Method of monitoring the phase state of material in processes involving crystallization from melt and apparatus for performing same

摘要

While monitoring the phase state of a material in processes including crystallization from a melt, a photo-optical system is operated to receive the radiation coming from the material being treated, and the amplitude-frequency spectrum of the output electric signal of the photoreceiver of this system is followed. The presence in this signal of a low-frequency components within a range of from 0.5 to 30 Hz indicates that the optical system is located above the molten portion of the material being treated. To utilize this method for monitoring the position of the interface between the solid and molten zones or phases, there is employed a carriage supporting thereon the photo-optical system and mounted for reciprocation transversely of the interface between the liquid and solid phases. The output of the photoreceiver of the photo-optical system is provided with a frequency-amplitude analyzer including a circuit for inhibiting the permanent component. The drive of the carriage includes a stepping motor connected to the output of the analyzer and adapted to be controlled by the input signals of the latter so that upon the appearance at the output of the analyzer of a signal containing the low-frequency component the carriage is displaced toward the solid phase, whereas upon the absence in the input signal of the low-frequency variable component the said carriage is displaced toward the liquid phase of the material.