EP2796570A1 - Procédé de régulation d'une température de point de rosée d'un four de traitement thermique - Google Patents

Procédé de régulation d'une température de point de rosée d'un four de traitement thermique Download PDF

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Publication number
EP2796570A1
EP2796570A1 EP13002194.2A EP13002194A EP2796570A1 EP 2796570 A1 EP2796570 A1 EP 2796570A1 EP 13002194 A EP13002194 A EP 13002194A EP 2796570 A1 EP2796570 A1 EP 2796570A1
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EP
European Patent Office
Prior art keywords
heat treatment
treatment furnace
dew point
point temperature
nitrogen
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.)
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Application number
EP13002194.2A
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German (de)
English (en)
Inventor
Matthias Bors
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.)
Linde GmbH
Original Assignee
Linde GmbH
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Filing date
Publication date
Application filed by Linde GmbH filed Critical Linde GmbH
Priority to EP13002194.2A priority Critical patent/EP2796570A1/fr
Priority to PCT/EP2014/000892 priority patent/WO2014173494A1/fr
Publication of EP2796570A1 publication Critical patent/EP2796570A1/fr
Withdrawn legal-status Critical Current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
    • C21D1/74—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
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C21D11/00—Process control or regulation for heat treatments

Definitions

  • the invention relates to a method for controlling a dew point temperature of a heat treatment furnace for a heat treatment of workpieces and a heat treatment furnace for a heat treatment of workpieces.
  • certain material properties can be generated by exposing the workpieces to certain temperatures or temperature gradients.
  • Methods of heat treatment for example, the annealing, curing or tempering, with which the structure of a metal, so the arrangement of the crystallites contained, can be selectively influenced. Properties such as hardness, toughness, cold workability or microstructure homogeneity of the workpieces can be planned in this way.
  • the components of UHS steel can be austenitized in heat treatment plants and then formed in a press and simultaneously cooled and hardened. Components with a strength ⁇ 1450MPa can be manufactured in this way.
  • the object which now arises to those skilled in the art is to provide a way to prevent the formation of hydrogen in heat treatment furnaces and associated damage to workpieces manufactured in the heat treatment furnaces.
  • This object is achieved by an inventive method for controlling a dew point temperature of a heat treatment furnace for a heat treatment of workpieces and by a heat treatment furnace according to the invention for a heat treatment of workpieces according to the independent claims.
  • nitrogen and air are supplied to the heat treatment furnace, thereby producing a nitrogen-air atmosphere in the heat treatment furnace.
  • the amount of nitrogen supplied is determined based on an actual value of the dew point temperature determined in the heat treatment furnace.
  • the actual value of the dew point temperature is controlled by this specific amount of nitrogen supplied to a desired value.
  • the target value of the dew point temperature is expediently chosen such that no or hardly formation of hydrogen can occur.
  • the invention is suitable for all types of heat treatment furnaces or heat treatment systems.
  • the heat treatment furnace can be designed as a rotary drum furnace, a roller hearth furnace or a chamber furnace.
  • the invention is based on the finding that an atmosphere of a heat treatment furnace made of nitrogen and air has particular advantages.
  • said atmospheric composition has significant advantages over a pure nitrogen atmosphere.
  • a pure nitrogen atmosphere in a heat treatment furnace can prevent formation of hydrogen and thus the uptake of hydrogen into the workpieces and damage to the workpieces
  • a nitrogen atmosphere favors the formation of a fine silicon nitride layer on the fabricated workpieces, which in turn leads to increased wear of tools used to machine the finished workpieces (for example, in the forming of heat-treated sheets).
  • the use according to the invention of a nitrogen-air atmosphere for regulating the dew point temperature of the heat treatment furnace prevents or at least reduces the formation of hydrogen in the heat treatment furnace and thus damage to finished workpieces.
  • the reduced nitrogen content in the atmosphere of the heat treatment furnace compared to the pure nitrogen atmosphere reduces the reaction of the nitrogen with the workpieces, thereby preventing, or at least preventing, the formation of a silicon nitride layer on the workpieces and thus the associated increased wear of tools for machining the workpieces is reduced.
  • the inventive supply of the specific amount of nitrogen, the ratio of the nitrogen-air atmosphere is changed in dependence on the actual value of the dew point temperature.
  • the dew point temperature in the heat treatment furnace can accordingly be adjusted flexibly and reliably.
  • the invention is furthermore particularly suitable as a measure for a so-called Flue Gas Management System for reducing exhaust-induced water fractions in heat treatment furnaces.
  • dried air is supplied to the heat treatment furnace.
  • only the dried air or a mixture of (ambient) air and dried air can be supplied to the heat treatment furnace. Due to the reduced proportion of water in dried air, the formation of hydrogen from the air in the heat treatment furnace can be further prevented.
  • the heat treatment furnace preferably has at least one chamber or zone.
  • chambers can be physically separated units of the heat treatment furnace.
  • zones may also be formed as different regions within a chamber which have no fixed boundary to each other.
  • different temperatures prevail in the different chambers or zones and, in particular, different process steps of the heat treatment of the workpieces take place. Accordingly, different dewpoint temperatures can prevail in the different chambers or zones.
  • the regulation according to the invention of the dew point temperature is carried out for the at least one chamber or zone.
  • the inventive control of Dew point temperature can be performed over the entire heat treatment furnace as a zone or the heat treatment furnace can be divided into several zones, for each of which the control of the dew-point temperature according to the invention is carried out separately.
  • the regulation according to the invention of the dew-point temperature for each chamber or zone is carried out individually and independently of one another.
  • the dew point temperature of each chamber or zone can be suitably regulated to a separate, individual desired value.
  • the amount of nitrogen introduced is determined on the basis of the actual value of the dew-point temperature detected in the respective chamber or zone and on the basis of the individual setpoint value of the dew-point temperature determined for the respective chamber or zone.
  • an amount of supplied air is determined based on the actual value of the dew point temperature determined in the heat treatment furnace such that the actual value of the dew point temperature is adjusted to the target value by the determined amount of supplied nitrogen and supplied air.
  • Value is regulated.
  • the dew point temperature can thus be regulated even more flexible.
  • the ratio of the nitrogen-air mixture in the heat treatment furnace can thus also be set more flexibly and, if appropriate, adapted to different workpiece materials.
  • An upper limit of the dew-point temperature is preferably determined by the amount of supplied air.
  • a lower limit of the dew-point temperature is preferably determined by the amount of nitrogen supplied. The set target value is then within the range of lower and upper limit.
  • the dew point temperature to target values between -5 ° C and -60 ° C, in particular between -10 ° C and -40 ° C, regulated.
  • the dew point temperature can be controlled by means of the method according to the invention on the one hand to target values less than a minimum possible dew point temperature for a pure air atmosphere of about -10 ° C.
  • the dew point temperature can be controlled to target values greater than a dew point temperature for a pure nitrogen atmosphere of about -60 ° C.
  • the amount of nitrogen is fed to the heat treatment furnace at high speed.
  • a homogeneous nitrogen-air atmosphere can be generated in the heat treatment furnace.
  • the detection of the actual value of the dew point temperature and thus the analysis of the dew point temperature can thus be carried out more reliably and precisely.
  • the dew point temperature in particular, as well as the temperature of the heat treatment furnace can generally be adjusted homogeneously and without significant local variations.
  • a Carbojet process is used to supply the amount of nitrogen.
  • the Carbojet method and associated Carbojet nozzles or Carbojet lances are distributed by the applicant.
  • injection of small amounts of nitrogen at high speeds of up to 250-300 m / s is possible in individual areas of the heat treatment furnace.
  • the accuracy of analyzers as well as homogeneous gas and temperature distribution can be further improved.
  • a Carbojet process see for example the publication DE 10 2008 009 818 A1 directed.
  • the heat treatment furnace is operated by means of at least one premixing fuel gas-oxygen burner, in particular at least one hydrogen-oxygen burner.
  • Premixing fuel gas oxygen burners are characterized by a particularly high heat transfer efficiency.
  • a burner head of the premixing fuel gas oxygen burner while a gas mixture of fuel gas and oxygen is already supplied and not only generated in the corresponding burner head.
  • Premixing burners produce particularly hard flames, which are suitable for melting larger surface areas, which may also have pits or other irregularities.
  • Corresponding burners are also known as so-called Hydropox burners and are sold under this brand name by the applicant. For a detailed description of the Hydropox burner, see, for example, the data sheet "HYDROPOX®. Optimal glass surface treatment with pre-mixing hydrogen / oxygen burners.” referred to the applicant.
  • premixing fuel gas oxygen burner for the heat treatment furnace significantly affects the dew point temperature in the heat treatment furnace.
  • the dew point temperature of a heat treatment furnace with premixing fuel gas-oxygen burner can be controlled simply and reliably.
  • the invention is not limited to the use of premixing fuel gas-oxygen burners, but is also suitable for the use of, for example, external mixing burners.
  • an oxyfuel burner is possible.
  • an oxy-fuel burner does not use air, but rather an oxygen-rich gas, in particular (virtually) pure oxygen as oxidizer.
  • the workpieces are rapidly heated in the heat treatment furnace for the heat treatment.
  • This procedure is known as "Rapid Heating”. Since workpieces for a "rapid heating” process are heated to very high temperatures in a short time, premixing fuel gas oxygen burners, in particular hydropox burners, are suitable for a "rapid heating” process.
  • the rapid heating significantly affects the dew point temperature within the heat treatment furnace. Therefore, the invention is particularly suitable for a "rapid heating” process.
  • locally different material properties are preferably produced by local heat treatment.
  • This procedure is generally known as "tailored properties".
  • certain areas of a workpiece may be press-hardened, and other areas may be formed such that they have ductility and thus can absorb more energy by plastic deformation.
  • Possibilities for the production of "tailored properties”, ie of such locally different properties, can be, for example, a targeted influencing of alloy components of corresponding semi-finished products, a production of so-called “tailored welded blanks", ie blanks which are made of different materials, partial (local) Heating by means of inductive or Conductive heating technologies, a partial temperature control of certain areas of the press hardening tools by local heating, a partial tempering press-hardened components and / or masking of certain component areas to suppress heating (and thus austenitization).
  • the dew point temperatures of the individual zones can be regulated in a particularly simple manner independently of each other.
  • the heat treatment furnace is used for a region-wise austenitization.
  • This procedure is commonly known as tailored austenitizing.
  • different zones of the heat treatment furnace can also have different temperatures and different dew point temperatures in the case of a "tailored austenitizing" process. Therefore, the method according to the invention is also particularly suitable for controlling the dew point temperatures in the course of a tailored austenitizing process.
  • the invention further relates to a heat treatment furnace for a heat treatment of workpieces.
  • a heat treatment furnace for a heat treatment of workpieces.
  • Embodiments of the heat treatment furnace according to the invention will become apparent from the above description of the method according to the invention in an analogous manner and from the underlying embodiment, the features shown there can also be used alone or in other combinations.
  • FIG. 1 A preferred embodiment of a heat treatment furnace according to the invention for a heat treatment of workpieces is in FIG. 1 shown schematically and designated 100.
  • the heat treatment furnace is formed as a roller hearth furnace 100 in this example.
  • roller hearth furnace 100 On a plurality of rollers 103, workpieces 102 are conveyed through the roller hearth furnace 100 (in FIG FIG. 1 from left to right).
  • the roller hearth furnace 100 has two zones (1 01 a and 101 b), which are delimited from one another by heat treatment technology. In the two zones 101 a and 101 b, two different process steps of the heat treatment of the workpieces 102 take place.
  • the zone 101 a has a premixing fuel gas-oxygen burner 105 (shown only schematically).
  • the premixing fuel gas-oxygen burner 105 is formed in this example as a premixing hydrogen-oxygen burner, in particular as a Hydropox burner.
  • the Hydropox burner 105 produces a comparatively high temperature in the zone 101 a.
  • workpieces 102 are first heated to a high temperature in a short time, in particular according to a "rapid heating" process. Subsequently, the workpieces 102 pass through the holding zone 101 b and are homogenized therein.
  • the roller hearth furnace 100 is adapted to an embodiment of an inventive To carry out the process, which in FIG. 2 is shown schematically as a block diagram. In the course of this, the dew point temperature in each of the zones 101 a and 101 b is regulated separately from one another.
  • each of the zones 101a and 101b respectively has measuring instruments 110a and 110b, which are connected to a computing unit 120, in particular a control unit, for example a control cabinet, indicated by reference numeral 110
  • Method step 201 is in each case an actual value of the dew point temperature of the zones 101 a and 101 b determined by means of the measuring instruments 110 a and 110 b.
  • an amount of dried air and an amount of nitrogen are determined in the control unit 120 in step 202.
  • a nitrogen-air mixture is determined, which forms the atmosphere of the respective zone 101 a and 101 b of the roller hearth furnace 100.
  • the dew point temperature of the respective zone is changed.
  • the amount of dried air and the amount of nitrogen are determined such that the actual value of the dew point temperature of the respective zones 101 a and 101 b is regulated to a predetermined desired value.
  • the desired values for the two zones 101 a and 101 b may be the same or different.
  • the controller 120 communicates with a gas control unit 130, indicated by reference numeral 125.
  • the gas control unit supplies the determined amount of nitrogen and dried air to the zones 101 a and 101 b.
  • the roller hearth furnace 100 has a container for dried air 140 and a container for nitrogen 150, which are each connected via lines 141 and 151 to the gas control unit 130.
  • the line 151 includes an evaporator 160.
  • the gas control unit 130 is connected via lines 130a and 130b to the zones 101 a and 101 b and leads the zones 101 a and 101 b in step 203, the amount of dried air and nitrogen to.
  • the amounts of dried air and nitrogen can be supplied in each case via separate lines to the zones 101 a and 101 b or via one or more common lines per zone. If the amounts of nitrogen and dried air to the zones 101 a and 101 b supplied via separate lines, the amounts of nitrogen can be supplied to the chambers 101 a and 101 b in particular via a high-speed Carbojet method.
  • the process begins again at step 201 with the determination of the actual values of the dew point temperatures of the zones 101 a and 101 b of the roller hearth furnace 100.
  • the dew point temperatures are thus continuously monitored and controlled in real time to the predetermined target values.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Tunnel Furnaces (AREA)
EP13002194.2A 2013-04-25 2013-04-25 Procédé de régulation d'une température de point de rosée d'un four de traitement thermique Withdrawn EP2796570A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP13002194.2A EP2796570A1 (fr) 2013-04-25 2013-04-25 Procédé de régulation d'une température de point de rosée d'un four de traitement thermique
PCT/EP2014/000892 WO2014173494A1 (fr) 2013-04-25 2014-04-03 Procédé de réglage du point de rosée d'un four de traitement thermique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP13002194.2A EP2796570A1 (fr) 2013-04-25 2013-04-25 Procédé de régulation d'une température de point de rosée d'un four de traitement thermique

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EP2796570A1 true EP2796570A1 (fr) 2014-10-29

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT202000013285A1 (it) * 2020-06-04 2021-12-04 Danieli Off Mecc Procedimento e apparato per il riscaldo di prodotti siderurgici
DE102022118249A1 (de) 2022-07-21 2024-02-01 Thyssenkrupp Steel Europe Ag Verfahren zur Einstellung einer Ofenatmosphäre in einem Wärmebehandlungsofen

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11149327B2 (en) 2019-05-24 2021-10-19 voestalpine Automotive Components Cartersville Inc. Method and device for heating a steel blank for hardening purposes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008009818A1 (de) 2008-02-19 2009-08-20 Linde Ag Verfahren und Vorrichtung zur Wärmebehandlung von Werkstoffen
EP2570503A2 (fr) * 2011-09-15 2013-03-20 Benteler Automobiltechnik GmbH Procédé et dispositif de chauffage d'une platine préenduite en acier

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008009818A1 (de) 2008-02-19 2009-08-20 Linde Ag Verfahren und Vorrichtung zur Wärmebehandlung von Werkstoffen
EP2570503A2 (fr) * 2011-09-15 2013-03-20 Benteler Automobiltechnik GmbH Procédé et dispositif de chauffage d'une platine préenduite en acier

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT202000013285A1 (it) * 2020-06-04 2021-12-04 Danieli Off Mecc Procedimento e apparato per il riscaldo di prodotti siderurgici
WO2021245716A1 (fr) * 2020-06-04 2021-12-09 Danieli & C. Officine Meccaniche S.P.A. Appareil de chauffage de produits en acier
DE102022118249A1 (de) 2022-07-21 2024-02-01 Thyssenkrupp Steel Europe Ag Verfahren zur Einstellung einer Ofenatmosphäre in einem Wärmebehandlungsofen

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