EP4023985A1 - Wärmebehandlungsofen - Google Patents

Wärmebehandlungsofen Download PDF

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Publication number
EP4023985A1
EP4023985A1 EP20859246.9A EP20859246A EP4023985A1 EP 4023985 A1 EP4023985 A1 EP 4023985A1 EP 20859246 A EP20859246 A EP 20859246A EP 4023985 A1 EP4023985 A1 EP 4023985A1
Authority
EP
European Patent Office
Prior art keywords
quenching
oil
heating chamber
heat treatment
treatment furnace
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20859246.9A
Other languages
English (en)
French (fr)
Other versions
EP4023985A4 (de
Inventor
Shinichi Takahashi
Kiichi Kanda
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kanto Yakin Kogyo Co Ltd
Original Assignee
Kanto Yakin Kogyo Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kanto Yakin Kogyo Co Ltd filed Critical Kanto Yakin Kogyo Co Ltd
Publication of EP4023985A1 publication Critical patent/EP4023985A1/de
Publication of EP4023985A4 publication Critical patent/EP4023985A4/de
Pending legal-status Critical Current

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    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/58—Oils
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C21D1/63—Quenching devices for bath quenching
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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
    • C21D9/0056—Furnaces through which the charge is moved in a horizontal straight path
    • 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
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • 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
    • F27B9/02—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity of multiple-track type; of multiple-chamber type; Combinations of furnaces
    • F27B9/021—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity of multiple-track type; of multiple-chamber type; Combinations of furnaces having two or more parallel tracks
    • F27B9/025—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity of multiple-track type; of multiple-chamber type; Combinations of furnaces having two or more parallel tracks having two or more superimposed tracks
    • 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
    • F27B9/04—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity adapted for treating the charge in vacuum or special atmosphere
    • F27B9/045—Furnaces with controlled atmosphere
    • 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
    • F27B9/04—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity adapted for treating the charge in vacuum or special atmosphere
    • F27B9/045—Furnaces with controlled atmosphere
    • F27B9/047—Furnaces with controlled atmosphere the atmosphere consisting of protective gases
    • 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
    • F27B9/068—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 heated by radiant tubes, the tube being heated by a hot medium, e.g. hot gases
    • 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
    • F27B9/20—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 the charge moving in a substantially straight path tunnel furnace
    • F27B9/24—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 the charge moving in a substantially straight path tunnel furnace being carried by a conveyor
    • 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
    • F27B9/20—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 the charge moving in a substantially straight path tunnel furnace
    • F27B9/24—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 the charge moving in a substantially straight path tunnel furnace being carried by a conveyor
    • F27B9/243—Endless-strand conveyor
    • 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 peculiar to furnaces of these types
    • F27B9/32—Casings
    • F27B9/34—Arrangements of linings
    • 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
    • F27D7/00—Forming, maintaining, or circulating atmospheres in heating chambers
    • F27D7/06—Forming or maintaining special atmospheres or vacuum within heating chambers
    • F27D2007/063—Special atmospheres, e.g. high pressure atmospheres

Definitions

  • the present invention relates to a heat treatment furnace and particularly to a heat treatment furnace for quenching.
  • a heat treatment furnace for quenching has been known in which a converted gas with a fuel (butane or the like) and air as raw materials is used as an in-furnace atmospheric gas, when performing bright heating for preventing formation of a modified layer at a surface due to oxidation, decarburization, cementation, or the like during quenching heating of steel as a workpiece (see, for example, PTL 1).
  • a heat treatment furnace including a gas supply section configured to supply a neutral gas or an inert gas to a quenching heating chamber, and an internal structure in the quenching heating chamber that is at least partially made from a graphite-based material.
  • a muffle made of a graphite-based material is provided so as to isolate a space in which a workpiece is conveyed from heating means.
  • a belt for conveying a workpiece into the quenching heating chamber may be a conventional heat-resistant metal belt, but may preferably be made from a graphite-based material.
  • a muffle defining at least a part of a dropping space for a workpiece to drop into a quenching oil tank disposed on a downstream side of the quenching heating chamber may be made of a graphite-based material, but may preferably be made of a material that is other than the graphite-based material and that has at least a predetermined level of oxidation resistance performance.
  • the heat treatment furnace further includes oil flow-in preventing means configured to prevent flowing-in of oil from the quenching oil tank on the downstream side of the quenching heating chamber into the quenching heating chamber.
  • the oil flow-in preventing means include a fluid curtain forming section configured to form a fluid curtain between the quenching heating chamber and the quenching oil tank.
  • the fluid curtain forming section include an oil curtain forming device configured to form an oil curtain between the quenching heating chamber and the quenching oil tank, and an oil accepting section provided between the quenching heating chamber and the quenching oil tank so as to accept the oil curtain. It is favorable that the oil accepting section be connected to the quenching oil tank and includes a foam restraining section.
  • the heat treatment furnace further include an oil smoke treating device configured to treat oil smoke in the dropping space for a workpiece to drop into the quenching oil tank on the downstream side of the quenching heating chamber.
  • the heat treatment furnace further includes a fluid curtain forming section configured to form a fluid curtain between the quenching heating chamber and a quenching tank on the downstream side of the quenching heating chamber.
  • FIG. 1 A schematic configuration of a part of a heat treatment furnace 10 according to a first embodiment of the present invention is depicted in FIG. 1 .
  • the heat treatment furnace 10 includes a quenching heating chamber 12 and a quenching oil tank 14.
  • the quenching oil tank 14 is provided on a downstream side of the quenching heating chamber 12. As is clear from FIG. 1 , the quenching oil tank 14 is located below the quenching heating chamber 12 in a vertical direction. It is to be noted that, although not illustrated in FIG. 1 , the heat treatment furnace 10 includes a tempering heating chamber on the downstream side of the quenching oil tank 14.
  • the quenching heating chamber 12 is provided therein with a mesh belt conveyor 16 as conveying means, or a conveying device, for conveying workpieces W.
  • a mesh belt 18 of the mesh belt conveyor 16 is an endless belt, and is wound around a first roller 20, a second roller 22, and the like.
  • the mesh belt 18 can be moved in a circulating manner within the quenching heating chamber 12.
  • the first roller 20 here is a driving roller and is electrically driven
  • the first roller 20 may be referred to as a driving drum in some cases and, in this instance, the second roller 22 as a driven roller can be referred to as a driven drum, for example.
  • the quenching heating chamber 12 is provided with a heater 24 as heating means, namely, a heating device.
  • a plurality of heaters 24 are provided.
  • the heaters 24 each extend in a direction orthogonal to a conveying direction of the workpieces W, namely, in a widthwise direction. While the heaters 24 are provided on an upper side and a lower side in the quenching heating chamber 12 in FIG. 1 , they may be provided also at left and right side portions in the widthwise direction in the quenching heating chamber 12.
  • the workpieces W conveyed by the mesh belt conveyor 16 pass through a heating space (heating region or heating area) HS between the heaters 24.
  • the heaters 24 are not limited to being provided on the upper side and the lower side in the quenching heating chamber 12 and may naturally be provided in any of various layouts or arrangements, for example, only on one of the upper side and the lower side.
  • the heaters 24 may each be an electric heating type heating device or a combustion heating type heating device.
  • Examples of the combustion heating type heating device include a radiant tube burner.
  • the radiant tube burner is a burner of a system in which a fuel is burned in a radiant tube and heating is conducted by radiant heat thereof.
  • a gas supply section 26 configured to supply an atmospheric gas to the quenching heating chamber 12 is provided.
  • the atmospheric gas a nitrogen gas which is a neutral gas is used.
  • the atmospheric gas is not limited to the neutral gas and may be an inert gas such as an Ar gas.
  • the gas supply section 26 includes a supply pipe 30 having an introduction port 28 opened into the quenching heating chamber 12, and a valve 32 provided in the supply pipe 30.
  • the supply pipe 30 is connected to a nitrogen gas tank 33.
  • the gas tank is not limited to the nitrogen gas tank 33 and may be a gas tank according to the gas used as the atmospheric gas, namely, a neutral gas or an inert gas.
  • a partition wall namely, a muffle 34 is provided such that a conveying space in which the workpieces W are conveyed by the mesh belt conveyor 16, namely, the aforementioned heating space HS is isolated from the heaters 24.
  • the muffle 34 is made of a graphite-based material, particularly, made of graphite here.
  • a sheet-shaped or plate-shaped graphite, or a graphite plate, as the muffle 34 can be fabricated by the cold isostatic pressure molding method (CIP).
  • the workpieces W are conveyed so as to pass through a tunnel surrounded by the graphite muffle 34, in a nitrogen gas atmosphere heated by radiant heat of the graphite muffle 34.
  • the muffle 34 as an internal structure in the quenching heating chamber 12 be wholly formed from a graphite-based material
  • at least a part of the muffle 34 may be formed from a graphite-based material.
  • the tunnel defining the heating space HS here is configured by the graphite muffle 34 over the whole periphery thereof, only a part of the tunnel may be configured by the muffle 34.
  • a part or the whole part of the muffle 34 as an internal structure in the quenching heating chamber 12 may be fabricated from other graphite-based material, specifically, C/C composite which is a graphite-based material. Further, at least a part of the internal structures in the quenching heating chamber 12 other than the muffle may be fabricated from a graphite-based material.
  • An outside air block structure 36 is applied to a conveying-in end (at the left end of FIG. 1 ) of the mesh belt conveyor 16.
  • the outside air block structure 36 has an inlet constriction section 36a at a part entering the furnace of the mesh belt 18, and an outlet constriction section 36b at a part going out of the furnace of the mesh belt 18.
  • the inlet constriction section 36a and the outlet constriction section 36b are set close to each other, to thereby form substantially one entrance of the mesh belt 18.
  • suction of outside air into the furnace due a pressure difference generated when the entrance of the mesh belt 18 is divided can be prevented, and stabilization of the in-furnace atmosphere can be realized.
  • a plurality of curtain bodies 36c are provided at the conveying-in end of the mesh belt conveyor 16.
  • the curtain bodies 36c have flexibility and are sheet-shaped here, but may have other shape, for example, may be line-shaped or string-shaped.
  • the plurality of curtain bodies 36c are suspended so as to droop down from the upper side toward the lower side in the vertical direction.
  • the curtain bodies 36c here are formed of a nickel-based sheet material.
  • the curtain bodies 36c may be produced from other material, for example, a carbon-based material, a glass-based material, a ceramic-based material, or a metallic material having sufficient strength and flexibility at a heat treatment temperature such as a steel material or a titanium-based material.
  • the quenching oil tank 14 on the downstream side of the quenching heating chamber 12 is provided at a conveying-out end (namely, an end portion on the second roller 22 side in FIG. 1 ) of the mesh belt conveyor 16.
  • a chute 13 extending in the vertical direction is provided at a conveying-out end (on the right side in FIG. 1 ) of the quenching heating chamber 12.
  • the chute 13 is located below a dropping space, described later, in the heating space HS.
  • the chute 13 extends to the inside of the quenching oil tank 14. While the chute 13 does not reach an oil surface S in the quenching oil tank 14, it may extend into the oil in the quenching oil tank 14.
  • the quenching oil tank 14 communicates with the inside of the quenching heating chamber 12 through the chute 13.
  • the atmospheric gas substantially the same as inside the quenching heating chamber 12 can be present to the oil surface S in the quenching oil tank 14.
  • the gas in contact with the oil surface S is different from a converted gas and is a nitrogen gas which is a neutral gas not containing hydrogen and carbon monoxide, the possibility of reactions such as oxidation of the quenching oil can be suppressed to extremely low.
  • a neutral gas or an inert gas for example, a nitrogen gas
  • a further supply pipe be connected to the nitrogen gas tank 33 and the nitrogen gas be supplied between the oil curtain C and the oil surface S through the supply pipe.
  • the heat treatment furnace 10 further includes oil flow-in preventing means OP configured to prevent flowing-in of an oil (for example, oil smoke) from the quenching oil tank 14 into the quenching heating chamber 12.
  • the oil flow-in preventing means OP also called an oil flow-in preventing device here includes a fluid curtain forming section 40.
  • the fluid curtain forming section 40 configured to form a fluid curtain between the quenching heating chamber 12 and the quenching oil tank 14 is provided as the oil flow-in preventing means OP.
  • the fluid curtain forming section 40 is provided in the chute 13. While the fluid curtain forming section 40 here is configured so as to form an oil curtain, it may be configured, for example, so as to form an air curtain by a nitrogen gas.
  • a supply port 46 to be described later can be a gas supply port, which can be connected to a tank of nitrogen gas or the like.
  • the fluid curtain forming section 40 includes an oil curtain forming device 42 configured to form the oil curtain C between the quenching heating chamber 12 and the quenching oil tank 14.
  • An oil passage 43 for scooping out the oil from the tank 14 is provided.
  • the oil passage 43 is provided with an oil pump 44.
  • the oil passage 43 has the oil supply port 46 provided at the position of the chute 13.
  • the oil curtain forming device 42 includes a rectifying member 48 so as to form the oil curtain C by adjusting the flow of the oil coming out of the oil supply port 46.
  • the rectifying member 48 is provided to extend between an oil delivery port 49 provided in the chute 13 and the oil supply port 46.
  • the rectifying member 48 includes a smoothly recessed and curved surface 48a. The oil flowing out from the oil supply port 46 can flow along the recessed and curved surface 48a, so that the oil curtain C as depicted in FIG. 1 is formed.
  • the fluid curtain forming section 40 includes an oil accepting section 50 provided between the quenching heating chamber 12 and the quenching oil tank 14 so as to accept the oil curtain C.
  • the oil accepting section 50 is provided at a position facing the rectifying member 48 of the oil curtain forming device 42 so as to accept the oil curtain generated by the oil curtain forming device 42. More specifically, the oil accepting section 50 is provided to open to the chute 13.
  • the oil accepting section 50 is provided at a predetermined position so as to accept the oil curtain C while preventing the oil curtain C from directly colliding on the oil surface S in the quenching oil tank 14.
  • the oil accepting section 50 is connected to the quenching oil tank 14 on the lower side thereof.
  • the oil accepting section 50 includes a foam restraining section 52.
  • the foam restraining section 52 is provided so as to restrain foam of the oil generated attendant on the acceptance of the oil curtain C, preferably to cause the foam to disappear.
  • the foam restraining section 52 is configured as a member having an oil passage of a labyrinth structure, but may be any of various devices and structures producing such a foam-restraining effect.
  • the quenching oil tank 14 is provided with a conveyor 54 for conveying the workpieces W from the quenching oil tank 14 toward the tempering heating chamber.
  • the heat treatment furnace 10 configured as above includes a controller 60.
  • the controller 60 is what is generally called a computer including a processing section (for example, CPU), a storage section (for example, ROM, RAM), an input-output port, and the like.
  • a temperature sensor 62 for detecting the temperature of an atmospheric gas in the quenching heating chamber 12, a first gas sensor 64 and a second gas sensor 65 for detecting gas components (concentrations) of the atmospheric gas in the quenching heating chamber 12 are connected to the controller 60.
  • the first gas sensor 64 here is an oxygen sensor
  • the second gas sensor 65 is a CO sensor;
  • the heat treatment furnace 10 can include one or a plurality of gas sensors selected from an oxygen sensor, a CO sensor, and/or a CO 2 sensor, for example.
  • the controller 60 controls rotation of a driving motor for the first roller 20, operation of the heaters 24, an opening degree (for example, opening and closing) of the valve 32, operation of the oil pump 44, and the like according to a predetermined program so as to keep in a preferable state the atmospheric gas in the quenching heating chamber 12, particularly, the heating space HS, and to enable preferable performance of heat treatment of the workpieces 12.
  • the controller 60 has a control section for the driving motor for the first roller 20, a control section for the heaters 24, a control section for the valve 32 of the gas supply section 26, and a control section for the oil pump 44, as functional modules, namely, functional sections. Each functional module is realized by executing a program stored in the storage section by the processing section of the controller 60.
  • these functional modules are not limited to being realized by one controller 60 and may be realized individually by a plurality of controllers, for example. It is to be noted that the controller 60 is connected to a display device 68, where results of processing by the controller 60, various values of the atmospheric gas in the quenching heating chamber 12, and the like are displayed. The description of an input device, or input means such as a keyboard, for input to the controller 60 is omitted.
  • the controller 60 stores therein a program and data for executing bright heat treatment of the workpieces W, during quenching heating.
  • the workpieces W can each be of any of various materials, and here, it is made of a steel material.
  • FIG. 2 depicts conceptually a part of an Ellingham diagram E.
  • the Ellingham diagram is a graph in which the axis of abscissas represents temperature, the axis of ordinates represents Gibbs energy of formation, and, with respect to various oxides, standard Gibbs energy of formation ( ⁇ G 0 ) at each temperature is plotted.
  • ⁇ G 0 standard Gibbs energy of formation
  • the region GA is a reduction region for iron and also a reduction region for carbon, a problem of oxidation or decarburization of the workpieces W during quenching heating does not occur.
  • a program or the like be specified such that the ⁇ G 0 of the atmospheric gas is located in a further specific region (second predetermined region) within the region GA (first predetermined region).
  • the line L1 or a line designated further additionally can be made to be a straight line for the oxide according to the component. Therefore, the controller 60 stores data on various oxides, and a user can designate one or a plurality of oxides by the input means.
  • the ⁇ G 0 can be calculated based on an oxygen partial pressure and an absolute temperature by using formula (1).
  • P(O 2 ) is the oxygen partial pressure
  • T is the absolute temperature
  • R is a gas constant.
  • ⁇ G 0 RTlnP O 2
  • ⁇ G 0 can be calculated based on a CO partial pressure and an absolute temperature by using formula (3).
  • P(CO) is the CO partial pressure
  • T is the absolute temperature
  • R is a gas constant.
  • the ⁇ G 0 can be calculated based on the oxygen partial pressure by using formula (1). Besides, the ⁇ G 0 can be determined based on the carbon monoxide partial pressure (CO partial pressure) by using formula (3) .
  • FIG. 3 depicts an example of display on the display device 68 connected to the controller 60.
  • the display device 68 displays a plot P of the ⁇ G 0 of the atmospheric gas generated by the ⁇ G 0 calculation section of the controller 60 on the displayed Ellingham diagram E.
  • the line L1 and the line L2 are the same as those in FIG. 2 .
  • the atmospheric gas of the nitrogen gas contains a trace amount of oxygen.
  • the oxygen reacts with graphite constituting the muffle 34 and the mesh belt 18 to be carbon monoxide (CO), which is discharged through gaps between members of the heat treatment furnace 10 or the like to outside of the heat treatment furnace 10, together with the atmospheric gas serving also as a carrier gas. Therefore, the nitrogen gas atmosphere comes to have a further lowered oxygen concentration, so that oxidation, decarburization, and the like of the workpieces occur with more difficulty.
  • CO carbon monoxide
  • the oil curtain C is accepted by the oil accepting section 50, foam of the oil can be prevented from being generated at the oil surface S by the oil curtain C. Further, by the foam restraining section 52 of the oil accepting section 50, foam of the oil generated in the oil accepting section 50 attendant on the acceptance of the oil curtain C can also be restrained, preferably caused to disappear. Therefore, the oil used for the oil curtain C can return to the oil tank 14 substantially without generating foam. Accordingly, generation of oil smoke and the like can be prevented more suitably.
  • the workpiece W thus quenched is conveyed by the conveyor 54 from the quenching oil tank 14 toward the tempering heating chamber.
  • a nitrogen gas is supplied particularly as the in-furnace atmospheric gas, and the in-furnace structures, or the internal structures, such as the muffle 34 in the quenching heating chamber 12 are made of a graphite material. Therefore, as has been described above, quenching heating can be performed in the nitrogen atmospheric gas with a lower oxygen concentration, so that appearance of a modified layer due to oxidation, decarburization, or the like at the surface of the workpiece W during quenching heating can be prevented sufficiently.
  • the oil flow-in preventing means OP such as the fluid curtain forming section 40 is provided.
  • flowing-in of the oil into the quenching heating chamber 12 can be suitably prevented, so that the quenching heating can be performed further suitably.
  • fluid curtain forming section 40 is provided as the oil flow-in preventing means OP in the above heat treatment furnace 10
  • various configurations for preventing flowing-in of the oil into the quenching heating chamber 12 may be provided in addition to the fluid curtain forming section or in place of the fluid curtain forming section 40.
  • a pump for sucking oil smoke and the like may be provided at the chute 13.
  • a heat treatment furnace 10A of a second embodiment described later includes such a configuration.
  • the steel material as the workpiece W to be subjected to quenching treatment includes those containing at least one component of carbon (C), chromium (Cr), manganese (Mn), silicon (Si), and the like in a predetermined ratio.
  • C carbon
  • Cr chromium
  • Mn manganese
  • Si silicon
  • the alloy steels for machine structure are obtained by adding such an element as chromium or manganese to the carbon steels for machine structure, and examples thereof include manganese chromium steel (SMnC), chromium steel (SCr), and chromium molybdenum steel (SCM).
  • an internal oxidation phenomenon such as intergranular oxidation in which crystal grain boundaries at a surface layer are oxidized by oxygen in the atmospheric gas may occur in conventional quenching heating using a converted gas.
  • a chromium oxide, a manganese oxide, and the like may be generated.
  • Such internal oxidation may cause abnormal breakage or the like, and therefore, machining such as grinding the surface layer is generally conducted after the heat treatment.
  • FIG. 4 depicts conceptually a part of the Ellingham diagram E.
  • the line L1 approximately straight line of standard Gibbs energy of formation of iron (Fe) and iron oxide (FeO)
  • a straight line L3 which is an approximate straight line of standard Gibbs energy of formation of chromium (Cr) and chromium oxide (Cr 2 O 3 ) is also depicted.
  • the plot P of the ⁇ G 0 of the atmospheric gas is required to be located in a narrow region GA1 on the lower side of line L1 and line L2 in the graph of FIG. 4 , taking the aforementioned oxidation, decarburization, cementation, and the like into account.
  • the region GA1 is a region on the upper side relative to the line L3, and by locating the plot P of the ⁇ G 0 of the atmospheric gas in the region GA1, oxidation of Cr occurs.
  • the nitrogen gas is used as the atmospheric gas and the internal structures in the quenching heating chamber are made of a graphite material
  • the plot P of the ⁇ G 0 of the atmospheric gas can be easily and securely located in a region GA2 on the lower side of the lines L1, L2, and L3, even taking the oxidation, decarburization, cementation, and the like at the surface of the workpiece into account. Therefore, for example, when the workpiece is chromium steel, oxidation, decarburization, and the like of the workpiece can be suitably prevented, while suitably preventing internal oxidation such as intergranular oxidation of Cr or the like.
  • the heat treatment furnace 10 of the present embodiment is extremely excellent in terms of atmospheric gas control.
  • the region GA2 is an example of the second predetermined region.
  • a drop arch may be provided in place of or in addition to the partition curtains.
  • the drop arch be made of a graphite-based material such as a C/C composite.
  • the atmospheric gas can be made to be a low-oxygen atmosphere more suitably.
  • the drop arch may be configured integral with the muffle 34, or may be configured as a body separate from the muffle 34 and disposed separate from or in contact with the muffle 34.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Combustion & Propulsion (AREA)
  • Tunnel Furnaces (AREA)
  • Furnace Details (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
EP20859246.9A 2019-08-27 2020-08-22 Wärmebehandlungsofen Pending EP4023985A4 (de)

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JPH0339887A (ja) * 1989-07-05 1991-02-20 Kanto Yakin Kogyo Kk 雰囲気熱処理方法とその装置
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JPH09101086A (ja) * 1995-10-02 1997-04-15 Kanto Yakin Kogyo Kk 高温雰囲気炉
ATE207546T1 (de) * 1996-08-30 2001-11-15 Franz Hillingrathner Rundtaktofen zum behandeln von werkstücken
JP4458079B2 (ja) * 2006-09-27 2010-04-28 株式会社Ｉｈｉ 真空浸炭処理装置
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