US20120152057A1 - Electric arc melting facility and method for producing molten metal by using the electric arc melting facility - Google Patents

Electric arc melting facility and method for producing molten metal by using the electric arc melting facility Download PDF

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Publication number
US20120152057A1
US20120152057A1 US13/392,403 US201013392403A US2012152057A1 US 20120152057 A1 US20120152057 A1 US 20120152057A1 US 201013392403 A US201013392403 A US 201013392403A US 2012152057 A1 US2012152057 A1 US 2012152057A1
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United States
Prior art keywords
source iron
melting
electric arc
chamber
iron
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US13/392,403
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English (en)
Inventor
Yasuki Mikami
Takato Matsuo
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JP Steel Plantech Co
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JP Steel Plantech Co
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Assigned to JP STEEL PLANTECH CO. reassignment JP STEEL PLANTECH CO. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MATSUO, TAKATO, MIKAMI, YASUKI
Publication of US20120152057A1 publication Critical patent/US20120152057A1/en
Abandoned legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5211—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
    • F27B3/10—Details, accessories, or equipment peculiar to hearth-type furnaces
    • F27B3/28—Arrangement of controlling, monitoring, alarm or the like devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D13/00—Apparatus for preheating charges; Arrangements for preheating charges
    • F27D13/002—Preheating scrap
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/144—Power supplies specially adapted for heating by electric discharge; Automatic control of power, e.g. by positioning of electrodes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/02—Details
    • H05B7/144—Power supplies specially adapted for heating by electric discharge; Automatic control of power, e.g. by positioning of electrodes
    • H05B7/148—Automatic control of power
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C2005/5288—Measuring or sampling devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the present invention relates to an electric arc melting facility that produces molten metal by continuously feeding a source iron, such as iron scrap or direct-reduced iron, and melting the source iron by means of an electric arc, and also relates to a method for producing molten metal by using the electric arc melting facility.
  • a source iron such as iron scrap or direct-reduced iron
  • a batch type electric furnace that melts and refines a source iron, such as scrap uses a method of opening a furnace roof arranged on an upper side of the furnace and charging the scrap to be processed into the furnace by using a basket.
  • melting work may be temporarily interrupted. Further, opening the furnace roof may cause a large heat loss and raise dust that adversely affects environment.
  • another type electric furnace has been proposed, which is capable of continuously feeding scrap to a furnace without opening a furnace roof when charging the scrap (see Patent Document 1 and Patent Document 2, for example).
  • FIG. 8 is a schematic diagram showing a configuration of a scrap-continuous-feed type electric furnace (electric arc melting facility 22 ) as proposed in Patent Document 1.
  • a scrap charge port is formed on a side surface of an electric furnace (melting chamber) 1 and is connected to a scrap feeder (source iron feeder) 8 to continuously feed scrap (source iron) 15 into the furnace.
  • FIG. 9 is a schematic diagram showing a configuration of another scrap-continuous-feed type electric furnace (electric arc melting facility 22 ) as proposed in Patent Document 2.
  • a preheating chamber 16 is directly connected to a side surface of an electric furnace 1 and is equipped with a pusher (pushing device) 17 to be inserted into and retracted from the preheating chamber 16 to feed scrap 15 into the electric furnace 1 .
  • the electric furnace of the type that continuously feeds the scrap keeps molten metal in its inside to melt the fed scrap by the energy of the molten metal.
  • Energy to be applied from outside is used for maintaining the temperature of the molten metal, so that the temperature of the molten metal is adjusted to be held at a temperature higher than a melting point of the scrap. Therefore, an important factor of the electric furnace that continuously feeds the scrap is to keep balance between the scrap feed rate and the molten metal temperature, i.e., the energy supplied for melting.
  • Patent Document 3 In a scrap-continuous-feed type electric arc furnace, a total amount of in-furnace molten metal is calculated from a cumulative amount of charged scrap, and is used along with a measured temperature value of the molten metal to accurately estimate the temperature of the molten metal after the scrap is charged. Based on this estimation, the scrap feed rate is controlled so that the temperature of the molten metal falls within a proper temperature range.
  • the in-furnace molten metal amount can be estimated with accuracy to a certain degree, and the speed of a scrap transfer device can be controlled in accordance with the estimated in-furnace molten metal amount.
  • this method has a drawback such that, the state in the electric arc furnace is not actually observed, and so the source iron feed rate and the energy supplied to an electric furnace may not be optimally adjusted.
  • the amounts of molten metal produced therefrom may differ depending on the type of scrap. Therefore, the amount of the in-furnace molten metal estimated by the calculation from the amount of the charged scrap may greatly differ from the actual amount of molten metal in refining. Thus, the estimated temperature of the molten metal may also differ from the actual temperature.
  • the amount of the scrap fed over a long period of time can be estimated, but the amount of the scrap actually fed into the furnace may vary in a short period of time. If a large amount of scrap is fed in a short period of time, the balance with respect to the feed energy for melting may be disordered, and the scrap may be stacked in the furnace. In order to melt the stacked scrap, it is necessary to supply a large amount of energy and also to prolong a melting time. It is thus important to control the scrap charge rate in an appropriate balance with the scrap melting rate in the electric arc furnace so as to smoothly perform melting.
  • An object of the present invention is to solve the problems of the conventional techniques described above for electric furnaces, particularly in a case where an electric arc furnace is used for a melting chamber. Specifically, an object is to provide an electric arc melting facility and a method of operating the electric arc melting facility configured to continuously feed a source iron into the electric arc furnace and melt it therein, while detecting a state change of the source iron fed in the furnace to maintain the molten metal in the electric arc furnace in a stable state.
  • an electric arc melting facility comprising a melting chamber configured to melt a source iron therein by electric arc discharge generated from an electrode, and a source iron feeder configured to continuously feed the source iron to the melting chamber.
  • the electric arc melting facility further comprises a state change detector configured to detect a state change of the melting chamber when the electric arc discharge is generated from the electrode, and a controller configured to adjust a feed rate at which the source iron feeder feeds the source iron to the melting chamber, based on a detection result of the state change detector.
  • the state change of the source iron in the furnace is quickly detected, and the feed rate of the source iron can be adjusted in accordance with the detection result. Accordingly, the molten metal in the electric arc furnace can be maintained in a stable state.
  • the state change detector may be configured to detect a variation in at least one of current and voltage applied to the electrode, as the state change of the melting chamber.
  • a variation in at least one of current and voltage applied to the electrode is used to quickly and indirectly detect the state change of the source iron in the furnace, so that the feed rate of the source iron can be adjusted in accordance with the detection result.
  • the state change detector may be configured to detect a variation in at least one of amounts of harmonics contained in the current and the voltage, as the variation in at least one of the current and the voltage applied to the electrode.
  • a variation in at least one of amounts of harmonics contained in the current and the voltage is used to quickly and indirectly detect the state change of the source iron in the furnace, so that the feed rate of the source iron can be adjusted in accordance with the detection result.
  • the state change detector may be configured to detect a value of or a variation per unit time in at least one of the current and the voltage, as the variation in at least one of the current and the voltage applied to the electrode.
  • a value of or a variation per unit time in at least one of the current and the voltage applied to the electrode is used to quickly and indirectly detect the state change of the source iron in the furnace, so that the feed rate of the source iron can be adjusted in accordance with the detection result.
  • the state change detector may be configured to detect a variation in vibration of the furnace body transmitted to the melting chamber when the electric arc discharge is generated, as the state change of the melting chamber.
  • the state change detector may be configured to detect a variation in position of the electrode as the state change of the melting chamber.
  • a variation in position of the electrode is used to quickly and indirectly detect the state change of the source iron in the furnace, so that the feed rate of the source iron can be adjusted in accordance with the detection result.
  • a method for producing molten metal while melting the source iron by using the electric arc melting facility described above comprises a state change detecting step of detecting a state change of the melting chamber when the electric arc discharge is generated, and a feed rate adjusting step of adjusting a feed rate at which the source iron is fed to the melting chamber, based on a detection result in the state change detecting step.
  • the state change of the source iron in the furnace is quickly detected, and the feed rate of the source iron can be adjusted in accordance with the detection result. Accordingly, the molten metal can be produced while the molten metal in the electric arc furnace is maintained in a stable state.
  • the method for producing the molten metal may further comprises adjusting an electric power applied to the electrode, in addition to the feed rate, based on a detection result by the state change detector.
  • the electric power applied to the electrode of the electric arc furnace is adjusted in addition to the feed rate of the source iron, so that the state of the molten metal can be further stably controlled.
  • the method for producing the molten metal may further comprises a source iron feeding step of driving a pushing device disposed at a lower side of a preheating chamber, which is configured to preheat the source iron therein, to feed the source iron from the preheating chamber to the melting chamber, a source iron preheating step of introducing exhaust gas generated in the melting chamber into the preheating chamber to preheat the source iron in the preheating chamber, and a source iron melting step of melting the source iron with heat generated by the electric arc discharge in the melting chamber while feeding the source iron to the preheating chamber so as to maintain a state in which the source iron is present in the preheating chamber and the melting chamber.
  • the state change of the source iron in the furnace can be quickly detected in an indirect manner. Further, by adjusting an operation condition in accordance with the detection, the molten metal in the furnace can be maintained in a stable state. Accordingly, an operation with high energy efficiency can be performed without prolonging the melting time of the source iron.
  • FIG. 1 This is a flowchart showing a general operation of a method for producing molten metal by using an electric arc melting facility according to an embodiment of the present invention.
  • FIG. 2 This is an explanatory view showing detection of current and voltage harmonics along with a scrap feeder control circuit according to an embodiment of the present invention.
  • FIG. 3 This is an explanatory view showing detection of current and voltage along with a scrap feeder control circuit according to an embodiment of the present invention.
  • FIG. 4 This is an explanatory view showing detection of scrap by using vibration of a furnace body along with a scrap feeder control circuit according to an embodiment of the present invention.
  • FIG. 5 This is an explanatory view showing detection of an electrode position along with a scrap feeder control circuit according to an embodiment of the present invention.
  • FIG. 6 This is a graph showing changes with time in scrap feed rate and harmonic distortion ratio. (An example of the present invention)
  • FIG. 7 This is a graph showing changes with time in scrap feed rate and harmonic distortion ratio. (A comparative example)
  • FIG. 8 This is a schematic diagram showing a conventional scrap-continuous-feed type electric furnace.
  • FIG. 9 This is a schematic diagram showing another conventional scrap-continuous-feed type electric furnace.
  • the state factors include amounts of harmonics contained in current, amounts of harmonics contained in voltage, a variation in current, a variation in voltage, a variation in position of the electrode, and vibration of the furnace body.
  • the following matters have been found: When a source iron is excessively fed into the electric arc furnace and so the source iron is not completely melted but partly remains on the surface of the molten metal near the electrode, generation of electric arc discharge from the electrode of the electric arc furnace to the part of the source iron remaining on the surface of the molten metal can be indirectly detected by detecting the above-described state changes of the melting chamber.
  • the feed rate of the source iron to the electric arc furnace can be adjusted in accordance with the presence or absence of the detection of the electric arc discharge, so that the state in the furnace is maintained stable.
  • changes in state factors that affect changes in the state of the melting chamber are each described as the “a state change of the melting chamber”, wherein the state factors include amounts of harmonics contained in current, amounts of harmonics contained in voltage, a variation in current, a variation in voltage, a variation in position of the electrode, and vibration of the furnace body.
  • FIG. 1 is a flowchart showing a general operation of a method for producing molten metal by using an electric arc melting facility according to an embodiment of the present invention.
  • a source iron is continuously fed to a melting chamber (a source iron feeding step S 11 ), and the source iron is melted by electric arc discharge generated from an electrode (a source iron melting step S 12 ). Then, a state change of the melting chamber when the electric arc discharge is generated is detected (a state change detecting step S 13 ).
  • this embodiment is made to detect a state change of the melting chamber so as to indirectly detect generation of the electric arc discharge to the source iron remaining on the surface of the molten metal.
  • the feed rate for feeding the source iron to the melting chamber is adjusted (a feed rate adjusting step S 14 ).
  • the state change detecting step S 13 measures, as the state change of the electric arc furnace (the melting chamber), at least one of vibration of the furnace body, a variation in position of the electrode, a variation in current, a variation in voltage, amounts of harmonics contained in current, and amounts of harmonics contained in voltage, and detects a change of such a measured value. Then, the feed rate adjusting step S 14 adjusts the feed rate of the source iron by using at least one of a plurality of state changes, or a combination thereof, of the melting chamber detected by the state change detecting step S 13 .
  • the feed rate adjusting step S 14 stops the feed of the source iron to the melting chamber when the state change detecting step S 13 detects, on the basis of a variation in amounts of harmonics, the electric arc discharge generated to the source iron remaining on the surface of the molten metal due to the excessively fed source iron.
  • the feed rate of the source iron may be controlled to be decreased.
  • the detection may preferably be made based on a plurality of detection results from among the above-described respective state changes of the melting chamber.
  • the amount of a harmonic contained in current or voltage is preferably used because detection is easily carried out and a change is detected properly.
  • the amount of a harmonic is given based on harmonics obtained through frequency analysis on a result of measurements of current or voltage fed to the electric arc furnace, and may be used in a form of a harmonic distortion ratio.
  • An example of the electric arc melting facility used in the present invention comprises an electric arc furnace, a source iron feeder that continuously feeds a source iron to the electric arc furnace, a detector for a state change of a melting chamber, and a controller that adjusts the feed rate of the source iron feeder by using an output from the detector.
  • the detector for a state change of the melting chamber is a device that can detect a generation of the electric arc discharge from an electrode of the electric arc furnace to the source iron fed into the electric arc furnace.
  • the electric power applied to the electric arc furnace may be adjusted instead of the control on the feed rate of the source iron.
  • the arc electric power is increased without the feed rate being changed, a source iron newly fed needs to be melted in addition to melting of the source iron already present in the furnace. In this case, a large electric power is required, and thereby makes it impossible to attain an operation with high energy efficiency, which is an object of the present invention.
  • the present invention may be applied to an electric arc melting facility of the type as described in Patent Document 2, which comprises a melting chamber configured to melt a source iron therein, a shaft-type preheating chamber directly connected to the melting chamber and configured to preheat the source iron to be fed to the melting chamber, an electrode disposed in the melting chamber to melt the source iron fed in the melting chamber, and a pushing device disposed at a lower side of the preheating chamber and configured to move the source iron, fed from the preheating chamber, toward the electrode.
  • Patent Document 2 which comprises a melting chamber configured to melt a source iron therein, a shaft-type preheating chamber directly connected to the melting chamber and configured to preheat the source iron to be fed to the melting chamber, an electrode disposed in the melting chamber to melt the source iron fed in the melting chamber, and a pushing device disposed at a lower side of the preheating chamber and configured to move the source iron, fed from the preheating chamber, toward the electrode.
  • the present invention can be applied to an operation of melting the source iron by electric arc heating in the melting chamber, while introducing exhaust gas generated in the melting chamber into the preheating chamber to preheat the source iron in the preheating chamber, and feeding the source iron to the melting chamber so as to maintain a state in which the source iron is present in the preheating chamber and the melting chamber.
  • a control mechanism is provided to a driving device of the pushing device to control the feed rate of the source iron.
  • the source iron is fed by using the pushing device, and so the pushing device needs to be returned to the pushing start position each time when the pushing operation is completed. That is, the feed is not necessarily performed in a completely continuous manner. However, even when the feed is not necessarily performed in a completely continuous manner but repeatedly performed at predetermined intervals, the feed of the source iron to the electric arc furnace is regarded as a continuous operation.
  • a not-continuous-feed means a feed performed in a manner that the source iron is, for example, collectively dropped by using a basket etc. like a batch feed, and the feed cannot be stopped in the middle of a single feed of the source iron to the electric arc furnace after it is once started.
  • the source iron is an object, such as iron scrap or direct-reduced iron, to be subjected to the melting process in the electric arc melting facility.
  • the iron scrap includes, for example, stainless steel scrap, pig iron, mill scales, or rerollable scrap.
  • the iron scrap is generated, for example, when steelmaking or other processes are performed by steelmakers, when processes using iron products are performed in factories, or when buildings, automobiles, electrical appliances, bridges, etc., are knocked down.
  • FIG. 2 is an explanatory view showing a general configuration of an electric arc melting facility according to a first embodiment of the present invention, and shows a case in which the state of scrap inside a furnace is detected by using harmonics in current or voltage applied to electric arc melting.
  • an electric sensor 12 ( 12 a , 12 b , and 12 c ) serving as a state change detector for detecting a state change of a melting chamber 1 is connected to a power feed line 11 ( 11 a , 11 b , and 11 c ) extending to an electric arc furnace 1 , to measure a current waveform or a voltage waveform of the power feed line 11 .
  • the measured waveform is subjected to Fourier transform by a signal processor 13 to calculate harmonics contained therein, and the result is input to a controller 6 as a signal-processed state signal 14 ( 14 a , 14 b , and 14 c ). If the source iron is excessively fed in the furnace and comes to be present near an electrode, an electric arc is generated from the electrode to the source iron, and the harmonics in current or voltage are caused to vary. If the signal-processed state signal 14 has a value or a variation per unit time not smaller than a predetermined value, the controller 6 sends a control signal 7 to a scrap feeder 8 , which serves as a source iron feeder, to decrease the scrap feed rate or to stop the feed. Then, if the measurement value is decreased to another predetermined value, the controller 6 sends a control signal 7 to the scrap feeder 8 to increase the scrap feed rate to a predetermined rate.
  • a harmonic distortion ratio is preferably used as the signal-processed state signal 14 .
  • the harmonic distortion ratio is continuously measured, and two threshold values (harmonic judgment values) are set such that a higher threshold value serves as a harmonic judgment value H and a lower threshold value serves as a harmonic judgment value L.
  • the harmonic judgment value H is set to such a value that the harmonic distortion ratio exceeds the harmonic judgment value H if an abnormal event occurs during melting of the source iron in the electric arc furnace such that the source iron comes to be present near the electrode.
  • the harmonic judgment value L is set to such a value that the harmonic distortion ratio falls below the harmonic judgment value L if melting of the source iron progresses and the furnace comes to have a flat bath state therein.
  • the source iron feed rate is controlled to be decreased if the harmonic distortion ratio exceeds the harmonic judgment value H, and increased if the harmonic distortion ratio falls below the harmonic judgment value L. Consequently, even if an abnormal event occurs such that the source iron is excessively fed into the furnace, the state is immediately restored to a normal state, and the production of molten metal can be continued in a stable state.
  • FIG. 3 is an explanatory view showing a general configuration of an electric arc melting facility according to a second embodiment of the present invention, and shows a case in which the state of scrap inside a furnace is detected by using current or voltage applied to electric arc melting.
  • an electric sensor 12 ( 12 a , 12 b , and 12 c ) serving as a state change detector for detecting a state change of a melting chamber 1 is connected to a power feed line 11 ( 11 a , 11 b , and 11 c ) extending to an electric arc furnace 1 , to measure current or voltage of the power feed line 11 .
  • a state signal 5 ( 5 a , 5 b , and 5 c ) of the electric sensor 12 is input to a controller 6 . If the current or voltage of the power feed line 11 has a value or a variation per unit time not smaller than a predetermined value, the controller 6 sends a control signal 7 to a scrap feeder 8 , which serves as a source iron feeder, to decrease the scrap feed rate or to stop the feed. Then, if the measurement value is decreased to another predetermined value, the controller 6 sends a control signal 7 to the scrap feeder 8 to increase the scrap feed rate to a predetermined rate.
  • FIG. 4 is an explanatory view showing a general configuration of an electric arc melting facility according to a third embodiment of the present invention, and shows a case in which the state of source iron inside a furnace is detected by using vibration of a furnace body.
  • an acceleration sensor 4 (a state change detector) serving as a state change detector for detecting a state change of a melting chamber 1 is attached to an electric arc furnace body (a melting chamber) 1 .
  • the acceleration sensor 4 continuously measures vibration of the furnace body, and inputs a state signal 5 of the vibration to a controller 6 . If the source iron is excessively fed into the furnace and comes to be present near an electrode, an electric arc is generated from the electrode to the source iron, and vibration of the furnace body is caused to vary.
  • the controller 6 sends a control signal 7 to a scrap feeder 8 , which serves as a source iron feeder, to decrease the scrap feed rate or to stop the feed. Then, if the measurement value is decreased to another predetermined value, the controller 6 sends a control signal 7 to the scrap feeder 8 to increase the scrap feed rate to a predetermined rate. Consequently, the state in which the source iron is excessively fed into the furnace is immediately resolved and a stable operation can be continued.
  • FIG. 5 is an explanatory view showing a general configuration of an electric arc melting facility according to a fourth embodiment of the present invention, and shows a case in which the state of scrap inside a furnace is detected by using a variation in position of an electrode.
  • an electrode position detector 9 serving as a state change detector for detecting a state change of a melting chamber 1 is attached to a movable portion of an electrode elevator 3 for the electrode.
  • the electrode position detector 9 continuously measures an electrode position, and inputs a result signal to a controller 6 . If the source iron is excessively fed into the furnace and comes to be present near the electrode, an electric arc is generated from the electrode to the source iron, and variations in current and voltage become large.
  • the controller 6 sends a control signal 7 to a scrap feeder 8 , which serves as a source iron feeder, to decrease the scrap feed rate or to stop the feed. Then, if the measurement value is decreased to another predetermined value, the controller 6 sends a control signal 7 to the scrap feeder 8 to increase the scrap feed rate to a predetermined rate.
  • the melting state of the source iron is controlled by changing the source iron feed rate, but the state of molten metal can be controlled in a more stable manner by further adjusting the electric power applied to the electric arc furnace in addition to the feed rate.
  • each of amounts of harmonics contained in current, amounts of harmonics contained in voltage, a variation in current, a variation in voltage, vibration of the furnace body, and a variation in position of the electrode can be individually used for detecting the state of the source iron.
  • a combination of two or more of them may be used, so that the scrap state is figured out more correctly and the state in the furnace can be stabled more reliably.
  • a variation in the electric arc current is used along with the amount of harmonics contained in the electric arc current to detect the scrap state.
  • a melting test for iron scrap was performed by using the electric arc melting facility shown in FIG. 2 .
  • FIG. 6 shows an example in which the harmonics in current fed to the electrode were measured and the scrap feed rate was changed in the method for producing molten metal by using the electric arc melting facility according to the first embodiment described above.
  • the scrap was fed to the electric arc furnace at a constant rate and a harmonic distortion ratio was obtained by a harmonic analyzer disposed at each measurement point of the electric arc current.
  • the harmonic distortion ratio represents a percentage of the sum of effective values of all generated harmonics with respect to an effective value of a reference frequency.
  • the present example is configured to determine that scrap comes to be present near the electrode inside the furnace, when the harmonic distortion ratio exceeds a predetermined value (the harmonic judgment value H), and to stop the scrap feed. As the scrap inside the furnace is increased, the harmonic distortion ratio is also increased. If the scrap feed is stopped when the value exceeds the harmonic judgment value H (time “a” in FIG. 6 ), the scrap melting progresses and the harmonic distortion ratio is caused to be gradually decreased.
  • the decrease in harmonic distortion ratio represents a state in which an electric arc is generated to molten metal and the scrap is not present near the electrode any more.
  • the scrap feed is restarted at a predetermined rate. In this way, the state change inside the furnace was quickly detected, and the state was immediately restored to a normal state, so that the scrap melting was continued.
  • FIG. 7 shows a comparative example relative to the present invention, and shows a case in which the scrap feed rate is not changed even if a harmonic distortion ratio of the electric arc current is increased. If the present invention is used, the scrap feed is stopped or decreased in feed rate at a time “a” in FIG. 7 . However, since the scrap was continued to be fed, the scrap amount in the furnace was increased, and the harmonic distortion ratio was increased, so that this state was being continued. That is, the scrap was not completely melted and kept remaining. Since the operation was continued under this condition, an excessive amount of energy was required, and a melting time was also greatly prolonged. Consequently, the energy efficiency was lowered, and the productivity was deteriorated.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Power Engineering (AREA)
  • Environmental & Geological Engineering (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Discharge Heating (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Furnace Details (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US13/392,403 2009-08-27 2010-08-23 Electric arc melting facility and method for producing molten metal by using the electric arc melting facility Abandoned US20120152057A1 (en)

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JP2009-196451 2009-08-27
JP2009196451 2009-08-27
PCT/JP2010/064659 WO2011024982A1 (ja) 2009-08-27 2010-08-23 アーク溶解設備および当該アーク溶解設備を用いた溶湯の製造方法

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US11384986B2 (en) 2017-03-31 2022-07-12 Hatch Ltd. Open arc condition mitigation based on measurement

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EP2471959A1 (en) 2012-07-04
JP2011069606A (ja) 2011-04-07
CN201828130U (zh) 2011-05-11
CN102003875A (zh) 2011-04-06
WO2011024982A1 (ja) 2011-03-03
TWI401405B (zh) 2013-07-11
KR20120064684A (ko) 2012-06-19

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