Abstract: A direct current electric arc furnace hearth connection of the liquid-solid type is initially installed as a metal billet in an opening in a furnace construction, with water-containing refractory material rammed around the billet. When the material dries and with the furnace in operation, a melt in the furnace, which the billet must contact, with incidental melting of the inner end of the billet, cannot escape around the billet, the outer end of the billet being cooled and remaining solid to form an electrical connection for operation of the furnace.

Abstract: A DC arc furnace having a hearth through which electric power can be transmitted to a melt formed on the hearth to form a positive connection permitting the arcing electrode or electrodes to be negatively connected to a DC power source, to operate as a cathode with improved operational characteristics, is made with its hearth enclosure having one or more permanent openings required for the normal operation of any arc furnace, this opening being exemplified by a deslagging port through which slag is removed by tilting the furnace in the direction of the port.

Abstract: The present invention relates to a device in direct current arc furnaces with a furnace vessel and at least one arcing electrode (cathode) and at least one contact electrode. The number of cathodes and/or contact electrodes (for example hearth connections - anodes) may be one, two or more.

Abstract: A DC arc furnace of the type having an arcing electrode and a withdrawable starting electrode for initially forming electrical contact with a charge of metal pieces, and an electric connection for a subsequently formed melt in the furnace, has a DC power source positively connected directly with the starting electrode and the melt connection, and negatively connected with the arcing electrode. When initially charged with solid metal pieces, the starting electrode is contacted with the charge so that an arc is formed between the pieces and the arcing electrode until a melt is formed for contact with the connection for the melt. With both the starting electrode and melt connection directly connected positively with the power source, without intervening control equipment, the current automatically commutates from the starting electrode to the melt connection as the melt forms so as to contact the latter.

Abstract: An electric arc furnace for DC operation has an electric connection for a melt in the furnace's hearth, in the form of an elongated metal connector having a refractory enclosure exposing an inner end of the connector for contact with and incidental melting by the melt, with means for cooling the connector between its inner and outer ends and removing heat at a rate preventing the connector from melting throughout its length to its outer end. The connector has a cross-sectional area large enough to carry the current required for forming a heating arc between an electrode and the surface of the melt, and the connector has similar composition as the melt as exemplified by a steel connector for a steel melt.

Abstract: A DC arc furnace has a hearth formed with an extension in which a melt-contact electrode is positioned, and has an arcing electrode laterally spaced from this contact electrode. This results in the formation of an arc that is oblique in a direction facing away from the contact electrode. To prevent the arc from being excessively destructive with respect to the furnace vessel's side wall toward which the arc was directed, furnace charging material, in particulate form, is continuously fed to a melt in the furnace, as a flow directed into the arc foot spot formed by the oblique arc, resulting in a maximum efficiency of energy absorption of the normally cold charging material and at the same time, via the charged material, shading the lining of the furnace vessel from an attack by the arc.

Abstract: An electric arc furnace has an anodic contact or hearth electrode and a cathodic arcing electrode, and the furnace is rotative about its vertical axis while the arcing electrode remains stationary in its lateral direction. With a melt in the furnace, the DC arc can be directed in different angular directions with respect to the inside of the furnace.