit has a tilt angle from 45° to 80° with respect to a direction perpendicular to the steel plate.

8. The side trimming apparatus of claim 1 , further comprising a controller which is connected to the laser processing unit and controls the laser processing unit to adjust a spot shape or size of the laser beam.

9. The side trimming apparatus of claim 1 , further comprising a controller which is connected to the laser processing unit and controls a laser output of the laser processing unit.

10. The side trimming apparatus of claim 9 , wherein the controller controls an output of the laser processing unit to maintain a temperature of a cut portion cut by the cutting unit to be within a range from 400° C. to 600° C.

11. The side trimming apparatus of claim 9 , further comprising an input portion which is connected to the controller and receives at least one of transfer speed information and steel grade information of the steel plate input from a main controller of a cold rolling line,

wherein the controller controls the output of the laser processing unit based on the input information of the input portion.