CONTINUOUS CASTING OF FINE GRAIN INGOTS

Continuous Casting of Fine Grain Ingots In the representative embodiment described in the specification, continuous casting of fine-grain ingots is effected by supplying molten metal (24) to a mold (25) in which the metal is solidified and an ingot (26) is withdrawn downwardly and controlling the temperature in the central region of the molten metal above the ingot at a level at which small crystallites (34) of metal are formed, but large quantities of solid material are not formed. The desired temperature level may be maintained by visual observation of the surface of the metal or pyrometric detection of the temperature of the surface and control of a directional energy input device (31) such as an electron beam gun or a plasma torch to supply sufficient energy to maintain the desired temperature level. The typical apparatus described in the specification includes a cold hearth (10) containing a pool (21) of molten metal which is supplied to the mold and energy input devices (14, 15), which may be electron beam guns or plasma torches, for melting the material in the hearth and maintaining the temperature of the molten material in the hearth and the mold at the desired levels, along with temperature detectors (28, 35) for detecting the temperature of the molten metal in the hearth and the mold, and a control unit (18) for controlling the energy input devices for the hearth and the mold (Fig. 1).