ELECTROMETALLURGICAL RELATIONSHIPS IN ELECTRIC SMELTING FURNACES

摘要

For over 100 years the electric arc furnace was mainly a smelting tool. Comparatively recently it has developed into a multi-functional, quick-melting, machine with pre-treatment of the charge, oxy-fuel burners, and procedures for producing foamy slag. New mechanical features have been added, such as the Eccentric Bottom Tapping (Ebt), a feature that assures improved metallurgy and pouring practice and reduced angle of tilt to below 15°. The application of water cooling to the furnace shells and cover also resulted in improved refractory performance. Each of these features have their counterparts in SAF practice, where some of them originated, such as, pretreatment of the charge. A still unfolding development concerns power management and control techniques that were developed at SAF installations where the power supply comprised three single-phase transformers. This arrangement enabled a fixed level ofmthe reaction zone leading to a step improvement of furnace power control. As a result, the electrode holders could be maintained in a stationary mode, while the electrodes themselves could be slipped to match consumption. The power is regulated at each phase by changing the tap settings on the individual transformers. This practice, since it frequently involved an upgrade in instrumentation, made it possible to diagnose conditions deep within the furnace burden ― especially the relative contributions of arc-and Joule-power. The goal now is to control the partitioning of the applied power since arc-power represents radiant energy and Joule power is developed within the charge and mainly below the tips of the electrodes - two different forms of energy supply..