AUTOMATIC CONTROL METHOD FOR THROWING RAW MATERIAL IN VACUUM MELTING FURNACE

PURPOSE:To obtain homogeneous ingots, by calculating the finite difference of the practical throwing amount to the target throwing amount in each short period and throwing the total amount of the practical throwing amount and the finite difference in the next specified period. CONSTITUTION:A consuming electrode 3 is melted by arc discharge in a vacuum melting furnace 1 to form a electric melting pond 4 and is moved downward by a downward shifting unit 2 according to the consumed amount of the electrode. The grain raw material in a hopper 5 is side-charged through an electromagnetic feeder 6 and a throwing shoot 7. At this time, the weight of the raw material remaining in the hopper 5 and the electromagnetic feeder 6 is measured continuously by a load cell 8, and the downward shifted distance of the consuming electrode 3 is measured from hour to hour by a stroke-meter 10 and these measured values are inputted to a control part 9. The control part 9 calculates the finite difference between the input value and the target value, and orders the electromagnetic feeder 6 to throw the total amount of the finite difference and the throwing amount of this time in the next specified period, and the raw material is always thrown in a constant rate into the melting pond 4.