METHOD AND DEVICE FOR CONTROLLING CASTING PRESSURE IN LOW PRESSURE CASTING MACHINE

摘要

PURPOSE:To cast a molten metal into a die always under the prescribed pressure by changing the change gradient of the voltage impressed to the electromagnetic pump to the change gradient necessary for obtaining the prescribed casting pressure after the thrust of the molten metal discharged from the electromagnetic pump to a specified level to the change gradient necessary for obtaining the prescribed casting pressure then applying the voltage to the electromagnetic pump. CONSTITUTION:The molten metal in a holding furnace 1 is discharged from the electromagnetic pump 3 and is thrusted in a pouring pipe 8. The differential temp. in a temp. sensor 10 decreases gradually when the molten metal approaches the sensor 10. The signals are constantly inputted from the sensors 9, 10 to a means 13 for calculating the level of the molten metal which calculates the voltage impressed to the pump 3 and impresses the same to the pump 3 during this time. The change gradient of the voltage impressed to the pump 3 is changed to the size at which the thrust of the molten metal stops once at the point of the sensor 11 when the thrusting molten metal passes the point of the sensor 10. The molten metal is stopped once at the point of the sensor 11 according to such change. The change gradient of the voltage impressed to the pump 3 is changed to the size at which the molten metal is cast into a die 4 under the desired pressure when the signal from the sensor 11 point is inputted via the means 13 to a means 14 for calculating the electromagnetic pump output. The product of the desired quality is thus cast into the die.