Abstract: The invention provides a direct current electric arc furnace which is composed of a feeding system of direct current to the furnace, a movable electrode at the roof of the furnace, and a bottom electrode attached to the bottom of the furnace at the position deviated from the center of the bottom of the furnace, the deviated distance from the center being determined by a magnetic field, generated by a current in the steel bath of the furnace, from under an arc generated by the movable electrode to the bottom electrode, which can cancel a second magnetic field generated by the current of the feeding system.

Abstract: A flicker compensating apparatus for compensating for flickering due to a variation in the reactive power generated from a DC arc furnace connected by an AC/DC converter to an AC power system, comprises: a current detector for detecting a DC current flowing in the DC arc furnace; a controller for determining the phase control angle of a thyristor included in the AC/DC converter in accordance with the difference between the detected DC current and a predetermined reference current; a calculator for calculating reactive power to be generated by the DC arc furnace, from the detected DC current, the determined phase control angle, and a no-load DC voltage; a compensator including a reactive load connected via thyristor to the power system; and a controller for controlling the phase control angle of the thyristor of the compensator in accordance with the calculated reactive power, for controlling a current flowing across the reactive load, and for permitting the compensator to generate such reactive power as to co

Abstract: A direct current electric arc furnace comprises a main body, a moving electrode attached at the center of a roof of the furnace which generates an arc under the moving electrode, a bottom electrode attached at the center of the bottom, conductors which are connected to the bottom electrode, so that the deviation of the arc caused by a magnetic field originated at the outside of the main body is cancelled by another magnetic field caused by the conductors when electric currents are fed to the conductors and means of feeding direct currents to the conductors.

Abstract: The invention provides a direct current electric arc furnace which is composed of a feeding system of direct current to the furnace, a movable electrode at the roof of the furnace, and a bottom electrode attached to the bottom of the furnace at the position deviated from the center of the bottom of the furnace, the deviated distance from the center being determined by a magnetic field, generated by a current in the steel bath of the furnace, from under an arc generated by the movable electrode to the bottom electrode, which can cancel a second magnetic field generated by the current of the feeding system.

Abstract: System for controlling the positions of each of the three electrodes of a three phase electric furnace to maintain optimum real power delivered to the furnace in the event of electrode short circuiting or arc extinction due to scrap movement in the furnace. The system includes means for determining the magnitude of arc voltage and arc current and means to change the position of selected electrodes when either arc voltage or arc current is determined to be zero.

Abstract: A method of controlling the course over time of a target temperature of a molten metal in a ladle, for example, in which the required heating power is produced by at least one plasma torch. Determination is made of the variation with time of a target temperature, the mass of an outwardly flowing melt, and a specific heat value of the melt present in the ladle. From the foregoing values there is ascertained the course of a corresponding setting signal for obtaining the heating power necessary to obtain the desired temperature course. Simultaneously and continuously the actual temperature of the melt is measured. When the actual temperature of the melt deviates from its target temperature in excess of a predetermined tolerance, the setting signal for the heating power is changed by decreasing such setting when an actual temperature exceeds the target temperature, and increasing such setting when an actual temperature is less than the target temperature.

Abstract: According to this process and this device:a signal representing the derivative of the intensity of the current in the arc is sensed,the sensed signal is amplified,the amplified signal is directed simultaneously into two band pass filters (6, 7) respectively having a high frequency broad band (6) and having a narrow band centered on a low fundamental frequency (7),the signals emanating from the filters (6, 7) are transmitted to effective value extractors (8, 9),by means of a divider module (11) an energy signal is formulated, which is proportional to the ratio of the effective value of the signal emanating from the broad band filter (6) and the effective value of the signal emanating from the narrow band filter (7),and the proportional energy signal obtained is displayed on a scale (12), where it is expressed as a percentage, this percentage being indicative of the behaviour of the arc, signifying the formulation phase.

Abstract: An induction melting apparatus including a vessel for holding a melt of molten metal, an induction coil operatively associated with the vessel, and a power supply for providing power input to the induction coil. The power input has a melting component at a first preselected frequency for operatively holding the melt at a preselected temperature by induction heating and an agitation component at a second preselected and different frequency for agitation of the melt by inducing turbulence therein. The power supply comprises an agitation power supply circuit operatively supplying current to the coil at the second frequency, and a melting power supply circuit including a series resonant circuit through which the melting component is operatively applied to the coil at the first frequency at the same time as the agitation component is applied to the coil.

Abstract: An electric reduction furnace with a furnace vessel having a refractory lining and electrodes which are connected to a three-phase current power supply unit and which extend into the furnace vessel. In the region between, in each case, two first electrodes (21-22, 22-23, 23-21) and the wall of the furnace vessel, additional second electrodes (31-33) ae provided which form with each two of the first electrodes substantially isosceles triangles. The additional second electrodes (30-33) extend substantially parallel to the first electrodes (21-23) and are electrically connected to the furnace lining (14).

Abstract: A DC arc furnace comprising a furnace vessel having a hearth and a side wall extending upwardly from the hearth, conductive means for conducting DC through the hearth from its outside to a melt in the hearth, an arcing electrode, a substantially horizontal arm having a holder holding the electrode substantially vertically above the hearth, a substantially vertical mast from which the arm extends, and means for connecting DC positively to the conductive means and negatively to the electrode so as to form an arc between the electrode and the melt and producing an arc flare to which the side wall is exposed; wherein the improvement comprises means for connecting the arm to the mast so as to permit the arm to be adjustably moved longitudinally to different positions and means for mounting the mast so it can be adjustably rotated to different positions about its axis, whereby the electrode and its arc can be located at different positions horizontally to the side wall.

Abstract: A direct-current arc furnace has a vessel with a floor and a cover, at least two vault electrodes projecting down into the vessel through the cover, and a hearth electrode exposed in the vessel generally in the floor below the vault electrodes. A scrap-metal charge is melted in this furnace by first energizing the vault electrodes with direct-current voltage of opposite polarity while displacing them downward through the charge from an upper position spaced relatively far from the hearth electrode to a lower position spaced relatively close to the hearth electrode and thereby passing an electric current through the charge to melt the charge and form a puddle of molten metal on the floor of the vessel at the hearth electrode.

Abstract: An electrode for arc furnaces, comprising a metallic water-cooled upper section and a consumable, replaceable lower section, interconnected by means of a threaded nipple or the like. At least one light-receiving element is positioned in a zone associated with the interconnection of the cooled metal shaft and the consumable section. A light signal falling on the light-receiving element where the consumable section is in absence, is passed in a suitable manner via a light wave guide to a furnace control which activates a safety system.

Abstract: This invention relates to an electric-arc fired blast furnace system for the reduction of iron-bearing material utilizing electric-arc heated air containing a reducing gas or carbon-containing fuel allowing for a decrease in the amount of coke normally used in the reduction process. The excess reducing gases exiting the furnace are utilized as a source of power via a system consisting of turbines, compressors and a heat exchanger to drive the electrical generators which are used to provide electricity to the arc heaters. This arrangement forms an essentially closed loop furnace system for metal reduction. Injection of finely-divided coal into the arc-heated air to provide reductants is also employed.

Abstract: The present invention relates to a structure of neutral point of multiphase transformers for large secondary currents. Such multiple phase transformers, usually three phase transformers, are used for example for the operations of arc furnaces, and the secondary current of the transformer may amount to several thousand ampere. The neutral point is made as a plate (24) of material with good electric conductivity and is located within the transformer tank (27). Between the neutral point plate (24) and the tank wall (27) there is located a plate (25) of a material with good conductivity and serving as a screen for reducing losses in the tank wall (screen plate). The transformer is star connected on the secondary side. Each phase of the secondary winding consists of several windings connected in parallel, and the tappings are passed as parallel conductors onto the neutral point plate (24).

Abstract: In order to assure a high arc current and a high arc power with simultaneous reduction of flicker voltages, at least two juxtaposed electrodes, each having the same distance from the vertical axis of the furnace and the same electrical potential, are connected to each phase of an electric arc furnace, which is preferably a three-phase electric arc furnace. Preferably circular electrodes are employed which are conductively connected together at least in the vicinity of the electric arc.

Abstract: The invention concerns a vacuum arc melting and casting furnace comprising a vacuum chamber, a tilting crucible and a current connection leading to the bottom of the tilting crucible. This current connection consists of a fixed contact and of a co-operating contact arranged on the bottom of the crucible and movable with the tilting crucible. Also provided is an electrode rod for holding an electrode concentrically in relation to the tilting crucible.The fixed contact is secured on at least two current conductors which are substantially coaxial with the electrode rod or electrode. These conductors pass through the vacuum chamber from the top and extend past the tilting crucible, and their distance apart is such that the crucible can be tilted between them into the casting position.

Abstract: A rectangular metallurgical furnace is provided with at least six electrodes which are symmetrically arranged in two rows along the longitudinal axis of the furnace. Each pair of electrodes form a single phase circuit. A transformer is also provided for each pair of electrodes to form bifilar conductor leads. The spacing between adjacent and opposite electrodes is adjusted to provide a continuous bath surface over a maximum horizontal cross section. Adjacent and opposite pairs of electrodes are located in the corners of imaginary squares.

Abstract: Electric arc furnace, of the type having metallic walls (2) and an at least partly metallic roof (1), and provided with radiation detection apparatuses (8) for their controlled operation. Differential water circulation transducers (8) are positioned in the intrados of the metallic part (7) of the roof (1); they project with respect to the inner surface of the roof and their end faces (16) facing the interior of the furnace are concave.

Abstract: At least one arc furnace and at least one induction furnace are connected to the same AC network, the induction furnace being connected via a controllable alternating voltage converter so as to permit compensation of active power fluctuations in the network caused by operation of the arc furnace and the induction furnace being designed to contain scrap for its inductive preheating before charging in the arc furnace.

Abstract: A method for smelting charge materials in an electric arc furnace consists in that a bath of the electric arc furnace is loaded with the charge materials, electrodes of the electric arc furnace are supplied with an alternating current, the charge materials are melted, redox reactions are conducted and a finished melt and a slag are tapped, the alternating current of industrial frequency supplied to the electrodes of the electric arc furnace being first converted to one of a frequency ranging between 0.05 and 30 Hz. An apparatus for carrying into effect the above method comprises an electric arc furnace, in a bath of which are inserted electrodes. A secondary winding of a transformer is coupled with the electrodes through power supply arrangements.

Abstract: A current shunt in the power supply to an electric furnace generates a signal voltage proportional to furnace current. A voltage rate comparator senses a high change rate of signal level corresponding to arcs occurring in the furnace and the comparator output pulse is fed to a preset counter. The counter is reset periodically. If a predetermined number of pulses are registered by the counter within a preset time interval, the counter output will de-energize an output relay which turns the power supply off and energizes a warning signal.

Abstract: A steel treatment system includes a ladle having a cover, a heating electrode mounted to extend through an opening in the cover, a casing surrounding the electrode and including lower, intermediate and upper sections, and a seal mounted at the cover about the opening for forming a seal with the lower section of the casing. A clamp device is mounted on the intermediate section of the casing and extends therethrough for clamping the electrode and for fixing the relative axial position of the electrod with respect to the casing. An actuator is fixedly supported at a level above the clamp device and is operatively connected to the casing to move the casing and the electrode downwardly. First guide rollers act on the lower section of the casing, and second guide rollers act on the upper section of the casing for ensuring axial movement of the casing and electrode.