Billet Heating with The Homopolar Generator
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Recent and ongoing research concerned with homopolar generators operated in a pulse mode and making use of kinetic energy storage principles has led to the application of these techniques to forging billet heating. Cylindrical billets of AISI-SAE 1022 and 1042 ferritic steels, Type 304 stainless steel, and Type 6061 aluminum were heated to their forging temperatures within 2 to 4 seconds. Although not used during the study, a feedback control system for the generator should make it possible to deliver billets at a uniform temperature. Scale loss with the ferritic steels was less than 0.5 percent. Heating of billets is uniform over their cross sections, which is a unique characteristic of the unidirectional current pulse, and differs fundamentally from almost all other processes, which heat from the surface inward. Energy delivery efficiency of the homopolar pulse billet heating process is insensitive to billet aspect ratio and resistivity. The process appears to be attractive for heating nonmagnetic billets or materials having high resistivities, but would likely be more expensive than induction heating if used to heat ferritic steel billets.