A THERMOMICROSTRUCTURAL MODEL FOR SIMULATION DISTURBANCES IN A HOT STRIP MILL AND ITS EFFECT IN STEEL PROPERTIES, ROLL FORCE AND EXIT STRIP THICKNESS

Abstract

USING HOT STRIP MILL INDUSTRIAL DATA AND A THERMOMICROSTRUCTURAL MODEL WAS DEVELOPMENT TO TAKING INTO ACCOUNT THE EFFECT OF THE STRIP TENSION AND THE WORK ROLL GAP AND THE STATIC, DYNAMIC AND METADYNAMIC RECRYSTALLIZATION TO CALCULATE THE AUSTENITE GRAIN SIZE, MEAN FLOW STRESS THAT OCCURS IN THE STEEL AND ALSO THE ROLL FORCE, EXIT STRIP THICKNESS AND STEEL ENTRY TEMPERATURES IN EACH STAND. OPERATIONAL DISTURBANCES IN THE THERMOMICROSTRUCTURAL MODEL WERE INTRODUCED IN THE STRIP TENSION AND IN THE WORK ROLL GAP. THE SENSITIVITY CURVES WERE PLOTTED AND SHOWED THE CHANGES OF THESE DISTURBANCES AFFECT ON THE STEEL PROPERTIES. THE MODEL SHOWED THAT BY INCREASING THE GAP OF THE PREVIOUS STAND INCREASES THE MEAN FLOW STRESS, AND CONSEQUENTLY THE ROLL FORCE. THESE DISTURBANCES INCREASE THE EXIT STRIP THICKNESS, THE STRIP TEMPERATURE IN ALL THE STANDS AND CAN CAUSE DYNAMIC AND METADYNAMIC RECRYSTALLIZATION IN THE FOLLOWING PASSES. IN ADDITION, BY INCREASING THE GAP WITHIN THE STAND ITSELF REDUCES THE MEAN FLOW STRESS AND THE STRIP TEMPERATURE, AND THEREBY RESULTS IN AN INCREASE IN THE EXIT STRIP THICKNESS. A GROUP OF QUALITATIVE RULES WERE ELABORATED TO SHOW WHICH ACTIONS SHOULD BE TAKEN IF THE DISTURBANCES OCCUR, AIMING TO RECOVER THE STRIP THICKNESS AND IMPROVE STEEL PROPERTIES.