Transformer-driven shield for electromagnetic casting

#The present invention relates to an improved process and apparatus for casting metals and alloys, particularly copper and copper alloys, utilizing an active transformer-driven shield. Electromagnetic casting of metals and alloys has been known and used for many years.

#Known electromagnetic casting apparatus comprises a three part mold consisting of a water cooled inductor, a non-magnetic screen, and a manifold for applying cooling water to a forming ingot. Such an apparatus is exemplified in U.S. Pat. No. 3,467,166 to Getselev et al. Containment of the molten metal is achieved without direct contact between the molten metal and any component of the mold. Solidification of the molten metal is achieved by direct application of water from the cooling manifold to the ingot shell.

#The prior art in electromagnetic containment and casting of molten metal generally discloses the use of an alternating magnetic field of an inductor to provide a means of inducing electromagnetic pressure within the primary casting area for containing molten metal. The electromagnetic pressure effected in the prior art is controlled to counterbalance the variable metallostatic pressure through the use of non-magnetic shields or screens, such as those exemplified by U.S. Pat. Nos. 3,646,988, 3,773,101, 3,605,865, 3,985,179, 3,467,166, 3,741,280, 4,004,631, 3,702,155, and 3,735,799. These shields act to attenuate the magnetic field generated by the primary inductor in such a way as to maintain vertical or near vertical side walls in the liquid, especially in the vicinity of the solid-liquid interface. These shields are normally positioned above the liquid-solid interface and at least partially between the inductor and the molten metal. Currents are induced within the shield to an extent which depends on the shield's electrical impedance. The shield itself can be considered as a counter inductor.

#FIG. 1 is a schematic representation of a prior art electromagnetic casting apparatus.

#FIG. 2 is a schematic representation of an electromagnetic casting apparatus in accordance with the present invention, showing an auxiliary power source attached to the shield.

#FIG. 3 is an electrical schematic of an electromagnetic casting system in accordance with the present invention.

#Referring now to FIG. 1, there is shown therein a prior art electromagnetic casting apparatus. The electromagnetic casting mold 10 is comprised of an inductor 11 which is water cooled; a cooling manifold 12 for applying cooling water to the peripheral surface 13 of the metal being cast C; and a non-magnetic shield 14. Molten metal is continuously introduced into the mold 10 during a casting run using a trough 15 and a downspout 16 and conventional molten metal head control. The inductor 11 is excited by an alternating current from a power source 17.

#The alternating current in the inductor 11 produces a magnetic field which interacts with the molten metal head 19 to produce eddy currents therein. These eddy currents in turn interact with the magnetic field and produces forces which apply a magnetic pressure to the molten metal head 19 to contain it so that it solidifies in a desired ingot cross section.

#An air gap d exists during casting between the molten metal head 19 and the inductor 11. The molten metal head 19 is formed or molded into the same general shape as the inductor 11 thereby providing the desired ingot cross section. The inductor may have any desired shape including circular or rectangular as required to obtain the desired ingot C cross section.