EP0407254A1 - Process for thermal treating of metals - Google Patents
Process for thermal treating of metals Download PDFInfo
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- EP0407254A1 EP0407254A1 EP90401720A EP90401720A EP0407254A1 EP 0407254 A1 EP0407254 A1 EP 0407254A1 EP 90401720 A EP90401720 A EP 90401720A EP 90401720 A EP90401720 A EP 90401720A EP 0407254 A1 EP0407254 A1 EP 0407254A1
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- Prior art keywords
- high temperature
- zone
- upstream
- heat treatment
- nitrogen
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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
- 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
- C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
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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
Definitions
- the invention relates to the thermal treatment of metals by continuous passage of metallic parts in an elongated zone under a controlled atmosphere having an upstream part at high temperature where said controlled atmosphere comprises nitrogen and reducing chemical species, in particular hydrogen, possibly carbon monoxide and a downstream part at a lower temperature under an atmosphere.
- This type of controlled atmosphere which is mainly used for the annealing of metal parts, has so far been produced as follows: - Either an exothermic generator is used ensuring the incomplete combustion of a hydrocarbon and air and delivering combustion gases which, after possible purification, contain hydrogen and carbon monoxide, both of which are reducing to respective contents which depend on the air / hydrocarbon ratio admitted into the generator.
- an exothermic atmosphere can contain from 5 to 10% of carbon monoxide and 6 to 12% of hydrogen.
- - Either a synthetic atmosphere is produced from pure industrial gases such as nitrogen and hydrogen. Nitrogen is produced by cryogenic distillation of air and contains very few impurities; for example, the total of water vapor and oxygen impurities is generally less than 10 vpm. To this very pure nitrogen is added hydrogen, or a hydrocarbon, or hydrogen and a hydrocarbon, or methanol so as to produce a reducing atmosphere and, where appropriate, non-decarburizing to treat the metal parts.
- cryogenic by nitrogen produced by air separation using adsorption or selective permeation techniques which, under certain production conditions, lead to significantly reduced costs compared to cryogenic nitrogen, to the detriment, however, of impurity oxygen since the nitrogen produced by adsorption usually contains a residual oxygen content of 0.5% to 5% whereas the residual oxygen content of the nitrogen produced by permeation generally exceeds 3% and can range up to 10%.
- the present invention relates to a process for heat treatment of metals which makes it possible to substantially reduce the cost of the treatment atmosphere while ensuring the qualities required of said atmosphere which must be devoid of oxygen both in the upstream part at high temperature and in the downstream part at lower temperature and this process according to the invention is characterized in that in the upstream part at high temperature the nitrogen constituting the atmosphere is supplied by admission of nitrogen with residual oxygen content not exceeding not 5% and preferably greater than 0.5% produced by air separation according to permeation or adsorption techniques, the said reducing species being at all times present in contents at least sufficient to eliminate the oxygen thus admitted with nitrogen, while the controlled atmosphere partly downstream of said elongated heat treatment zone is formed by admitting sion of a gas flow taken from the upstream part at high temperature and directly transferred into said downstream part at lower temperature.
- the high temperature zone by adding or creating in situ in sufficient quantities reducing species such as hydrogen and carbon monoxide, it ensures the almost instantaneous and almost complete elimination of the oxygen admitted. with nitrogen by transformation into water vapor and carbon dioxide, while maintaining, if necessary, a sufficient content of said reducing species so that the H rapports / H2O and CO / CO2 ratios remain within the limits suitable for times to ensure the required treatment effect without causing the oxidation of the parts being treated.
- this problem is circumvented by taking an appropriate flow rate from the zone. at high temperature which is simply transferred to the lower temperature zone.
- the flow rate taken from the upstream part at high temperature is between 2% and 75% of the overall flow rate admitted in the upstream part at high temperature.
- the flow rate taken from the upstream part at high temperature is between 2% and 35% of the overall flow rate admitted in the upstream part at high temperature.
- the flow rate taken from the upstream part at high temperature is between 25% and 75% of the overall flow rate admitted in the upstream part at high temperature.
- the elongated zone is a continuous zone with an upstream part at high temperature and a downstream part for cooling.
- the elongated zone is discontinuous and comprises a part of upstream zone at high temperature and a part of downstream zone at lower temperature and according to a more particular form of application, the zone of treatment upstream at temperature high and the lower temperature downstream zone are separated from each other by a treatment station outside of a controlled atmosphere, for example in a liquid bath.
- the sampling of the gas flow out of the upstream zone at high temperature to transfer it to the downstream zone at lower temperature is carried out downstream of a gas inlet point constituting said controlled atmosphere in high temperature zone and preferably the removal of the gas flow out of the upstream zone at high temperature to transfer it to the downstream zone at lower temperature takes place between two points 'admission of constituent gases of said controlled atmosphere in high temperature zone.
- the invention relates more particularly to certain following examples of implementation which are detailed by way of illustration.
- the sheet is subjected here to heating before quenching at 950 ° C. in a high temperature upstream treatment zone formed by a first furnace.
- the strip is then quenched at the outlet of the first furnace in a bath of liquid lead before undergoing tempering at 400 ° C. in a second treatment zone formed by a second furnace.
- - 30 m3 / h of atmosphere is admitted at two points spaced from the first oven.
- This atmosphere is composed of 70% nitrogen obtained by permeation or adsorption (21 m3 / h) with a residual oxygen of O.5%, and 30% hydrogen (6 m3 / h) and CO ( 3 m3 / h) from the cracking of 5.3 l / h of vaporized methanol.
- the temperature of 950 ° C is sufficient to ensure proper cracking of methanol as well as the combination of residual oxygen with the reducing species present (H2 and CO).
- the temperature of 400 ° C. is insufficient and the tempering treatment with industrial gases would require the use of cryogenic nitrogen and hydrogen, which is difficult to accept from an economic point of view.
- the treatment atmosphere of the first oven is used in the second oven by withdrawing by extraction at an intermediate point (15 m3 / h) from the atmosphere of the first oven (i.e. 50% of the total must injected ) to inject it into the second oven.
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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)
- Separation Of Gases By Adsorption (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
Procédé de traitement thermique de métaux par passage de pièces métalliques dans une zone allongée sous atmosphère contrôlée présentant une partie amont à température élevée où ladite atmosphère contrôlée comprend de l'azote et des espèces chimiques réductrices, notamment de l'hydrogène, éventuellement du monoxyde de carbone et une partie aval à température plus faible, caractérisé en ce que dans la partie amont à température élevée l'azote de constitution de l'atmosphère est fourni par admission d'azote à teneur résiduelle en oxygène entre 0,5 % et 5 % élaboré par séparation d'air selon les techniques de perméation ou d'adsorption, les dites espèces réductrices étant à tout moment présentes en teneurs au moins suffisantes pour éliminer l'oxygène ainsi admis avec l'azote, tandis que l'atmosphère contrôlée en partie aval de ladite zone allongée de traitement thermique est formée par admission d'un débit gazeux prélevé de la partie amont à température élevée et directement transféré dans ladite partie aval à température plus faible.Process for the thermal treatment of metals by passing metal parts through an elongated zone under a controlled atmosphere having an upstream portion at high temperature where said controlled atmosphere comprises nitrogen and reducing chemical species, in particular hydrogen, optionally carbon monoxide carbon and a downstream part at lower temperature, characterized in that in the upstream part at high temperature the nitrogen constituting the atmosphere is supplied by admission of nitrogen with residual oxygen content between 0.5% and 5% produced by air separation according to permeation or adsorption techniques, the said reducing species being present at all times in contents at least sufficient to eliminate the oxygen thus admitted with nitrogen, while the atmosphere partly controlled downstream of said elongated heat treatment zone is formed by admission of a gas flow taken from the amo part nt at high temperature and directly transferred into said downstream part at lower temperature.
Description
L'invention concerne le traitement thermique de métaux par passage continu de pièces métalliques dans une zone allongée sous atmosphère contrôlée présentant une partie amont à température élevée où ladite atmosphère contrôlée comprend de l'azote et des espèces chimiques réductrices, notamment de l'hydrogène, éventuellement du monoxyde de carbone et une partie aval à température plus faible sous atmosphère.The invention relates to the thermal treatment of metals by continuous passage of metallic parts in an elongated zone under a controlled atmosphere having an upstream part at high temperature where said controlled atmosphere comprises nitrogen and reducing chemical species, in particular hydrogen, possibly carbon monoxide and a downstream part at a lower temperature under an atmosphere.
Ce type d'atmosphère contrôlée qui est essentiellement utilisée pour le recuit de pièces métalliques est jusqu'à maintenant produit de la façon suivante :
- soit on utilise un générateur exothermique assurant la combustion incomplète d'un hydrocarbure et de l'air et délivrant des gaz de combustion qui, après épuration éventuelle, contiennent de l'hydrogène et du monoxyde de carbone tous deux réducteurs à des teneurs respectives qui dépendent du rapport air/hydrocarbure admis dans le générateur. A titre d'exemple, une telle atmosphère exothermique peut contenir de 5 à 10 % de monoxyde de carbone et 6 à 12 % d'hydrogène
- soit on réalise une atmosphère synthétique à partir de gaz industriels purs tels que l'azote et l'hydrogène. L'azote est produit par distillation cryogénique de l'air et contient très peu d'impuretés ; par exemple le total des impuretés vapeur d'eau et oxygène est généralement inférieur à 10 vpm. On adjoint à cet azote très pur de l'hydrogène, ou un hydrocarbure, ou de l'hydrogène et un hydrocarbure, ou du méthanol de façon à produire une atmosphère réductrice et le cas échéant non décarburante pour traiter les pièces métalliques.This type of controlled atmosphere, which is mainly used for the annealing of metal parts, has so far been produced as follows:
- Either an exothermic generator is used ensuring the incomplete combustion of a hydrocarbon and air and delivering combustion gases which, after possible purification, contain hydrogen and carbon monoxide, both of which are reducing to respective contents which depend on the air / hydrocarbon ratio admitted into the generator. For example, such an exothermic atmosphere can contain from 5 to 10% of carbon monoxide and 6 to 12% of hydrogen.
- Either a synthetic atmosphere is produced from pure industrial gases such as nitrogen and hydrogen. Nitrogen is produced by cryogenic distillation of air and contains very few impurities; for example, the total of water vapor and oxygen impurities is generally less than 10 vpm. To this very pure nitrogen is added hydrogen, or a hydrocarbon, or hydrogen and a hydrocarbon, or methanol so as to produce a reducing atmosphere and, where appropriate, non-decarburizing to treat the metal parts.
Cette seconde façon de faire a l'avantage de maîtriser complètement la qualité de l'atmosphère de traitement mais présente l'inconvénient de mettre en oeuvre de l'azote cryogénique qui est relativement onéreux. C'est la raison pour laquelle on a été conduit à tenter de réduire les débits de gaz admis en créant notamment en sortie de la zone de refroidissement un tampon d'azote qui permet d'éviter toute remontée d'air au travers de la zone de refroidissement assurant ainsi une réduction significative du débit global admis. Malgré cette réduction de débit importante, il s'est avéré que les gaz industriellement purs sont encore loin d'être économiquement attractifs par rapport aux gaz produits par un générateur exothermique.This second way of doing things has the advantage of completely controlling the quality of the treatment atmosphere but has the drawback of using cryogenic nitrogen which is relatively expensive. This is the reason why we have been led to try to reduce the admitted gas flow rates by creating in particular at the outlet of the cooling zone a nitrogen buffer which makes it possible to avoid any rise of air through the zone. cooling thus ensuring a significant reduction in the overall flow admitted. Despite this significant reduction in flow, it has been found that industrially pure gases are still far from being economically attractive compared to gases produced by an exothermic generator.
C'est la raison pour laquelle, dans certaines applications où cela s'est avéré possible, on a proposé de remplacer l'azote cryogénique par de l'azote produit par séparation d'air selon les techniques d'adsorption ou de perméation sélective qui, dans certaines conditions de production, conduisent à des coûts nettement réduits par rapport à l'azote cryogénique au détriment cependant de l'impureté oxygène puisque l'azote produit par adsorption contient usuellement une teneur résiduelle en oxygène de 0,5 % à 5 % alors que la teneur résiduelle en oxygène de l'azote produit par perméation dépasse généralement 3 % et peut aller jusqu'à 10 %.This is the reason why, in certain applications where this has proved possible, it has been proposed to replace nitrogen. cryogenic by nitrogen produced by air separation using adsorption or selective permeation techniques which, under certain production conditions, lead to significantly reduced costs compared to cryogenic nitrogen, to the detriment, however, of impurity oxygen since the nitrogen produced by adsorption usually contains a residual oxygen content of 0.5% to 5% whereas the residual oxygen content of the nitrogen produced by permeation generally exceeds 3% and can range up to 10%.
Cette impureté oxygène rend très difficile l'utilisation directe de cet azote brut pour élaborer une atmosphère de traitement thermique convenable. En pratique, on a proposé l'azote produit selon le procédé de perméation sélective uniquement pour la production d'atmosphères réalisées à partir d'azote et de méthanol, comme cela est décrit dans l'article "Heat treating processess with nitrogen and methanol based atmosphere" M. KOSTELITZ and al. dans "Journal of Heat trating" volume 2 N° 1 - 35 et dans les brevets français 79.05.599, 82.12.380 et 85.12.379 au nom de la demanderesse. Une telle atmosphère réalisée à partir d'azote à teneur résiduelle en oxygène et de méthanol peut en effet être utilisée théoriquement dans différentes applications, à savoir le chauffage avant trempe, la carbonitruration et la cémentation d'acier. Mais ce n'est que dans ce dernier domaine que l'utilisation d'azote à teneur résiduelle en oxygène a reçu une utilisation industrielle et cela du fait de la température élevée, de l'ordre de 900°C, que la cémentation implique, cette température favorisant la réaction de l'oxygène résiduel véhiculé par l'azote avec les espèces chimiques de type hydrocarbures admis simultanément pour former l'atmosphère de base.This oxygen impurity makes it very difficult to directly use this crude nitrogen to develop a suitable heat treatment atmosphere. In practice, the nitrogen produced according to the selective permeation process has been proposed only for the production of atmospheres produced from nitrogen and methanol, as described in the article "Heat treating processess with nitrogen and methanol based atmosphere "M. KOSTELITZ and al. in "Journal of Heat trating" volume 2 N ° 1 - 35 and in French patents 79.05.599, 82.12.380 and 85.12.379 in the name of the applicant. Such an atmosphere produced from nitrogen with residual oxygen content and methanol can in fact be used theoretically in different applications, namely heating before quenching, carbonitriding and carburizing of steel. But it is only in this latter field that the use of nitrogen with residual oxygen content has received industrial use and this because of the high temperature, of the order of 900 ° C., that case hardening implies, this temperature favoring the reaction of the residual oxygen conveyed by the nitrogen with the chemical species of hydrocarbon type admitted simultaneously to form the basic atmosphere.
On a bien envisagé de purifier l'azote à teneur résiduelle en oxygène produit par adsorption ou perméation en faisant réagir par voie catalytique l'oxygène avec un apport correspondant d'hydrogène suffisant pour assurer l'élimination complète de tout l'oxygène, mais ce procédé relativement onéreux conduit à un coût de production voisin de l'azote cryogénique, ce qui défavorise cette forme d'elaboration d'azote pur, d'autant plus que la production d'azote par adsorption ou perméation ne présente pas les avantages de souplesse et de simplicité de la production de l'azote cryogénique.It has been envisaged to purify the nitrogen with residual oxygen content produced by adsorption or permeation by reacting catalytically the oxygen with a corresponding supply of hydrogen sufficient to ensure the complete elimination of all the oxygen, but this relatively expensive process leads to a production cost close to cryogenic nitrogen, which disadvantages this form of production of pure nitrogen, especially since the production of nitrogen by adsorption or permeation does not have the flexibility advantages and simplicity of cryogenic nitrogen production.
La présente invention vise un procédé de traitement thermique des métaux qui permet de réduire substantiellement le coût de l'atmosphère de traitement tout en assurant les qualités requises de ladite atmosphère qui doit être dépourvue d'oxygène aussi bien dans la partie amont à température élevée que dans la partie aval à température plus faible et ce procédé selon l'invention est caractérisé en ce que dans la partie amont à température élevée l'azote de constitution de l'atmosphère est fourni par admission d'azote à teneur résiduelle en oxygène ne dépassant pas 5 % et de préférence supérieure à 0,5 % élaboré par séparation d'air selon les techniques de perméation ou d'adsorption, les dites espèces réductrices étant à tout moment présentes en teneurs au moins suffisantes pour éliminer l'oxygène ainsi admis avec l'azote, tandis que l'atmosphère contrôlée en partie aval de ladite zone allongée de traitement thermique est formée par admission d'un débit gazeux prélevé de la partie amont à température élevée et directement transféré dans ladite partie aval à température plus faible. Ainsi, dans la zone à haute température, en adjoignant ou en créant in situ en quantités suffisantes des espèces réductrices telles que l'hydrogène et le monoxyde de carbone, on assure l'élimination quasi-instantanée et quasi-complète de l'oxygène admis avec l'azote par transformation en vapeur d'eau et en gaz carbonique, tout en maintenant, si besoin est, une teneur suffisante en les dites espèces réductrices pour que les rapports H₂/H₂O et CO/CO₂ restent dans les limites convenables à la fois pour assurer l'effet de traitement requis sans pour autant provoquer l'oxydation des pièces en cours de traitement. Dans la zone à température moins élevée, nettement plus faible et en tout cas insuffisante pour assurer la réaction immédiate entre l'oxygène résiduel véhiculé par l'azote et les espèces réductrices éventuellement présentes, on contourne cette difficulté en prélevant un débit approprié de la zone à température élevée que l'on transfère purement et simplement dans la zone à température moins élevée.The present invention relates to a process for heat treatment of metals which makes it possible to substantially reduce the cost of the treatment atmosphere while ensuring the qualities required of said atmosphere which must be devoid of oxygen both in the upstream part at high temperature and in the downstream part at lower temperature and this process according to the invention is characterized in that in the upstream part at high temperature the nitrogen constituting the atmosphere is supplied by admission of nitrogen with residual oxygen content not exceeding not 5% and preferably greater than 0.5% produced by air separation according to permeation or adsorption techniques, the said reducing species being at all times present in contents at least sufficient to eliminate the oxygen thus admitted with nitrogen, while the controlled atmosphere partly downstream of said elongated heat treatment zone is formed by admitting sion of a gas flow taken from the upstream part at high temperature and directly transferred into said downstream part at lower temperature. Thus, in the high temperature zone, by adding or creating in situ in sufficient quantities reducing species such as hydrogen and carbon monoxide, it ensures the almost instantaneous and almost complete elimination of the oxygen admitted. with nitrogen by transformation into water vapor and carbon dioxide, while maintaining, if necessary, a sufficient content of said reducing species so that the H rapports / H₂O and CO / CO₂ ratios remain within the limits suitable for times to ensure the required treatment effect without causing the oxidation of the parts being treated. In the zone with a lower temperature, clearly lower and in any case insufficient to ensure the immediate reaction between the residual oxygen conveyed by the nitrogen and the reducing species possibly present, this problem is circumvented by taking an appropriate flow rate from the zone. at high temperature which is simply transferred to the lower temperature zone.
Selon l'invention, le débit prélevé de la partie amont à température élevée est compris entre 2 % et 75 % du débit global admis en partie amont à température élevée.According to the invention, the flow rate taken from the upstream part at high temperature is between 2% and 75% of the overall flow rate admitted in the upstream part at high temperature.
Selon une mise en oeuvre, le débit prélevé de la partie amont à température élevée est compris entre 2 % et 35 % du débit global admis en partie amont à température élevée.According to one implementation, the flow rate taken from the upstream part at high temperature is between 2% and 35% of the overall flow rate admitted in the upstream part at high temperature.
Selon une autre mise en oeuvre le débit prélevé de la partie amont à température élevée est compris entre 25 % et 75 % du débit global admis en partie amont à température élevée.According to another implementation, the flow rate taken from the upstream part at high temperature is between 25% and 75% of the overall flow rate admitted in the upstream part at high temperature.
Dans une forme d'application, la zone allongée est une zone continue avec une partie amont à température élevée et une partie aval de refroidissement.In one form of application, the elongated zone is a continuous zone with an upstream part at high temperature and a downstream part for cooling.
Dans une autre forme d'application, la zone allongée est discontinue et comprend une partie de zone amont à température élevée et une partie de zone aval à température moins élevée et selon une forme d'application plus particulière, la zone de traitement amont à température élevée et la zone aval à température moins élevée sont séparées entre elles par un poste de traitement hors atmosphère contrôlée, par exemple en bain liquide.In another form of application, the elongated zone is discontinuous and comprises a part of upstream zone at high temperature and a part of downstream zone at lower temperature and according to a more particular form of application, the zone of treatment upstream at temperature high and the lower temperature downstream zone are separated from each other by a treatment station outside of a controlled atmosphere, for example in a liquid bath.
De préférence et quelle que soit les formes de mise en oeuvre d'application, le prélèvement du débit gazeux hors de la zone amont à température élevée pour le transférer dans la zone aval à température moins élevée s'effectue à l'aval d'un point d'admission de gaz constitutif de ladite atmosphère contrôlée en zone à température élevée et de préférence le prélèvement du débit gazeux hors de la zone amont à température élevée pour le transférer dans la zone aval à température moins élevée s'effectue entre deux points d'admission de gaz constitutifs de ladite atmosphère contrôlée en zone à température élevée.Preferably and whatever the forms of implementation of the application, the sampling of the gas flow out of the upstream zone at high temperature to transfer it to the downstream zone at lower temperature is carried out downstream of a gas inlet point constituting said controlled atmosphere in high temperature zone and preferably the removal of the gas flow out of the upstream zone at high temperature to transfer it to the downstream zone at lower temperature takes place between two points 'admission of constituent gases of said controlled atmosphere in high temperature zone.
L'invention concerne plus particulièrement certains exemples de mise en oeuvre suivants qui sont détaillés à titre illustratif.The invention relates more particularly to certain following examples of implementation which are detailed by way of illustration.
- On admet 60 m³/h en plusieurs points de la zone amont à température élevée d'un four. Une proportion (70 %) de ce débit (soit 42 m³/h) est de l'azote obtenu par perméation ou adsorption avec un résiduel d'oxygène de 0,5 %, tandis que les 30 % restants (soit 18 m³/h) sont constitués par 12 m³/h d'hydrogène et 6 m³/h de monoxyde de carbone provenant du craquage de 10,6 l/h de méthanol admis avec l'azote.
- on prélève de ladite zone à température élevée 5 m³/h (8,3 % du débit global) par un piquage situé entre deux points d'injection, puis on les achemine et on les réinjecte en sortie du four afin d'éviter toute oxydation en zone de refroidissement.- 60 m³ / h is allowed at several points in the upstream zone at high temperature of an oven. A proportion (70%) of this flow (i.e. 42 m³ / h) is nitrogen obtained by permeation or adsorption with a residual oxygen of 0.5%, while the remaining 30% (i.e. 18 m³ / h ) consist of 12 m³ / h of hydrogen and 6 m³ / h of carbon monoxide from the cracking of 10.6 l / h of methanol admitted with nitrogen.
- from this high temperature zone, 5 m³ / h (8.3% of the total flow) is withdrawn by a nozzle situated between two injection points, then they are conveyed and reinjected at the outlet of the oven in order to avoid any oxidation in the cooling zone.
La tôle subit ici un chauffage avant trempe à 950°C dans une zone de traitement amont à température élevée formée par un premier four. La bande est ensuite trempée en sortie du premier four dans un bain de plomb liquide avant de subir un revenu à 400°C dans une seconde zone de traitement formée par un second four.
- on admet 30 m³/h d'atmosphère en deux points espacés du premier four. Cette atmosphère est composée à 70 % d'azote obtenu par perméation ou adsorption (21 m³/h) avec un résiduel d'oxygène de O.5 %, et à 30 % d'hydrogène (6 m³/h) et de CO (3 m³/h) provenant du craquage de 5,3 l/h de méthanol vaporisé. La température de 950°C est suffisante pour assurer un craquage correct du méthanol ainsi que la combinaison de l'oxygène résiduel avec les espèces réductrices présentes (H₂ et CO). Dans le second four, en revanche, la température de 400°C est insuffisante et le traitement de revenu par les gaz industriels nécessiterait l'emploi d'azote cryogénique et d'hydrogène, ce qui est difficilement acceptable du point de vue économique.The sheet is subjected here to heating before quenching at 950 ° C. in a high temperature upstream treatment zone formed by a first furnace. The strip is then quenched at the outlet of the first furnace in a bath of liquid lead before undergoing tempering at 400 ° C. in a second treatment zone formed by a second furnace.
- 30 m³ / h of atmosphere is admitted at two points spaced from the first oven. This atmosphere is composed of 70% nitrogen obtained by permeation or adsorption (21 m³ / h) with a residual oxygen of O.5%, and 30% hydrogen (6 m³ / h) and CO ( 3 m³ / h) from the cracking of 5.3 l / h of vaporized methanol. The temperature of 950 ° C is sufficient to ensure proper cracking of methanol as well as the combination of residual oxygen with the reducing species present (H₂ and CO). In the second oven, on the other hand, the temperature of 400 ° C. is insufficient and the tempering treatment with industrial gases would require the use of cryogenic nitrogen and hydrogen, which is difficult to accept from an economic point of view.
Selon l'invention, on utilise dans le second four l'atmosphère de traitement du premier four en prélevant par l'extraction en un point intermédiaire (15 m³/h) de l'atmosphère du premier four (soit 50 % du doit total injecté) pour l'injecter dans le second four.According to the invention, the treatment atmosphere of the first oven is used in the second oven by withdrawing by extraction at an intermediate point (15 m³ / h) from the atmosphere of the first oven (i.e. 50% of the total must injected ) to inject it into the second oven.
Claims (12)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8908877A FR2649124A1 (en) | 1989-07-03 | 1989-07-03 | PROCESS FOR THE HEAT TREATMENT OF METALS UNDER ATMOSPHERE |
| FR8908877 | 1989-07-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0407254A1 true EP0407254A1 (en) | 1991-01-09 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP90401720A Withdrawn EP0407254A1 (en) | 1989-07-03 | 1990-06-19 | Process for thermal treating of metals |
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| Country | Link |
|---|---|
| US (1) | US5057164A (en) |
| EP (1) | EP0407254A1 (en) |
| FR (1) | FR2649124A1 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5320818A (en) * | 1992-12-22 | 1994-06-14 | Air Products And Chemicals, Inc. | Deoxygenation of non-cryogenically produced nitrogen with a hydrocarbon |
| US5298090A (en) * | 1992-12-22 | 1994-03-29 | Air Products And Chemicals, Inc. | Atmospheres for heat treating non-ferrous metals and alloys |
| US5284526A (en) * | 1992-12-22 | 1994-02-08 | Air Products And Chemicals, Inc. | Integrated process for producing atmospheres suitable for heat treating from non-cryogenically generated nitrogen |
| US5417774A (en) * | 1992-12-22 | 1995-05-23 | Air Products And Chemicals, Inc. | Heat treating atmospheres |
| US5348592A (en) * | 1993-02-01 | 1994-09-20 | Air Products And Chemicals, Inc. | Method of producing nitrogen-hydrogen atmospheres for metals processing |
| US5401339A (en) * | 1994-02-10 | 1995-03-28 | Air Products And Chemicals, Inc. | Atmospheres for decarburize annealing steels |
| US5441581A (en) * | 1994-06-06 | 1995-08-15 | Praxair Technology, Inc. | Process and apparatus for producing heat treatment atmospheres |
| US5968457A (en) * | 1994-06-06 | 1999-10-19 | Praxair Technology, Inc. | Apparatus for producing heat treatment atmospheres |
| IT1291205B1 (en) * | 1997-03-18 | 1998-12-29 | Rivoira S P A | PROCEDURE FOR THE GENERATION OF A PROTECTIVE ATMOSPHERE WITH LOW DEW POINT AND FREE FROM OXYGEN, FOR THE PERFORMANCE OF |
| US6168774B1 (en) | 1997-08-07 | 2001-01-02 | Praxair Technology, Inc. | Compact deoxo system |
| FR2805531B1 (en) * | 2000-02-24 | 2003-02-21 | Air Liquide | PROCESS FOR THE PRODUCTION OF HYDROGEN BY PARTIAL OXIDATION OF HYDROCARBONS |
| US6458217B1 (en) | 2000-02-29 | 2002-10-01 | American Air Liquide, Inc. | Superadiabatic combustion generation of reducing atmosphere for metal heat treatment |
| US6533996B2 (en) | 2001-02-02 | 2003-03-18 | The Boc Group, Inc. | Method and apparatus for metal processing |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1055569B (en) * | 1955-10-17 | 1959-04-23 | Walter Reinecken Dr Ing | Patenting system for elongated material, such as wires, pipes, bands, etc. |
| DE1063624B (en) * | 1957-07-25 | 1959-08-20 | Robert Von Linde Dipl Ing | Industrial furnace |
| US4139375A (en) * | 1978-02-06 | 1979-02-13 | Union Carbide Corporation | Process for sintering powder metal parts |
| EP0027649A1 (en) * | 1979-10-23 | 1981-04-29 | Air Products And Chemicals, Inc. | Protective atmosphere process for annealing and or spheroidizing ferrous metals |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4445945A (en) * | 1981-01-14 | 1984-05-01 | Holcroft & Company | Method of controlling furnace atmospheres |
| JPS59153842A (en) * | 1983-02-19 | 1984-09-01 | Kobe Steel Ltd | Production of steel wire rod having excellent scale detachability after annealing |
| JPS62136528A (en) * | 1985-12-09 | 1987-06-19 | Kawasaki Steel Corp | Production of thin stainless steel sheet |
-
1989
- 1989-07-03 FR FR8908877A patent/FR2649124A1/en not_active Withdrawn
-
1990
- 1990-06-19 EP EP90401720A patent/EP0407254A1/en not_active Withdrawn
- 1990-06-26 US US07/543,434 patent/US5057164A/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1055569B (en) * | 1955-10-17 | 1959-04-23 | Walter Reinecken Dr Ing | Patenting system for elongated material, such as wires, pipes, bands, etc. |
| DE1063624B (en) * | 1957-07-25 | 1959-08-20 | Robert Von Linde Dipl Ing | Industrial furnace |
| US4139375A (en) * | 1978-02-06 | 1979-02-13 | Union Carbide Corporation | Process for sintering powder metal parts |
| EP0027649A1 (en) * | 1979-10-23 | 1981-04-29 | Air Products And Chemicals, Inc. | Protective atmosphere process for annealing and or spheroidizing ferrous metals |
Non-Patent Citations (1)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN * |
Also Published As
| Publication number | Publication date |
|---|---|
| US5057164A (en) | 1991-10-15 |
| FR2649124A1 (en) | 1991-01-04 |
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