EP0156147B1 - Procédé et dispositif pour le recuit de pièces métalliques - Google Patents

Procédé et dispositif pour le recuit de pièces métalliques Download PDF

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Publication number
EP0156147B1
EP0156147B1 EP85101547A EP85101547A EP0156147B1 EP 0156147 B1 EP0156147 B1 EP 0156147B1 EP 85101547 A EP85101547 A EP 85101547A EP 85101547 A EP85101547 A EP 85101547A EP 0156147 B1 EP0156147 B1 EP 0156147B1
Authority
EP
European Patent Office
Prior art keywords
furnace
opacity
protective gas
volume flow
annealing
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.)
Expired
Application number
EP85101547A
Other languages
German (de)
English (en)
Other versions
EP0156147A1 (fr
Inventor
Reinhard Dipl.-Ing. Strigl
Hubert Dipl.-Ing. Majerus
Thomas Dipl.-Ing. Mahlo
Alexander Jurmann
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 Gas AG
Original Assignee
Linde GmbH
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Filing date
Publication date
Application filed by Linde GmbH filed Critical Linde GmbH
Priority to AT85101547T priority Critical patent/ATE28480T1/de
Publication of EP0156147A1 publication Critical patent/EP0156147A1/fr
Application granted granted Critical
Publication of EP0156147B1 publication Critical patent/EP0156147B1/fr
Expired 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • C21D9/52—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
    • C21D9/667—Multi-station furnaces
    • C21D9/67—Multi-station furnaces adapted for treating the charge in vacuum or special atmosphere

Definitions

  • the invention relates to a method and a device for annealing metal parts under protective gas in a furnace, into which the protective gas is temporarily introduced at a maximum volume flow.
  • shielding gas supply for the annealing of metal parts, which differ among other things by the start and duration of the shielding gas supply and by the shielding gas quantity and shielding gas type.
  • the purpose of pre-rinsing before the start of glow is to displace the oxygen and to avoid the risk of explosion.
  • the maximum amount of protective gas is also flushed. This process step is common to all annealing processes.
  • the maximum amount of protective gas is also flushed.
  • the protective gas outlet is closed. During the entire cooling process, i.e. until the end of the annealing process, only the amount of shielding gas that is required to cover the leakage losses is fed to the furnace.
  • Shielding gas consumption causes costs that are a significant part of the annealing costs. To reduce the annealing costs, the lowest possible shielding gas consumption is therefore sought. However, economical shielding gas consumption must not cause smoldering edges or lower tape cleanliness.
  • the invention is therefore based on the object of specifying a method of the type described at the outset in which the protective gas consumption is lower than conventional methods without impairing the quality of the annealed metal parts.
  • This object is achieved in that the protective gas is supplied to the furnace during the heating phase only at a maximum volume flow within a period in which the opacity of the furnace atmosphere is greater than that of the furnace atmosphere at ambient temperature.
  • the method according to the invention is based on the knowledge that the furnace does not have to be constantly flushed with the maximum protective gas volume flow during the heating phase. Rather, the furnace can be supplied with a significantly lower volume flow than the maximum protective gas volume flow at certain time intervals during the heating phase, without the quality of the annealed metal parts suffering.
  • the periods in which protective gas with a maximum volume flow or with a low volume flow is to be supplied to the oven are determined by the value of the opacity of the furnace atmosphere.
  • the opacity of the furnace atmosphere is to be understood here as the light absorption capacity of this atmosphere.
  • the opacity depends on the foreign dirt that is present in the furnace atmosphere, on the carbon content in the furnace and on the emulsion evaporation rate. It was found that the opacity - starting from a value of the ogacity of the furnace atmosphere at ambient temperature, the ambient value - changes only slightly immediately after the start of the heating phase. After a certain time of, for example, about 2 hours, the opacity of the furnace atmosphere increases sharply, however, after reaching a maximum, it drops back to the ambient value. This value is reached, for example, within 13 to 18 hours (depending on the furnace and batch size).
  • protective gas with a maximum volume flow is supplied to the furnace in the heating phase only when the opacity exceeds the setpoint value.
  • a smaller volume flow than the maximum volume flow is sufficient for flushing an annealing furnace.
  • the smaller volume flow lies in a range between the amount of shielding gas covering the leak rate of the respective furnace and about 2 to 5 times the amount of leak rate.
  • the volume flow of the protective gas is consequently adapted to the time course of the opacity of the furnace atmosphere.
  • at least one volume flow covering the leak rate is fed to the furnace.
  • flushing takes place with a higher volume flow up to the maximum protective gas volume flow.
  • a blanket gas saving of up to 70% could be achieved in the heating and baking and recrystallization annealing of cold-rolled steel sheet.
  • conventional methods can be achieved.
  • increased tape cleanliness was found.
  • the method according to the invention thus makes it possible to reduce annealing costs. It also improves the quality of the products made using the proposed process.
  • the saving of protective gas that can be achieved with the method according to the invention presumably has the following causes: In the first hours (1.5 to 2.5 hours) after the start of annealing, the emulsion evaporation rate is very low because the temperature in the furnace is low. During this time, an amount of shielding gas per unit of time that is well below the maximum shielding gas rate is sufficient. It was found that the opacity drops back to the ambient value within a certain period of time after the start of annealing. The period of time is independent of the thickness and roughness of the metal parts to be annealed (steel strips) and also regardless of whether the metal parts (e.g. steel strips after rolling) have been stored for a long time or have been brought directly into the furnace. The period with large opacity values ends at the latest 17 hours after the start of glow. From this point on, a lower amount of protective gas per unit of time is sufficient to purge the furnace.
  • the protective gas with maximum volume flow is only fed into the furnace within a period in which the opacity of the furnace atmosphere is greater than the opacity of the protective gas supplied to the furnace by 2% and more, preferably by 5% and more. In practice, this procedure has proven to be completely sufficient.
  • the protective gas consists of nitrogen and small amounts of a reducing additional gas, e.g. B. hydrogen.
  • a flushing gas mixture of this type it is not necessary to flush a furnace before the actual annealing. Rinsing can rather begin with the annealing process, since the oxygen content in the atmosphere quickly drops from 21% by volume to less than 0.5% by volume and the temperature of the retort rises only very slowly and there is therefore no risk of explosion.
  • the protective gas consumption can be reduced again by this measure.
  • the opacity of the furnace atmosphere is measured continuously, the measured value is compared with a target value and protective gas is automatically fed to the furnace with a maximum volume flow, as long as the opacity of the furnace atmosphere is above the target value.
  • the target value which is approximately the same as the ambient value or the value specified in claim 2
  • protective gas with a maximum volume flow is passed immediately. The maximum volume flow is only reduced to a smaller volume flow once the opacity has dropped below the setpoint.
  • the second variant enables an even better adaptation of the required shielding gas supply to the opacity of the furnace atmosphere and thus minimal shielding gas consumption.
  • the opacity of the furnace atmosphere is measured continuously and, on the basis of a comparison of the measurement signal with the setpoint, a control command for increasing or throttling the shielding gas supply is given in order to adjust the measured opacity value to the setpoint.
  • the protective gas volume flow is gradually increased with increasing opacity after the setpoint is exceeded. As soon as the opacity of the furnace atmosphere drops again, the shielding gas supply is also reduced.
  • the shielding gas is fed to the furnace with maximum volume flow depending on the time.
  • the volume flow is clearly determined by a schedule.
  • the schedule is saved in a schedule provider and the entered program is processed after the start.
  • a switch is made to the maximum protective gas volume flow.
  • the system switches back to a smaller volume flow.
  • a device suitable for carrying out the method essentially consists of an annealing furnace into which a supply line and an exhaust gas line open, and is characterized by an opacity probe connected to a control unit and exposed to the atmosphere formed in the furnace, and by a bypass line connected in parallel with the supply line with a valve connected to the control unit.
  • the furnace Via the supply line, the furnace can be supplied with the basic volume flow, which serves to cover the leak rate and supplies the shielding gas quantities that are required to flush the furnace as long as the opacity of the furnace atmosphere is below the ambient value.
  • the control unit opens the valve in the bypass line.
  • the basic volume flow is therefore supplemented by an additional volume flow.
  • particle counters or a probe that works according to the photoelectric principle are suitable as the opacity probe.
  • the valve in the bypass line is a solenoid valve. This is opened and closed by the control unit depending on the current opacity value of the furnace atmosphere.
  • the protective gas volume flow can be continuously adapted to the current opacity value.
  • the valve in the bypass line is an engine valve.
  • problem-free measurement of the opacity is possible if the opacity probe is arranged in the exhaust pipe.
  • a shut-off valve 8, a flow meter 4, a regulating valve 11 and a further shut-off valve 9 are arranged in the flow direction of the protective gas.
  • a bypass line 18 is connected in parallel to the feed line 5, which branches off downstream of the shut-off valve 8 and opens again into the feed line before the shut-off valve 9.
  • Another flow meter 10 is arranged in the bypass line 18.
  • the furnace exhaust gas leaves the furnace via an exhaust line 17.
  • an opacity probe 2 is arranged in the exhaust gas line, in which the absorption capacity, that is to say the opacity of the furnace atmosphere, is measured and a measurement signal is formed.
  • the measurement signal is passed to a control unit 3.
  • control unit 3 is connected to an engine valve 13 in the bypass line 18.
  • cold-rolled steel strips are to be treated in the furnace 1 by bright or recrystallization annealing.
  • B three steel coils wound into a coil on the base of the furnace 1 and a retort lowered over the coils. A seal between the retort and base prevents excessive leak rates.
  • a protective gas consisting of nitrogen, to which, for example, 2.5% by volume of hydrogen is added, is passed via line 5 through the opened valves 8 and 9 into the furnace 1.
  • Valve 13 is still closed.
  • the volume flow is set with valve 11, in the exemplary embodiment to about 10 m 3 / h.
  • the protective gas flows through the furnace 1 in contact with the coil and leaves the furnace via the exhaust pipe 17 and via leaks in the furnace. Because of the leaks, it is important that the furnace is always supplied with a minimal amount of shielding gas, which covers the leakage losses through the base seal and - in older furnace models - the fan shaft bushing and thus protects the batch from oxidation.
  • the opacity probe 2 and control unit 3 are also switched on.
  • the opacity of the furnace exhaust gas at the beginning of the heating phase, the ambient value serves as the starting level for determining the setpoint of the opacity.
  • the opacity is determined, for example, on the basis of the weakening of a light beam that penetrates the furnace atmosphere.
  • a setpoint is set in the control unit, which is approximately 2% above the ambient value.
  • opacity probe 2 If the opacity of the furnace exhaust gas increases in the course of the heating phase due to evaporating rolling oil emulsion, this increase is detected by the opacity probe 2.
  • a control signal is sent to the engine valve 13 via a transducer and control unit 3 when the setpoint value is exceeded. With increasing opacity, the engine valve is opened further and further until a maximum volume flow of, for example, 20 m 3 / h is reached. With decreasing opacity, engine valve 13 always becomes continues to close until the opacity drops below the setpoint. From this point onwards, only the basic volume flow flowing through line 5 is flushed.
  • the embodiment according to FIG. 2 differs from that of FIG. 1 in that a magnetic valve 14 and a regulating valve 12 are arranged in the bypass line 18 instead of a motor valve.
  • control unit 3 opens solenoid valve 14 so that the volume flow set with control valve 12 flows through bypass line 18 and is mixed into the base volume flow.
  • shielding gas with a maximum volume flow eg 20 m 3 / h
  • the basic volume flow e.g. 10 m 3 / h
  • the process according to the invention makes it possible to achieve a considerable saving in protective gas, since the protective gas is only passed into the oven in the required quantities and at the times in which protective gas is actually used for purging.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Furnace Details (AREA)
  • Cookers (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)

Claims (13)

1. Procédé pour le recuit de parties métalliques, sous atmosphère contrôlée dans un four dans lequel le gaz de protection est introduit temporairement avec un débit volumétrique maximal, caractérisé en ce que le gaz de protection n'est amené dans le four avec un débit volumétrique maximal pendant la phase de mise en température qu'à l'intérieur d'un espace de temps durant lequel l'opacité de l'atmosphère du four est supérieure à celle de l'atmosphère du four à la température ambiante.
2. Procédé selon la revendication 1, caractérisé en ce que le gaz de protection est amené dans le four avec un débit volumétrique maximal seulement pendant un espace de temps durant lequel l'opacité de l'atmosphère du four est supérieure de 2 % et plus, de préférence 5 % et plus, à l'opacité du gaz de protection amené dans le four.
3. Procédé selon l'une des revendications 1 ou 2, caractérisé en ce que le gaz de protection consiste en azote et en une quantité réduite d'un gaz additionnel réducteur.
4. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que l'on mesure, de manière continue, l'opacité de l'atmosphère du four, on compare la valeur mesurée à une valeur de consigne et on alimente automatiquement le four en gaz de protection avec un débit volumétrique maximal aussi longtemps que l'opacité de l'atmosphère du four est supérieure à la valeur de consigne prescrite.
5. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que l'on mesure, de manière continue, l'opacité de l'atmosphère du four, et, en ce qu'à partir d'une comparaison du signal mesuré avec la valeur de consigne, on délivre un ordre de réglage pour augmenter ou diminuer l'alimentation en gaz de protection dans le sens d'une égalisation de la valeur d'opacité mesurée à la valeur de consigne.
6. Procédé selon l'une des revendications 4 ou 5, caractérisé en ce que l'on mesure l'opacité du gaz d'échappement du four.
7. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que le gaz de protection est amené au four avec un débit volumétrique maximal selon un programme qui est commandé en fonction du temps, ce programme étant donné par les variations d'opacité préalablement déterminées.
8. Dispositif pour la mise en oeuvre du procédé selon l'une des revendications 1 à 6, avec un four de recuit dans lequel débouchent une canalisation d'alimentation et une canalisation d'évacuation, caractérisé par un capteur d'opacité (2) exposé à t'atmosphère formée dans le four (1) et raccordé à une unité de régulation (3) ainsi que par, disposée en parallèle à la canalisation d'alimentation (5) pour le débit volumétrique de base, une canalisation by-pass (18) pour le débit volumétrique additionnel avec une vanne (13, 14) associée à l'unité de régulation (3).
9. Dispositif selon la revendication 8, caractérisé en ce que la vanne est une électrovanne (14).
10. Dispositif selon la revendication 8, caractérisé en ce que la vanne est une vanne motorisée (13).
11. Dispositif selon l'une des revendications 8 à 10, caractérisé en ce que le capteur d'opacité (2) est disposé dans la canalisation d'échappement (17).
12. Application du procédé et du dispositif selon les revendications 1 à 11 aux recuits blancs et/ou de recristallisation d'acier laminé à froid dans des fours à cloche.
13. Application du procédé et du dispositif selon l'une des revendications 1 à 11 aux recuits de rouleaux semi-finis et de produits semi-finis en métaux non ferreux.
EP85101547A 1984-02-24 1985-02-13 Procédé et dispositif pour le recuit de pièces métalliques Expired EP0156147B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85101547T ATE28480T1 (de) 1984-02-24 1985-02-13 Verfahren und vorrichtung zum gluehen von metallteilen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3406792 1984-02-24
DE19843406792 DE3406792A1 (de) 1984-02-24 1984-02-24 Verfahren und vorrichtung zum gluehen von metallteilen

Publications (2)

Publication Number Publication Date
EP0156147A1 EP0156147A1 (fr) 1985-10-02
EP0156147B1 true EP0156147B1 (fr) 1987-07-22

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EP85101547A Expired EP0156147B1 (fr) 1984-02-24 1985-02-13 Procédé et dispositif pour le recuit de pièces métalliques

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EP (1) EP0156147B1 (fr)
AT (1) ATE28480T1 (fr)
AU (1) AU572259B2 (fr)
BR (1) BR8500773A (fr)
DE (2) DE3406792A1 (fr)
ZA (1) ZA851358B (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69215613T2 (de) * 1991-09-10 1997-05-15 Nippon Steel Corp Verfahren zum Kontrollieren des Aufheizens eines Legierungsofens zum Herstellen von heiss-tauchmetallisiertem und legiertem Stahlband
DE4241746C1 (de) * 1992-12-11 1994-08-25 Messer Griesheim Gmbh Verfahren zum rußfreien Glühen von Stahlband in einem Glühofen
ES2133126B1 (es) 1997-11-14 2000-04-01 Al Air Liquide Espana S A Procedimiento perfeccionado para el recocido de rollos de acero al carbono trefilado y bobinas de chapa de acero al carbono.
DE10232432A1 (de) * 2002-07-17 2004-01-29 Linde Ag Verfahren und Vorrichtung zum Unterdruckaufkohlen
DE102005045466B4 (de) * 2005-09-22 2015-10-29 Volkswagen Ag Verfahren zur Behandlung von Stahlband
DE102006032617B4 (de) * 2006-07-12 2008-04-03 Universität Kassel Verfahren zur Herstellung eines zum Formhärten geeigneten Blechhalbzeugs

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT395321B (de) * 1983-07-05 1992-11-25 Ebner Ind Ofenbau Verfahren zum abkuehlen von chargen in diskontinuierlich arbeitenden industrieoefen, insbesondere von stahldraht- oder - bandbunden in haubengluehoefen

Also Published As

Publication number Publication date
DE3406792A1 (de) 1985-08-29
DE3560367D1 (en) 1987-08-27
BR8500773A (pt) 1985-10-08
AU3848685A (en) 1985-08-29
AU572259B2 (en) 1988-05-05
ZA851358B (en) 1985-10-30
ATE28480T1 (de) 1987-08-15
EP0156147A1 (fr) 1985-10-02

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