Strip edge shape control apparatus and method in strip casting process

Abstract

Disclosed herein are an apparatus and method for controlling the edge shape of a strip in a twin-roll strip casting process, which improve the quality of the strip by using cameras to photograph the edge portions of the strip being cast by strip casting, analyzing the photographs, and then controlling edge dams according to the edge shape of the strip. The apparatus comprises: an edge dam driving unit which is attached to edge dams attached to both sides of casting rolls so as to control the pressing force of the edge dams against the casting rolls and the upward shift of the edge dams according to the wear and upward shift rate of the edge dams; cameras which are disposed at the strip outlet side of the casting rolls so as to photograph the edge portions of the strip; and a control unit which analyzes the edge shape of the strip from images photographed by the cameras and outputs a signal controlling the wear and upward shift of the edge dams.

1 . An apparatus for controlling the edge shape of a strip in a twin-roll casting process, the apparatus comprising:
 an edge dam driving unit which is attached to edge dams attached to both sides of casting rolls so as to control the pressing force of the edge dams against the casting rolls and the upward shift of the edge dams according to the wear and upward shift rate of the edge dams;   cameras which are disposed at the strip outlet side of the casting rolls so as to photograph the edge portions of the strip; and   a control unit which analyzes the edge shape of the strip from images photographed by the cameras and outputs a signal controlling the wear and upward shift of the edge dams.   
     
     
         2 . The apparatus of  claim 1 , wherein the edge dam driving unit comprises:
 an upward cylinder which is disposed at the upper area of the center of the side opposite the side of the edge dams that comes in contact with the casting rolls, so as to move the edge dams upward; and   wear cylinders which are disposed at the left and right sides of the upper portion of the edge dams and at the lower portion of the center of the edge dams so as to press the edge dams against the casting rolls.   
     
     
         3 . The apparatus of  claim 2 , wherein the control unit comprises:
 a main control unit which analyzes the strip edge images photographed by the cameras so as to calculate the wear and upward shift rate of the edge dams;   an upward-shift control unit which outputs a signal driving the upward cylinder depending on the upward shift rate and target shift rate of the main control unit;   an upward-cylinder servo-valve which drives the upward cylinder according to the driving signal of the upward-shift control unit;   a wear control unit which outputs a signal driving the wear cylinders according to the wear rate calculated in the main control unit; and   a wear cylinder servo-valve which drives the wear cylinders according to the driving signal of the wear control unit.   
     
     
         4 . A method for controlling the edge shape of a strip in a twin-roll casting process, the method comprising:
 a photographing step of photographing the images of edge portions of the strip using cameras disposed at the strip outlet sides of casting rolls;   a control signal-producing step of analyzing the strip edge images photographed in the photographing step and outputting a control signal for a wear and upward shift rate; and   an edge dam control step of controlling the wear and upward shift of edge dams according to the control signal output in the control signal-producing step.   
     
     
         5 . The method of  claim 4 , wherein the control signal-producing step comprises:
 an edge analysis step of calculating the burr thickness of the edge dams and the length of an edge fin;   a step of outputting a signal for maintaining the edge dams at a default wear and upward shift rate set in the normal state of the edge dams, if the edge analysis step shows a burr thickness of less than 1 mm and no existence of the edge fin;   a step of outputting a signal for additionally applying a wear and upward shift rate of 1 μm per m of the strip to the default wear and upward shift rate, if the edge analysis step shows a burr thickness of more than 1 mm but less than 5 mm and an edge fin length of less than 1 cm; and   a step of outputting a signal for additionally applying a wear and upward shift rate of 1.5 μm per m of the strip to the default wear and upward shift rate, if the edge analysis step shows a burr thickness of more than 5 mm and an edge fin length of more than 1 cm.   
     
     
         6 . The method of  claim 4 , wherein the edge dam control step comprises the steps of:
 re-analyzing the edge portions of the strip after performing the control of the edge dams according to the signal output in the control signal-producing step; and   controlling the edge dams so as to return to the default value of the edge dam wear and upward shift rate, if the edge portions are normal.   
     
     
         7 . The method of  claim 5  or  6 , wherein the default value of the wear and upward shift rate is set within the range of 0.5 to 5 μm per m of the strip.