Abstract: A mold structure for casting large metallic parts such as ingots so as to avoid the formation of the "shrinkage pipe" which normally develops on the exposed top surface of such castings during their solidification comprises a cap for placement on a mold which includes a diaphragm having a front surface located to intercept radiation emitted from the top surface of the cooling metal mass and to re-emit radiation back thereto, and a reflector for returning radiation emitted from the back surface of the diaphragm such as an infrared reflector or a stack of baffles. The cap may include a cooler for cooling the reflective surface and suitable ports which allow the interior of the mold and cap to be evacuated. Portions of the mold adjacent its open top may be provided with insulation to prevent heat loss from the metal by conduction. A heater for providing make-up heat to the top surface of the metal mass may also be included in the structure.

Abstract: Energy efficient reheating furnaces and soaking pits having essentially zero thermal inertia are disclosed.The furnace comprises an evacuate chamber having a workpiece support, an envelope having a highly infrared reflective interior surface bounding the chamber, and a workpiece heating means comprising electric leads and contacts for heating the workpiece by electrical resistance and/or a cryogenically cooled induction coil located outside of the envelope for heating the workpiece by eddy current dissipation. A workpiece on the support is thermally isolated since convective heat losses are eliminated, conductive heat losses minimized, and radiative heat losses limited to about 10 percent or less of the workpiece's black body radiative flux. Since radiation emitted by the workpiece does not reach the induction coil, the design allows the application of cryogenic-superconductivity technology which eliminates eddy current losses in the coil.