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
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
• • 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
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/06—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated
  • F27B9/062—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated electrically heated
  • F27B9/067—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated electrically heated heated by induction
• • 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
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/60—Continuous furnaces for strip or wire with induction heating
• • 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
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/14—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity characterised by the path of the charge during treatment; characterised by the means by which the charge is moved during treatment
• • 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
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/28—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity for treating continuous lengths of work
• • 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
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories or equipment specially adapted for furnaces of these types
  • F27B9/36—Arrangements of heating devices
• • 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
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/562—Details
  • C21D9/565—Sealing arrangements
• • 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 generally to electric induction tunnel furnaces where continuous strips or discrete plates pass through a gas-sealed tunnel to be inductively heated, and in particular to such furnaces when used in processes where protection against leakage of the process gas from the tunnel to atmosphere must be accommodated.
• strip 90 passes through electric induction gas-sealed tunnel furnace 110.
• Furnace enclosure 112 is made sufficiently gas-tight around the tunnel 114 through which strip 90 passes.
• Electric induction coil 116 (or coils) can be placed outside of enclosure 112 if the enclosure is sufficiently transparent to the magnetic flux field that is generated by alternating current flowing through coil 116 and allows the field to penetrate inside of the enclosure so that the field can magnetically couple with the strip in the tunnel.
• Thermal insulation 118 can be utilized, for example, between the interior of the tunnel and enclosure 112.
• the flux field heats the strip by electromagnetically coupling with the strip to induce eddy currents in the strip.
• the strip is heated to perform an industrial process, for example, if the strip is coated with a liquid composition before entry into the tunnel, inductive heating of the strip will cause the liquid composition to bond (or cure) to the strip by evaporation of solvents in the liquid composition.
• the inductive heating in the furnace must be accomplished in a process gas environment that could be problematic if the tunnel gas is released into the open air (atmosphere) around the outside of the furnace for reasons such as pollution, explosive or combustive reaction with air, high cost of the process gas, or strict low tolerance to deviations in the composition of the process gas.
• the process gas in the tunnel for decarburization of steel comprises a high concentration hydrogen gas.
• enclosure 112 may be called a "gas-tight" enclosure, the enclosure is subject to leakage since, practically, the enclosure can not be constructed as a single continuous enclosure without the cost being prohibitive. Therefore .
• joints between materials making up the enclosure that may be sufficiently gas-tight during initial fabrication of the enclosure, but may leak after the furnace is put into operation, for example, as a result of repeated heating and cooling of the materials around the joint.
• the enclosure composition and thermal insulation themselves may be gas permeable and serve as passages for gas leaks from the tunnel.
• One method of handling tunnel gas leaks is to allow the leaking tunnel gas to escape into a well ventilated atmosphere.
• forced ventilation box 180 can be placed around the exterior of furnace 110. Top openings 180a in the ventilation box provide a directed release of gas from the ventilation box when fan 182 forces surrounding external air through the ventilation box.
• such method lacks a precise means of insuring that dangerous concentrations of process gas do not build up in the atmosphere exterior to the furnace.
• the present invention is an apparatus for, and method of, performing an electric induction heating process on a continuous strip or discrete plates passing through a substantially gas-tight tunnel furnace
• the tunnel is formed by an enclosure extending along the longitudinal length of the furnace from the strip entry end, to the strip exit end of the furnace.
• a barrier chamber or plenum is formed around the longitudinal length of the exterior of the enclosure.
• a barrier gas can be injected into the barrier chamber and maintained at a pressure different from the pressure of the process gas in the tunnel.
• the inductors used in the induction heating process may be located outside of the barrier chamber or within the barrier chamber.
• the present invention is an electric induction gas-sealed tunnel furnace.
• a furnace enclosure forms a closed tunnel region along the longitudinal length of the furnace enclosure through which a workpiece passes through for induced heating.
• the closed tunnel region of the furnace enclosure has a workpiece entry end and a workpiece exit end.
• a furnace enclosure entry end flange is located at the workpiece entry end, and a furnace enclosure exit end flange is located at the workpiece exit end.
• An induction coil is disposed around the longitudinal length of the closed tunnel region of the furnace enclosure.
• a barrier material forms a gas-tight barrier chamber around the exterior of the longitudinal length of the furnace enclosure, with the . . barrier material having a sealed entry end interface with the furnace enclosure entry end flange and a sealed exit end interface with the furnace enclosure exit end flange.
• the present invention is a method of preventing a process gas leak from an electric induction gas-sealed furnace that has a furnace enclosure forming a closed tunnel region along the longitudinal length of the furnace enclosure through which a workpiece passes through for induced heating while the process gas is contained at least within the closed tunnel region.
• the closed tunnel region of the furnace enclosure has a workpiece entry end and a workpiece exit end.
• An entry end flange is located at the workpiece entry end of the furnace enclosure, and an exit end flange is located at the workpiece exit end of the furnace enclosure, with an induction coil disposed around the longitudinal length of the furnace enclosure.
• a barrier material is provided around the exterior of the longitudinal length of the furnace enclosure, and a gas-tight chamber is formed around the exterior of the longitudinal length of the furnace enclosure by sealing an entry end interface between the barrier material and the furnace enclosure entry end flange, and sealing an exit end interface between the barrier material and the furnace enclosure exit end flange.
• the present invention is a method of electric induction heat treatment of a workpiece in a process gas within a closed tunnel region formed within the longitudinal length of a furnace enclosure.
• the workpiece is fed through an entry end flange at a workpiece entry end of the closed tunnel region, with the entry end flange forming a sealed entry end interface with a barrier material located exterior to furnace enclosure.
• An alternating current is supplied to an induction coil disposed around the longitudinal length of the furnace enclosure to inductively heat the workpiece in the closed tunnel region.
• the workpiece is withdrawn from the closed tunnel region through an exit end flange at a workpiece exit end of the closed tunnel region, with the exit end flange forming a sealed exit end interface with the barrier material, thereby forming a gas-tight barrier chamber around the exterior of the longitudinal length of the furnace enclosure into which chamber a barrier gas is supplied.
• FIG. 1 is a cross sectional view of a prior art electric induction gas-sealed tunnel furnace.
• FIG. 2(a) is a longitudinal cross sectional view of one example of an electric induction gas-sealed tunnel furnace of the present invention.
• FIG. 2(b) is a transverse cross sectional view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 2(a) through line A-A.
• FIG. 2(c) is a partial top elevation view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 2(a) through line D-D.
• FIG. 3(a) is a cross sectional view of another example of an electric induction gas-sealed tunnel furnace of the present invention.
• FIG. 3(b) is a transverse cross sectional view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 3(a) through line B-B.
• FIG. 3(c) is a partial top elevation view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 3(a) through line E-E.
• FIG. 4(a) is a cross sectional view of another example of an electric induction gas-sealed tunnel furnace of the present invention.
• FIG. 4(b) is a transverse cross sectional view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 4(a) through line C-C.
• FIG. 4(c) is a partial top elevation view of the electric induction gas-sealed tunnel furnace of the present invention shown in FIG. 4(a) through line F-F.
• FIG. 5(a) and FIG. 5(b) illustrate alternate ways of gas-sealing the workpiece entry and exit ends of an electric induction gas-sealed tunnel furnace of the present invention.
• FIG. 6 is one example of a barrier gas control system used with an electric induction gas-sealed tunnel furnace of the present invention.
• FIG. 2(a), FIG. 2(b) and FIG. 2(c) illustrate one example of an electric induction gas-sealed tunnel furnace 10 of the present invention.
• barrier . . chamber 20 is formed around the outer longitudinal surface of enclosure 12 by joining barrier material 22 to suitable longitudinal end structural elements of enclosure 12.
• the end structural elements are "U" shaped entry and exit end flanges 12a that are suitably connected to each longitudinal end of furnace enclosure 12, for example, by welding or bolted connections. Similar connecting means can be used to join barrier material 22 to flanges 12a.
• inlet conduit 24 is provided for supply of the barrier gas to the barrier chamber.
• the term "longitudinal” as used herein is the length of the furnace's enclosure from strip entry end (adjacent to the arrow in FIG. 2(a)) to strip exit end. Therefore barrier chamber 20 forms a "wrap around" substantially gas-tight chamber exterior to furnace enclosure 12 for the length of the furnace from strip entry end to strip exit end.
• enclosure 12 forms an interior longitudinal "sleeve” around the transverse of the tunnel and barrier material 22 forms an exterior longitudinal second “sleeve” around the transverse of the closed tunnel region, where the term “transverse” as used herein refers to tunnel cross sections substantially perpendicular to the length of the strip moving through the tunnel.
• gas-tight barrier chamber is bounded by the exterior of furnace enclosure 12; interior of the barrier material 22; and the two longitudinal exit and entry end flanges 12a of the enclosure 12.
• Flanges 12a can be considered an integral part of enclosure 12 in the present invention, and represent one non-limiting method of terminating the longitudinal ends of the enclosure.
• Flange 12a at one longitudinal end of the furnace can extend completely around the perimeter of the tunnel workpiece entry and/or exit.
• One or more inductors 16 can be located exterior to enclosure 12 and barrier material 22, if the enclosure and barrier material are formed from an electromagnetically transparent material such as siliconized or teflonized glass fabric, for example in a sheet form.
• thermal insulation 18 can be provided in all examples of the invention.
• the single turn solenoidal inductor used in the example can be connected to an external alternating current power source (via inductor load matching components if used) at terminals 16a and 16b.
• the inductor may be one or more inductors that may be connected in any electrical configuration, for example, in series and/or parallel, and may be of any suitable type for a particular application, such as a solenoidal or transverse flux inductor. . .
• a barrier gas for example an inert gas such as nitrogen, can be injected into barrier chamber 20 via inlet conduit 24 to a positive barrier gas pressure that is greater than the pressure of a process gas in gas-tight tunnel 14 during strip processing in the tunnel.
• One or more outlet conduits can be provided to withdraw barrier gas from the barrier chamber.
• Gas-tightness at the entry and exit to the tunnel of the furnace in all examples of the present invention can be achieved either by interconnection to other components in the strip industrial process as shown in FIG. 5(a), or by making the entry and exits ends of the furnace sufficiently gas-tight as shown in FIG. 5(b).
• the immediate interconnecting entry and exit gas-tight components may be stainless steel flanges 80, and upstream or downstream components connected to the stainless steel flanges can handle supply and return of the process gas to and from the tunnel of the furnace.
• FIG. 5(a) the immediate interconnecting entry and exit gas-tight components may be stainless steel flanges 80, and upstream or downstream components connected to the stainless steel flanges can handle supply and return of the process gas to and from the tunnel of the furnace.
• FIG. 3(a), FIG. 3(b) and FIG. 3(c) illustrate another example of an electric induction gas-sealed tunnel furnace 30 of the present invention.
• the barrier chamber is an enlarged barrier plenum 34 formed around the outer longitudinal surface of furnace enclosure 12 by joining barrier material 32 to suitable longitudinal end structural elements of enclosure 12.
• the end structural elements are "U" shaped entry and exit end flanges 12a that are suitably connected to each longitudinal end of the enclosure, for example, by welding or bolted connections.
• Similar connecting means can be used to join barrier material 32 to flanges 12a.
• inlet conduit 36 is provided for supply of the barrier gas to the barrier chamber. Therefore barrier plenum 34 forms a "wrap around" substantially gas-tight chamber exterior to furnace enclosure 12 for the length of the furnace from strip entry end, to strip exit end similar to that for the above example in FIG. 2(a) except that in the present example of FIG. 3(a) inductor 16 is contained within the barrier plenum.
• Barrier plenum 34 is at least sufficiently large to contain the one or more inductors 16 (and fluid cooling elements if used) in the barrier plenum, as opposed to being exterior to the barrier plenum, for example in FIG. 2(a). With this arrangement gas-tight electrical (and fluid cooling if used) fittings must be used for connection to an inductor external electric power source (and cooling source if used).
• end flanges 12a can be considered an integral part of enclosure 12 in the present invention, and represent one . . non- limiting method of terminating the longitudinal ends of the enclosure. Alternatively flanges 12a may be considered an integral part of barrier material 32.
• a barrier gas for example an inert gas such as nitrogen, can be injected into barrier plenum 34 via inlet conduit 36 to a positive barrier gas pressure that is greater than the pressure of a process gas in gas-tight tunnel 14 during strip processing in the tunnel.
• One or more outlet conduits can be provided to withdraw barrier gas from the barrier chamber.
• barrier material 32 is an electrically conductive material
• barrier plenum 34 is sufficiently sized so that the barrier material does not interfere with the path of the magnetic flux field that is generated when alternating current flows through inductor 16. If the barrier material is formed from a non-electrically conductive material, the barrier plenum may be smaller;
• an electromagnetic shield may be required around the smaller non-electrically conductive material.
• FIG. 4(a), FIG. 4(b) and FIG. 4(c) illustrate another example of an electric induction gas-sealed tunnel furnace 40 of the present invention.
• barrier chamber 44 is formed around the outer longitudinal surface of furnace enclosure 12 by joining ends 12' and 12" of furnace enclosure 12 between enclosure entry and exit end flanges 12b and ends 42' and 42" of barrier material 42 together as shown in FIG. 4(a).
• Barrier material ends, enclosure ends, and enclosure flanges may be jointed together by suitable means, such as nut and bolt fasteners. At least at one location, as shown, for example, in the longitudinal cross section in FIG. 4(a) and in partial top view in FIG.
• inlet conduit 46 is provided in barrier material 42 for supply of the barrier gas to the barrier chamber. Consequently gas-tight barrier chamber 44 is bounded by the exterior of furnance enclosure 12 and the interior of the barrier material 42. End flanges 12b can be considered an integral part of furnace enclosure 12 in the present invention, and represent one non- limiting method of terminating the longitudinal ends of the enclosure.
• a barrier gas for example an inert gas such as nitrogen, can be injected into barrier chamber 44 via inlet conduit 46 to a positive barrier gas pressure that is greater than the pressure of a process gas in gas-tight tunnel 14 during strip processing in the tunnel.
• One or more outlet conduits can be provided to withdraw barrier gas from the barrier chamber.
• Supplemental barrier gas can be optionally injected into furnace regions exterior to the barrier chamber depending on the particular arrangement of the barrier chamber. For example in . .
• thermal insulation 18 is typically a gas porous material. Consequently process gas in tunnel 14 may leak through insulation 18, and then through the connected joint between end flange 12b and furnace enclosure 12 at enclosure end 12" as shown in FIG. 4(a). Since this joint would leak to atmosphere and not to the barrier chamber for the particular arrangement shown in FIG. 4(a), barrier gas may be injected into conduit 48 to flood the joint region with the barrier gas.
• FIG. 6 is one example of a simplified barrier gas control system that can be used with some examples of the invention.
• Valve V-l controls barrier gas supply to barrier gas regulator BGR, which regulates the flow of gas to the barrier chamber (20, 34 or 44 in the above examples of the invention) at a nominal barrier gas pressure, which is at a higher positive pressure than the pressure of the process gas in the tunnel in this example.
• Pressure sensor PS senses the actual pressure of the barrier gas in the barrier chamber (or the differential pressure between the gas in the barrier chamber and the process gas in the tunnel) and feeds the sensed pressure data back to the barrier gas regulator BGR.
• Pressure controller PC also senses the actual pressure of the barrier gas in the barrier chamber (or the differential pressure between the gas in the barrier chamber and the process gas in the tunnel).
• Valve V-2 is an optional control valve for gas supplies to the pressure sensor and pressure controller.
• Valve V-3 can be provided at an optional gas outlet from the barrier chamber, for example, to cool down the barrier gas chamber by a continuous flow (or
• Valve V-3 may be connected to barrier gas processing equipment not shown in the drawing.
• One example of an application of an electric induction gas-sealed tunnel furnace of the present invention is for the decarburization of strip steel.
• the process gas contained in the tunnel comprises a high percentage of hydrogen gas that would burn or explode in air. Therefore the process gas in the tunnel must be maintained at a pressure greater than the atmospheric pressure surrounding the furnace to avoid air penetration into the tunnel.
• the inert barrier gas selected for this example is standard industrial grade nitrogen that is injected into the barrier chamber of the furnace to a pressure greater than the process gas pressure so that any leak between the enclosure of the furnace and the barrier chamber will cause the flow of nitrogen into the tunnel, rather than the flow of process gas into the barrier chamber. . .
• the barrier gas may be acceptably reactive with the process gas in tunnel. That is the chemical reaction between a non-inert barrier gas and the process gas does not result in combustion, explosion or other hazardous condition.
• the barrier gas supplied to the barrier chamber may be either a re-circulating gas or a non-re-circulating gas.
• Re-circulating gas may be used, for example, to capture and process leaking process gas from the tunnel in the event that the positive pressure differential between the barrier gas in the barrier chamber and the process gas in the tunnel is lost, or if it is necessary to cool down the barrier chamber, or regions adjacent to the barrier chamber, by a continuous flow of barrier gas through the barrier chamber.
• location of the barrier gas inlet to the barrier chamber or plenum may be located in other convenient locations as required for a particular application.
• barrier chamber Although one barrier chamber is shown in the examples of the invention, multiple barrier chambers may be used in other examples of the invention depending upon a particular application.
• pressure of the barrier gas in the barrier chamber or plenum is greater than the process gas in the tunnel, in other applications the pressure differential my be reversed with the barrier gas in the barrier chamber or plenum being at a lower pressure than the process gas in the tunnel.
• the forced air ventilation box shown in FIG. 1 may be used in combination with an electric induction gas-sealed tunnel furnace of the present invention as an additional feature.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Combustion & Propulsion (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Furnace Details (AREA)
• Tunnel Furnaces (AREA)
• General Induction Heating (AREA)

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• 2011
  • 2011-05-24 EP EP11787235.8A patent/EP2577201B1/en active Active
  • 2011-05-24 KR KR1020127033388A patent/KR101822496B1/ko active Active
  • 2011-05-24 JP JP2013512147A patent/JP6192536B2/ja active Active
  • 2011-05-24 CN CN201180026034.2A patent/CN103069243B/zh active Active
  • 2011-05-24 US US13/114,493 patent/US9400136B2/en active Active
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