PURPOSE: To scan an electron beam zigzag in the radial direction of a billet and to shorten the melting time by deflecting the X and the Y axis scanning currents in which phases of waveforms are different from each other in the directions being orthogonal to each other, allowing them to work on the electron beam and also increasing and decreasing repeatedly the amplitude of both the scanning currents.
CONSTITUTION: At the time of putting a billet 28 of casting quantity of once into a melting use container and melting the billet 28 by irradiating its surface with an electron beam 30, when an X axis deflecting current IX and a Y axis deflecting current IY of the same frequency wavelength being orthogonal to each other are given to this electron beam 30 by shifting each frequency wavelength phase by 90°, the electron beam is scanned by drawing a circular track by its resultant current. In this state, the amplitude of both the scanning currents IX, IY is increased and decreased repeatedly plural times in the course of one rotation of the electron beam 30, the electron beam 30 is brought to circular motion, while executing a zigzag motion in the radial direction, therefore, the electron beam 30 scans uniformly the surface of the billet 28, and the melting time is shortened.
UNO MOTOMU
SHIRABE TETSUMI
OBA HIROYOSHI
