Research And Development Of LF Furnace Electrode Lift Control System

Ladle furnace refining technology was originated from Japan in 1970's.Being an advanced refining process of steelmaking,Ladle furnace refining process is able to largely lower oxygen,sulphur,and other impurities contents in hot metal to improve the cleanliness of hot metal.Also,Ladle furnace refining provides a way to increase and maintain temperature of hot metal;this,in turn,gives more flexibility for continuous casting process.Because of these advantages,Ladle furnace has been employing in more and more steelmaking works.Triple electrodes heating system is the core part of Ladle furnace.Triple powered electrodes are lowered into hot metal in ladle.Electric arc emerges between electrodes to heat and refine the hot metal.The triple electrodes controlling system determines the specific postion of the electrodes according to the preset refining plan.Meanwhile,PLC measures arc current and voltage and compares them with setpoint value to calculate error signal.First,Error signal is rectified by PID controlling strategy.Second,this rectified signal is converted into ±10V voltage signal to control proportional valve's opening direction and amount.Third,the proportional valves will control hydraulic cylinders and the electrodes' position.Follwing this principal,the arc current is adjusted conforming to the refining scheme and the refining effects are optimized and ensured.This study focuses on ladle furnace electrodes position controlling system researching and development.On the one hand,this study designs electro hydraulic proportional controlling system to explore hydraulic system's inherit edges such as easy to interface with automatic controlling system,large power to mass ratio and high precision for position controlling.Vickers' proportional direction valves' are employed in the design.On the other hand,SIEMENS S7-300 series PLC system is employed to control hydraulic system.In terms of controlling algorithm,this study adopts PID rectifying strategy to improve system general performance.Moreover,advanced computer simulation technology is employed to simulate system statistic and dynamic characters.This study builds system model and analyzes Simulink and Amsim simulation results.Then,using PID rectifying strategy,system comprehensive performance is improved specifically.