Classifications

• • 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
  • F27B11/00—Bell-type furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/663—Bell-type furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/663—Bell-type furnaces
  • C21D9/673—Details, accessories, or equipment peculiar to bell-type furnaces
• • 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
  • F27D7/00—Forming, maintaining, or circulating atmospheres in heating chambers
  • F27D7/06—Forming or maintaining special atmospheres or vacuum within heating chambers
• • 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
  • F27D99/00—Subject matter not provided for in other groups of this subclass
  • F27D99/0001—Heating elements or systems
  • F27D99/0033—Heating elements or systems using burners

Definitions

• the invention relates to a method for high-temperature annealing of metal strip, sheet metal or wire, in particular of grain-oriented electrical steel in the form of coils in a hot space under inert gas or in a protective gas atmosphere in a hood furnace with a stove with at least one parking space for a batch in the form of a coil or a coil stack, with at least one protective cover which covers the charge and under which the glow space is formed, with a dynamic seal between the hood and stove and with a protective hood at a distance surrounded heating hood, under which a boiler room is formed. Furthermore, the invention relates to a corresponding bell annealing furnace.
• the process for high temperature annealing or coarse grain annealing of grain oriented electrical steel is an annealing process at very high temperatures, such as between 1100 ° C and 1200 ° C.
• Grain-oriented electrical steel is used for the iron core or wound cores of
• Transformers or generators used It is silicon-alloyed steel sheet, which has good magnetic properties.
• the electrical steel is wound into batches or coils or stacked.
• a bell annealing furnace usually has a stove with at least one parking space for a batch in the form of a coil or a coil stack, a protective cover covering the batch, a heating hood and a cooling hood, which is used as an alternative to the heating hood. Under the guard, a glow space is formed.
• the heating hood defines a heating space, which is designed essentially as an annular space between the protective hood and the heating hood.
• the annealing space is purged with nitrogen (N 2 ) to remove the atmospheric oxygen. It is then heated to a temperature of 600 to 850 ° C and possibly held for several hours. During this time, it is purged with nitrogen. When rinsing becomes continuous or at specified intervals inert gas introduced into the annealing space, while the inert gas atmosphere flows with a defined volume flow.
• nitrogen N 2
• the annealing space is rinsed with a mixture of nitrogen (N2) and hydrogen (H2).
• the annealing space or the electrical steel is slowly heated further.
• the purge is switched to pure hydrogen (H2).
• H2 is heated with adjustable gradient, d. H. the temperature is lowered to 650 ° C and below.
• the hydrogen (H2) in the annealing space under the protective hood is flushed out with nitrogen (N2).
• the heating hood can be removed.
• the protective hood is sealed off from the hearth by means of a dynamic seal, in particular one or more sand cups. Although such a gasket is not gas-tight, it is used in practice because of the high annealing temperatures.
• Dome annealing furnaces where the protective hood is sealed off from the stove with a dynamic seal, usually with a sand cup, have hitherto only been electrically heated.
• the electric heating causes comparatively high heating costs.
• Against a heating of the boiler room with burners speaks that oxygen-containing atmosphere from the boiler room can possibly get into the hydrogen-filled space under the protective hood, which is a security problem and also affects the batch.
• the invention has for its object to overcome the disadvantages of the prior art.
• combustion air is supplied to the burners for combustion of the hydrogen, which can escape from the annealing space through the dynamic seal in the boiler room. Since the flames of the burners are openly directed into the boiler room, the hydrogen can be easily rendered harmless.
• the combustion air required for the combustion of the hydrogen can be supplied to the burners by means of a combustion air line, which opens into the boiler room. Alternatively, the combustion air flow to the burners can be increased.
• the overpressure between the annealing chamber and heating chamber during the annealing process is continuously monitored and initiated at a drop in overpressure depending on the falling below a threshold emergency rinsing.
• the quality of the dynamic seal or sand cup seal is continuously monitored during the annealing process.
• the purge rate in the annealing space can be increased.
• the gas flow is increased, which is introduced continuously or at predetermined intervals during the annealing process in the annealing space.
• the emergency purging can be initiated during the entire annealing process to remove hydrogen-containing inert gas atmosphere from the annealing chamber and the boiler room.
• the annealing space and the heating space are each flushed with an inert gas volume flow, wherein the ratio of the inert gas volume flow, with which the heating space is purged under the heating hood, to the inert gas volume flow, with which the annealing space is purged, larger than 25.
• the flames of the burner are directed into the boiler room in such a way that an equidirectional annular flow of the exhaust gases is generated in the boiler room over its entire height. This achieves a uniform temperature distribution.
• the heating hood has a plurality of operated with a liquid or gaseous fuel burners whose flames are open in the boiler room and that in the annealing chamber an overpressure relative to the boiler room is maintained, the at least 10 Pa and at most 200 Pa.
• a development is characterized by at least one group of vertically stacked burners.
• the end faces of the heating hood are each a group of vertically stacked burners, which are directed in the flow direction of the exhaust gases against each other, such that a co-current exhaust gas flow is formed in the boiler room. It is generated in the same way annular flow of exhaust gases in the boiler room over its entire height. Due to the annular flow of the exhaust gases and the good circulation of the exhaust gases of the vertically stacked burner a good temperature uniformity over the entire height of the bell annealing furnace is achieved.
• the burners are designed as high-speed burners.
• the crucible annealing furnace according to the invention is equipped with an emergency flushing device for flushing the heating chamber and the annealing space with inert gas, wherein in the annealing space under the protective hood and the heating chamber under the heating hood each open an inert gas supply.
• the emergency flushing device ensures that a fuel-fired bonnet furnace, whose combustion chamber is not gas-tight against the stove, can be safely operated.
• FIG. 1 is a schematic plan view of a crucible annealing furnace
• Fig. 2 is a schematic front view of a crucible annealing furnace according to the
• Fig. 3 is a diagram with a Not Whytechnisch according to the invention.
• Fig. 1 and Fig. 2 show schematically a heating hood 1 of a bell annealing furnace.
• the heating hood 1 is heated by means of two groups of burners 2 in the form of high-speed burners, preferably recuperative burners.
• the burners 2 of each group are arranged one above the other at the end faces of the heating hood 1 and burn with open flames in a substantially annular heating chamber 3.
• the arrangement of the burner groups takes place against each other to a good sense of exhaust gas flow a good circulation of the flue gases and thus to achieve a good temperature uniformity.
• the burners 2 are supplied with additional combustion air for combustion of the hydrogen material which escapes from the combustion space 5 through the dynamic seal into the heating space 3. Since the flames of the burner 2 are directed open in the boiler room 3, the hydrogen can be made harmless in a simple manner.
• the annealing spaces 5 can be flushed with hydrogen.
• the sand cups are not gas-tight. Hydrogen, which passes through the sand cup seal in the heating chamber 3, is burned by means of excess air to the burners 2, which is dosed appropriately.
• an inert gas supply 6 an emergency flushing device for simultaneous flushing of the heating chamber 3 and the annealing chamber 5 with inert gas, in this case nitrogen.
• the heating chamber 3 is flushed with a large volume of inert gas and at the same time, in each case, the glaciers 5 are flushed with a small volume of intergas.
• FIG. 3 the Notêtmaschinevention is shown.
• the diagram shows the inert gas volume flow (ordinate, in n / h) and the hydrogen and oxygen concentration in% as a function of time (abscissa, in min).
• the lower explosive limit of hydrogen is set at 2%.
• the boiler room 3 is filled with air under the heating hood 1, in the heating chamber 5 under the protective hoods 4 is pure hydrogen.
• Each of the three glaciers 5 under the protective hoods 4 is flushed with 2 rrf / h of nitrogen, the heating chamber 3 under the heating hood 1 with 240 rrf / h.
• the process temperature should be 400 ° C, the gases expand accordingly and thus speed up the flushing process.
• the maximum hydrogen concentration in the heating hood is less than 2% and is reached after approx. 10 min.
• the oxygen content is also about 2%.
• the rinsing of the glaze chambers under the protective hoods 4 is continued until the hydrogen is also rinsed below the protective hoods 4 to less than 2%, which in the present Example after approx. 360 min is reached.
• This heating mantle 1 and 4 protective covers are in safe condition and the emergency flushing is terminated.
• the combustion air can be preheated by means of a central recuperator.
• the burners 2 the combustion air required for the combustion of the combustion air can be supplied by means of a combustion air duct, which opens into the heating chamber 3.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Articles (AREA)
• Furnace Details (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)

Priority Applications (2)

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Publications (1)

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Citations (8)

• 2010
  • 2010-10-06 EP EP10784250.2A patent/EP2486157B9/de active Active
  • 2010-10-06 PL PL10784250T patent/PL2486157T3/pl unknown
  • 2010-10-06 WO PCT/EP2010/006097 patent/WO2011042164A1/de active Application Filing
  • 2010-10-06 TR TR2018/02112T patent/TR201802112T4/tr unknown

Patent Citations (8)

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