CONTROLLED SOLIDIFICATION OF CASE STRUCTURES BY CONTROLLED CIRCULATING FLOW OF MOLTEN METAL IN THE SOLIDIFYING INGOT

摘要

Continuously casting an ingot wherein the ingot has a pool of molten metal extending downstream a substantial distance from the casting mold, entrained by an outer skin of the ingot formed during passage through the mold. The molten metal within the pool is continuously circulated along the solid/liquid interface advantageously for at least a major portion thereof in a first direction the same as that of ingot movement and is returned in an opposite direction within the interior of the pool. This sweeping flow of metal along the interface changes the solidification microstructure from that which would be normally present, and results in the formation of improved and advantageously new products, e.g., new steel bodies, particularly noted by unique microstructures. The flow rate is chosen to provide a variety of novel solidification structures, i.e., modified equiaxed dendritic structure, or structures herein described as thamnitic of fibrous structures, within the ingot. The circulation of the molten metal may be provided by a helical coil which extends about the ingot downstream from the mold and, in the optimum arrangement, for substantially the entire extent of the molten pool within the ingot.