Abstract: An electric arc furnace (1) operated with alternating current has a converter (2) which converts mains voltage (U), into primary voltage (U?) having a furnace frequency (f?). A furnace transformer (4) transforms the primary voltage (U?) into a secondary voltage (U?), supplied to electrodes (6) in a furnace vessel (8) (1). They apply electric arcs (10) to a melt material (9) in the vessel (8). The secondary voltage (U?) is also supplied to a capacitor assembly (7) on the output side of the furnace transformer (4) and the furnace transformer (4) is connected on the output side. A control device (5) controls the converter (2) such that a primary voltage (U?) output from the converter (2) to the furnace transformer (4) has a furnace frequency (f) of least ten times the mains frequency (f) and/or greater than 1 kHz.

Abstract: An electrical arrangement for an electric arc furnace (1) operated with alternating current has a converter (2) which converts mains voltage (U), having a mains frequency (f), of a supply grid (3) into primary voltage (U?) having a furnace frequency (f?). A furnace transformer (4) of the electrical arrangement transforms the primary voltage (U?) into a secondary voltage (U?). The secondary voltage (U?) is supplied to a number of electrodes (6) of the electric arc furnace (1). The electrodes (6) are arranged in a furnace vessel (8) of the electric arc furnace (1). They apply electric arcs (10) to a melt material (9) in the furnace vessel (8). The secondary voltage (U?) is also supplied to a capacitor assembly (7) which is on the output side of the furnace transformer (4) and to which the furnace transformer (4) is connected on the output side.

Abstract: Flicker values to be expected may be determined and achieve a high probability from suitable state and operating variables which are acquired during the first minutes in the initial smelting phase. In this way, flicker can effectively be reduced and kept below predefined limiting values. This is in particular suitable during steel production using electric arc furnaces.

Abstract: In a method for operating an electric arc furnace operated with an alternating voltage, a structure-borne sound signal occurring on a wall of the electric arc furnace is detected, from which structure-borne sound signal a parameter characterizing the flicker properties of the electric arc furnace is calculated. At least one process variable of the electric arc furnace is controlled on the basis of the calculated parameter. An electric arc furnace operated according to the method is used in and for a melting plant.

Abstract: A method for monitoring a vulcanization process of a vulcanization mixture contained in a tool may include using an emitter to emit ultrasonic waves toward a boundary surface between the vulcanization mixture and the tool, wherein boundary surface reflects at least part of the ultrasonic waves. The vulcanization process may be monitored as a function of at least part of the emitted ultrasonic waves reflected by the boundary surface, wherein the ultrasonic waves include at least transverse waves generated by the emitter.

Abstract: A method for controlling a melt process in an arc furnace, including a signal processing component, program code, and data medium for performing the method. Sound signals or vibrations from the interior of the furnace container are captured by solid-borne sound sensors, from which characteristic values can be derived representing the distribution of melting material, melt, and slag in the furnace fill. A characteristic values are generated in priority sequence for: thermal radiation impinging on the furnace wall of the container, the lumpiness of the melting material in the volume of furnace fill, and the change to the portion of solid melting material contacting the furnace wall. The energy distribution at the electrodes is chanced by a control system based on the characteristic values in priority sequence, such that thermal load peaks are dampened or even completely prevented.

Abstract: In a method for determining a state variable of an electric arc furnace, especially for determining the level of the foamed slag (15) in a furnace, the energy supplied to the furnace is determined with the aid of at least one electric sensor while solid-borne noise is measured in the form of oscillations on the furnace. The state variable is determined by a transfer function which is determined by evaluating the measured oscillations and evaluating measured data of the electric sensor. The state of the foamed slag level can thus be reliably recognized and be monitored over time. The foamed slag level is decisive for the effectiveness with which energy is fed into the furnace. Furthermore, losses caused by radiation are reduced by covering the arc with the foamed slag. The improved measuring method allows the foamed slag level to be automatically controlled or regulated in a reliable manner.

Abstract: In a method for operating an arc furnace (2) with at least one electrode (3a, 3b, 3c), a solid material fed to the arc furnace (1) is melted by an arc (1) formed by the at least one electrode (3a, 3b, 3c). A measurement (MM) for the mass of one part of the solid material arranged on a boundary (2) of the arc furnace (1) is determined, and using the determined measurement (MM), a process variable of the arc furnace (1) is controlled and/or regulated. A method which can reduce the risk of electrode damage caused by metal scraps falling into the treated area is provided.

Abstract: Flicker values to be expected may be determined and achieve a high probability from suitable state and operating variables which are acquired during the first minutes in the initial smelting phase. In this way, flicker can effectively be reduced and kept below predefined limiting values. This is in particular suitable during steel production using electric arc furnaces.

Abstract: A method operates a vacuum melting system for metallurgically treating molten steel. A vacuum melting system is operated according to the method. The acoustic signals generated in a ladle which receives the molten steel are detected by at least one structure-borne noise detector which is directly or indirectly acoustically coupled to the ladle, and the acoustic signals are used to ascertain the height or the thickness of the foamed slag which can be found in the ladle over the molten bath of the molten steel.

Abstract: Metallurgical treatment of a steel melt is provided in a vacuum melting system in which acoustic signals generated in a pan receiving the steel melt are recorded with at least one structure-borne sound pick-up acoustically coupled directly or indirectly to the pan. The acoustic signals are used to determine a variable characterizing the operating state of the vacuum melting system.

Abstract: In a method for operating an electric arc furnace operated with an alternating voltage, a structure-borne sound signal occurring on a wall of the electric arc furnace is detected, from which structure-borne sound signal a parameter characterizing the flicker properties of the electric arc furnace is calculated. At least one process variable of the electric arc furnace is controlled on the basis of the calculated parameter. An electric arc furnace operated according to the method is used in and for a melting plant.

Abstract: During operation of an alternating-current electric arc furnace, which has at least one electrode for producing a melt, vibrations are measured at a wall of a furnace vessel, whereby a slag height of the melt is determined. A rapid reaction to the change in the slag height is made possible by adjusting the arc length of the at least one electrode in the case of deviations of a measured actual value of the slag height from a target value.

Abstract: In a method for determining the size and shape value (M) for a solid material (S), in particular scrap metal, in an arc furnace (1), an electrode flow fed to an electrode (3a, 3b, 3c) for forming an arc furnace (L) between the electrode (3a, 3b, 3c) and the solid (S) is measured (30) and from the measured electrode flow (I (t)), an effective measurement value of the electrode flow is determined (31) and from the measured electrode flow (I (t)) (32), a flow part associated with a frequency range of the measured electrode flow is determined (32), and a quotient of the flow part and an effective measurement value is formed as a measurement of the shape and size value of the flow (M). Thus, a method is provided that enables a property of a fusible element introduced into one of the arc furnaces to be determined.

Abstract: In a method, a variable characterising an operational state of an electrode of an arc furnace can be determined. An electrode flow guided to the electrode is detected in the method and the structure-borne noise oscillations are detected. From the detected electrode flow, a flow evaluation signal associated with the frequency range of the detected electrode flow is determined. From the detected structure-borne noise oscillations, an oscillation evaluation signal that is associated with a frequency range of the detected structure-borne noise oscillations is detected and a quotient from the oscillation evaluation signal and the flow evaluation signal is formed as a radiation measurement for at least one frequency common to the detected electrode flow and the detected structure-borne noise oscillation.

Abstract: An electric arc furnace, signal processing device, storage medium, machine-readable program code, and method for determining a time for charging (e.g., recharging) an electric arc furnace with material to be melted (e.g., scrap) are provided. The electric arc furnace may include electrode(s) for heating material inside the electric arc furnace by an electric arc. By detecting a signal for determining a phase state of an electric arc root on the side of the material to be melted based on a captured electrode current, by checking whether the signal exceeds a predetermined threshold value for a predetermined minimum duration, and by ensuring that the charging time is reached at the earliest when the signal exceeds the predetermined minimum duration threshold value, a state-oriented charging time for an electric arc furnace can be determined to reduce energy use, resource use, and production time for a production cycle to reach a tap weight.

Abstract: An arc furnace, a control and/or regulating device for an arc furnace, and a method for operating an arc furnace are provided, wherein an arc for melting metal is generated by at least one electrode, wherein an arc associated with the electrode(s) has a first radiation power based on preselected operating parameters, wherein the arc furnace is operated according to a predefined operating program based on an expected process sequence, wherein monitoring is performed to detect whether an undesirable deviation exists between the actual process sequence and the expected process sequence. Because a modified second radiation power is specified if a deviation is present, and a modified second set of operating parameters, e.g., impedance value(s), is determined based on the modified second radiation power, a method is provided that permits a minimal melting time while minimizing consumption of operating resources, e.g., with respect to arc furnace cooling.

Abstract: A method for controlling a melt process in an arc furnace and signal processing component, program code, and data medium for performing said method are provided. According to the method, sound signals or vibrations from the interior of the furnace container are captured by solid-borne sound sensors, from which characteristic values can be derived for the distribution of melting material, melt, and slag in the furnace fill. A characteristic value SM for thermal radiation impinging on the furnace wall of the container, a characteristic value M for the lumpiness of the melting material in the volume of furnace fill, and a characteristic value MM for the change to the portion of solid melting material contacting the furnace wall are generated in priority sequence. The energy distribution at the electrodes is changed by a control system analyzing the characteristic values in priority sequence, such that thermal load peaks are dampened or even completely prevented.

Abstract: In a method and a device for controlling a carbon monoxide output of an electric arc oven, comprising an oven container, an arrangement for determining a height of a foamed slag in at least three zones of the oven container on the basis of a solid-borne sound measurement, at least one first device for controlling an oxygen infeed, and at least one second device for controlling a carbon infeed into the oven container, the height of the foamed slag is determined in each of the at least three zones and associated with a carbon monoxide content in the exhaust gas of the electric arc oven, wherein the carbon infeed and/or the oxygen infeed in at least one of the at least three zones is controlled such that the height of the foamed slag is maintained below a maximum value.

Abstract: In a melting furnace, a vibration inducer is installed on a furnace vessel, a sensor is arranged opposite or at another place on the furnace vessel and a signal recording and calculation unit is connected to the vibration inducer and the sensor. The melting process can be monitored and the progress of melting can be measured by measuring the signals of the vibration inducement after having passed through the interior of the furnace by this sensor and evaluating the signals of the signal recording and calculation unit. Thus, process-controlled, state-oriented regulation of the melting process can be carried out and the electric arc power is optimally matched to the respective state of the melting process. The signal of the sensor is preferably correlated with the excitation signal of the vibration inducer and/or conclusions are drawn about the melting process by combined evaluation of the vibration inducement and the measured vibration.