EP0532386B1 - Process and apparatus for carburizing steel in an atmosphere of low pressure - Google Patents
Process and apparatus for carburizing steel in an atmosphere of low pressure Download PDFInfo
- Publication number
- EP0532386B1 EP0532386B1 EP92402395A EP92402395A EP0532386B1 EP 0532386 B1 EP0532386 B1 EP 0532386B1 EP 92402395 A EP92402395 A EP 92402395A EP 92402395 A EP92402395 A EP 92402395A EP 0532386 B1 EP0532386 B1 EP 0532386B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- injection
- phase
- gas
- duration
- gas flow
- 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 - Lifetime
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
Definitions
- this treatment is carried out in a charge oven (or not) inside which the parts are brought to a treatment temperature in an atmosphere based on nitrogen and methanol.
- this oxygen reacts on the surface of the steel by phenomenon of intergranular oxidation.
- the latter weakens the surface structure by locally reducing the hardness and above all the fatigue limit.
- the oxygen present has the effect of limiting the transfer of carbon at the interface between the cementing gas phase and the solid to be cemented. This phenomenon therefore limits the rate of carburizing.
- carburizing equipment is often provided with an oxygen sensor and an infrared analyzer, so as to control the carbon potential in the atmosphere.
- the invention therefore more particularly aims to eliminate all these drawbacks.
- a case hardening process consisting in bringing the parts to be treated to a temperature of between 800 ° C. and 1100 ° C., in a gaseous atmosphere free of oxygen maintained by pumping at low pressure, and in carrying out a plurality of successive carbon enrichment phases, each obtained by an injection of limited duration, of a treatment gas comprising one or more pure hydrocarbons, each enrichment phase having a duration less than the time of transition to saturation phase of austenite, these enrichment phases being separated by longer diffusion phases under vacuum making it possible to adjust the surface carbon content.
- this process is characterized in that the above pressure is maintained at a value between 1 and 10 mbar with a gas flow such that the cementing atmosphere is saturated or has a high cementing potential, and in that the process gas injection phases are obtained by means of a plurality of injection nozzles implemented in a sequence making it possible to generate a moving gas flow on the parts to be treated.
- the main cementing agent is ethylene from "cracking", propane or ethane, methane being the least effective compound.
- Another important advantage of the process according to the invention consists in that it makes it possible to control the residence time of the gas in the furnace: As soon as the injection stops (which caused a rise in pressure), the gas is quickly found pumped until the pressure returns to its initial value at which the treatment gas content is negligible. It then becomes possible to avoid passing below the saturation threshold of austenite and the resulting drawbacks.
- the invention also relates to a device for implementing the method described above, this device involving a heat or thermochemical vacuum treatment oven, of the type comprising, inside a sealed enclosure connected to a pumping station, a thermally insulating muffle equipped with heating means, inside which the charges to be treated are arranged, and a plurality of means making it possible to inject a treatment gas inside the oven, the pumping being designed so as to be able to obtain inside the enclosure, a pressure of the order of 1 to 10 mbar, and the heating means being designed so as to carry the load disposed inside the oven, at a temperature between 800 ° C and 1100 ° C.
- the invention proposes a gas injection system which makes it possible to rotate the gas flow of hydrocarbon in the enclosure of the furnace whatever its geometry, and this, in order to cement any type of parts. , homogeneously, without introducing any complex mechanism in the hot part of the oven.
- the device according to the invention is characterized in that the injection means comprise a plurality of injection nozzles connected to respective solenoid valves controlled by a computer programmed so as to carry out injection phases having each a duration calculated so as to be less than the time of transition to the saturation phase of the austenitic phase of the steel brought to high temperature, each injection phase comprising a sequence of successive openings and closings of the solenoid valves, according to a pre-established sequence, causing a displacement of treatment gas flow on the parts to be treated.
- the above sequence may be designed so as to obtain an atmosphere of pulsating cementing gas, in permanent, circular or helical movement.
- the pressure inside the furnace (indicated in thick lines) is maintained by pumping at a relatively low value until an instant t1 which follows a phase P6 of thermal homogenization of the parts at the temperature treatment (for example 30 minutes after the temperature has reached the treatment temperature).
- a first carbon enrichment phase C1 is initiated, by carrying out a first injection of treatment gas, for a short duration (from 1 s to 5 min).
- This injection has the effect of slightly increasing the pressure for a period calculated so as to avoid exceeding the saturation threshold of the austenite. Due to the pumping of the injected gas, the pressure then quickly returns to its initial value (instant t2).
- the duration of this enrichment phase C1 is generally of the order of a few seconds to a few minutes.
- a first diffusion phase D am (diffusion of carbon towards the core of the steel) is initiated during which the temperature is maintained at the treatment temperature, and the atmosphere at low pressure does not contains almost more process gas to allow carbon enrichment.
- a second carbon enrichment phase C2 is triggered by carrying out a second injection of treatment gas.
- the duration of this second enrichment phase may be different from that of the first, provided that the saturation threshold previously mentioned is not exceeded.
- the treatment ends with the vacuum quenching using oil or pressurized gas (phase P5) which occurs (instant t5) after a diffusion phase D2 (instant t4) of a duration substantially equal to that of the diffusion phase D1.
- the temperature suddenly changes from the treatment temperature to the ambient temperature corresponding to the quenching operation of the steel or hardening of the case-hardened steel.
- the invention is not limited to the previously described treatment cycle:
- the number of enrichment phases and the number of diffusion phases could be greater than two depending on the desired cemented depth.
- FIG. 2 shows an installation capable of carrying out a cementation treatment at low pressure using a vacuum type heat treatment furnace of the bell type, that is to say comprising a sealed enclosure comprising a cylindrical body 1, oriented vertically and open in its lower part, this body being movable and mounted in a sealed and disconnectable manner on a circular base 2 forming the bottom of the oven on which the parts to be treated are placed.
- a vacuum type heat treatment furnace of the bell type that is to say comprising a sealed enclosure comprising a cylindrical body 1, oriented vertically and open in its lower part, this body being movable and mounted in a sealed and disconnectable manner on a circular base 2 forming the bottom of the oven on which the parts to be treated are placed.
- the body 1 contains a cylindrical muffle 3 made of refractory material, inside of which electrical heating resistors 4 are arranged making it possible to provide heating of the parts by radiation.
- the interior volume of the oven is connected to a suction circuit comprising a vacuum pump 5 controlled by a regulation circuit at least partially housed in a control cabinet 6.
- This control cabinet 6 also contains the usual electronic instruments such as displays or recorders as well as the device for programming and regulating the heating.
- the interior volume of the enclosure is connected to a treatment gas injection system comprising one or more (here, a source of propane and a source of nitrogen) gas sources G1, G2 connected to nozzles injection 7 which pass through the body 1 / muffle 3 assembly, by means of a circuit successively comprising a flow meter 8 and solenoid valves (block 9) each associated with one or more injection nozzles 7.
- a treatment gas injection system comprising one or more (here, a source of propane and a source of nitrogen) gas sources G1, G2 connected to nozzles injection 7 which pass through the body 1 / muffle 3 assembly, by means of a circuit successively comprising a flow meter 8 and solenoid valves (block 9) each associated with one or more injection nozzles 7.
- the oven comprises six groups of three nozzles (B1 to B18) arranged vertically one above the other, these groups being angularly offset by 60 ° with respect to each other ( Figures 3 and 4).
- FIG. 6 is an unrolled view of the cylindrical surface of the muffle 3, in which the locations of the injection nozzles B1 to B18 have been indicated, while FIG. 5 shows an embodiment of an injection circuit comprising nine solenoid valves E1 to E9, at the rate of one solenoid valve for two injection nozzles each belonging to two different groups.
- a microcomputer 11 suitably programmed so as to obtain, during the enrichment phases, a current of pulsating cementing gas in permanent movement.
- each solenoid valve can work for 2.77 hundredths of a second during a loop of duration of the order of 0.5 seconds.
- the cementing gas may, as for it has a speed of 1.48 m / s at the outlet of the injection nozzles.
- two additional solenoid valves E10 and E11 are provided at the outlet of the two sources G1, G2 so as to send into the injection circuit either the cementing gas (propane) or the neutral gas (nitrogen) used to clean the nozzles after each carburizing phase.
- FIG. 7 shows a mode of implantation of the injection nozzles in an oven of which the muffle 12 has simply been shown diagrammatically.
- the right and left lateral faces FD, FG of the muffle 12 are crossed by three batteries of five injection nozzles aligned horizontally on three respective levels, each nozzle being indicated by a point.
- the upper face FS of the muffle 12 is, for its part, traversed by three batteries of five injection nozzles oriented parallel to the batteries of the side faces.
- the nozzles of each of these faces are numbered from +1 to +18 in the order of their opening, during an injection cycle, it being understood that the solenoid valve which has the same number on each of the three faces of the oven opens at the same time and the sequence takes place in ascending order of the numbers.
- the gas injection speed at the outlet of the nozzles can be, here, of the order of 4.71 m / s.
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
Abstract
Description
D'une manière générale, on sait que l'un des principaux traitements de durcissement superficiel des aciers le plus usité actuellement dans le domaine de la mécanique générale est, sans conteste, la cémentation.In general, it is known that one of the main surface hardening treatments for steels that is most commonly used in the field of general mechanics is, without question, case hardening.
Ce traitement, qui est décrit notamment dans les brevets GB-A-1 510 481 et GB-A-1 559 690, permet d'augmenter la dureté de surface, les caractéristiques mécaniques, la limite de fatigue superficielle ou de roulement, et la tenue à l'usure d'organes mécaniques fortement sollicités comme les engrenages, les axes de transmission, les cames, etc...This treatment, which is described in particular in patents GB-A-1,510,481 and GB-A-1,559,690, makes it possible to increase the surface hardness, the mechanical characteristics, the limit of surface or rolling fatigue, and the wear resistance of highly stressed mechanical components such as gears, transmission shafts, cams, etc.
A l'heure actuelle, ce traitement est réalisé dans un four à charge (ou non) à l'intérieur duquel les pièces sont amenées à une température de traitement dans une atmosphère à base d'azote et de méthanol.At present, this treatment is carried out in a charge oven (or not) inside which the parts are brought to a treatment temperature in an atmosphere based on nitrogen and methanol.
Cette technique, qui est très diffusée, présente cependant un certain nombre d'inconvénients dus, en grande partie, à l'oxygène présent dans l'atmosphère cémentante.This technique, which is widely used, however has a number of drawbacks due, in large part, to the oxygen present in the cementing atmosphere.
En effet, cet oxygène réagit à la surface de l'acier par phénomène d'oxydation intergranulaire. Cette dernière fragilise la structure superficielle en diminuant localement la dureté et surtout la limite de fatigue.Indeed, this oxygen reacts on the surface of the steel by phenomenon of intergranular oxidation. The latter weakens the surface structure by locally reducing the hardness and above all the fatigue limit.
En outre, l'oxygène présent a pour effet de limiter le transfert du carbone au niveau de l'interface entre la phase gazeuse cémentante et le solide à cémenter. Ce phénomène limite donc la vitesse de cémentation.In addition, the oxygen present has the effect of limiting the transfer of carbon at the interface between the cementing gas phase and the solid to be cemented. This phenomenon therefore limits the rate of carburizing.
Pour remédier à ces inconvénients, les équipements de cémentation sont fréquemment pourvus de sonde à oxygène et d'analyseur à infra-rouge, de façon à contrôler le potentiel carbone dans l'atmosphère.To overcome these drawbacks, carburizing equipment is often provided with an oxygen sensor and an infrared analyzer, so as to control the carbon potential in the atmosphere.
Toutefois, bien que contrôlant la phase de cémentation, ces systèmes ne peuvent que limiter, mais sans cependant l'éliminer, l'effet néfaste de la présence de l'oxygène dans l'atmosphère de traitement. Par ailleurs, du point de vue mécanique, la couche superficielle présentant le phénomène d'oxydation intergranulaire, doit être généralement éliminée par de coûteuses opérations de rectification.However, although controlling the carburizing phase, these systems can only limit, but without eliminating it, the harmful effect of the presence of oxygen in the treatment atmosphere. Furthermore, from the mechanical point of view, the surface layer exhibiting the phenomenon of intergranular oxidation must generally be removed by costly rectification operations.
A ces inconvénients, s'ajoutent ceux résultant des particularités de la loi d'enrichissement en carbone d'un acier. Selon cette loi, l'enrichissement en carbone qui est linéaire en fonction du temps, en dessous du seuil de saturation de l'austénite, devient fonction de la racine carrée du temps au-delà de ce seuil (régime diffusionnel - loi de Fick).In addition to these drawbacks, there are those resulting from the peculiarities of the carbon enrichment law of a steel. According to this law, the carbon enrichment which is linear as a function of time, below the saturation threshold of austenite, becomes a function of the square root of time beyond this threshold (diffusion regime - Fick's law) .
Au cours de ce régime diffusionnel, il se produit un carbure de fer, très dur et très fragile appelé cémentite (Fe3C) ainsi que de la suie.During this diffusion regime, a very hard and very fragile iron carbide called cementite (Fe3C) is produced, as well as soot.
En outre, compte tenu du fait que les traitements sont effectués à la pression atmosphérique, et que la teneur en gaz de traitement est difficilement contrôlable avec précision, on constate :
- une hétérogénéité de traitement,
- un contrôle impossible de l'enrichissement,
- un taux de "cracking" très faible du gaz de traitement (en général du CH4) et un mauvais rendement en carbone bas.
- heterogeneity of treatment,
- impossible control of enrichment,
- a very low "cracking" rate of the treatment gas (generally CH4) and a poor low carbon yield.
Pour tenter d'éviter les effets néfastes de la surcarburation au cours du régime diffusionnel, on a proposé de réduire, au cours de cette phase, la teneur en gaz de traitement par dilution, en injectant dans le four un gaz neutre. Toutefois, cette solution ne permet pas d'obtenir une élimination totale du gaz de traitement et exige un temps relativement important pour réduire suffisamment le taux de gaz de traitement.In an attempt to avoid the harmful effects of overfilling during the diffusion regime, it has been proposed to reduce, during this phase, the content of treatment gas by dilution, by injecting a neutral gas into the furnace. However, this solution does not allow total elimination of the treatment gas and requires a relatively long time to sufficiently reduce the rate of treatment gas.
L'invention a donc plus particulièrement pour but de supprimer tous ces inconvénients.The invention therefore more particularly aims to eliminate all these drawbacks.
Elle propose, à cet effet, un procédé de cémentation consistant à porter les pièces à traiter à une température comprise entre 800°C et 1100°C, dans une atmosphère gazeuse exempte d'oxygène maintenue par pompage à basse pression, et à procéder à une pluralité de phases d'enrichissement en carbone successives, obtenues chacune par une injection de durée limitée, d'un gaz de traitement comprenant un ou plusieurs hydrocarbures purs, chaque phase d'enrichissement présentant une durée inférieure au temps de passage en phase de saturation de l'austénite, ces phases d'enrichissement étant séparées par des phases de diffusion sous vide de plus grande durée permettant d'ajuster la teneur superficielle en carbone.To this end, it proposes a case hardening process consisting in bringing the parts to be treated to a temperature of between 800 ° C. and 1100 ° C., in a gaseous atmosphere free of oxygen maintained by pumping at low pressure, and in carrying out a plurality of successive carbon enrichment phases, each obtained by an injection of limited duration, of a treatment gas comprising one or more pure hydrocarbons, each enrichment phase having a duration less than the time of transition to saturation phase of austenite, these enrichment phases being separated by longer diffusion phases under vacuum making it possible to adjust the surface carbon content.
Selon l'invention, ce procédé est caractérisé en ce que la susdite pression est maintenue à une valeur comprise entre 1 et 10 mbar avec un débit gazeux tel que l'atmosphère cémentante soit saturée ou présente un haut potentiel cémentant, et en ce que les phases d'injection de gaz de traitement sont obtenues au moyen d'une pluralité de buses d'injection mises en oeuvre selon une séquence permettant d'engendrer un flux gazeux en mouvement sur les pièces à traiter.According to the invention, this process is characterized in that the above pressure is maintained at a value between 1 and 10 mbar with a gas flow such that the cementing atmosphere is saturated or has a high cementing potential, and in that the process gas injection phases are obtained by means of a plurality of injection nozzles implemented in a sequence making it possible to generate a moving gas flow on the parts to be treated.
Le principe de ce procédé de cémentation repose sur les mécanismes de dissociation des hydrocarbures à la pression et à la température de traitement qui conduisent à obtenir des hydrocarbures plus simples et finalement du carbone et de l'hydrogène, les principales réactions étant :
- propane
-
- éthylène
-
- méthane
-
- éthane
-
- propane
-
- ethylene
-
- methane
-
- ethane
-
En fait, l'agent cémentant principal est l'éthylène issu du "cracking", du propane ou de l'éthane, le méthane étant le composé le moins efficace.In fact, the main cementing agent is ethylene from "cracking", propane or ethane, methane being the least effective compound.
Le procédé précédemment décrit (pression réduite/température élevée) permet de s'affranchir de la plupart des inconvénients des techniques antérieures, tout en permettant un accroissement des cinétiques de cémentation.The previously described process (reduced pressure / high temperature) overcomes most of the drawbacks of prior techniques, while allowing an increase in carburizing kinetics.
Grâce au fait que la génération de carbone actif est obtenue par simple dissociation de molécules d'hydrocarbure, le mécanisme du transfert de carbone est considérablement simplifié.Thanks to the fact that the generation of active carbon is obtained by simple dissociation of hydrocarbon molecules, the mechanism of carbon transfer is considerably simplified.
Ce phénomène de dissociation est amélioré, à basse pression, en raison de la loi de déplacement des équilibres (loi de Le Chatelier) : une baisse de pression à température constante, produit la réaction qui entraîne une augmentation de volume du système et inversement. On constate que ce processus tend à favoriser les réactions du type :
Un autre avantage important du procédé selon l'invention consiste en ce qu'il permet de contrôler le temps de séjour du gaz dans le four : Dès que cesse l'injection (qui a causé une élévation de pression), le gaz se trouve rapidement pompé jusqu'à ce que la pression retourne à sa valeur initiale à laquelle la teneur en gaz de traitement est négligeable. Il devient alors possible d'éviter le passage en dessous du seuil de saturation de l'austénite et les inconvénients qui en résultent.Another important advantage of the process according to the invention consists in that it makes it possible to control the residence time of the gas in the furnace: As soon as the injection stops (which caused a rise in pressure), the gas is quickly found pumped until the pressure returns to its initial value at which the treatment gas content is negligible. It then becomes possible to avoid passing below the saturation threshold of austenite and the resulting drawbacks.
En outre, les consommations de gaz de traitement sont réduites, tandis que la sécurité du système est améliorée.In addition, process gas consumption is reduced, while system security is improved.
Comme précédemment mentionné, l'invention concerne également un dispositif pour la mise en oeuvre du procédé précédemment décrit, ce dispositif faisant intervenir un four de traitement thermique ou thermochimique sous vide, du type comprenant, à l'intérieur d'une enceinte étanche connectée à une station de pompage, un moufle thermiquement isolant équipé de moyens de chauffage, à l'intérieur duquel sont disposées les charges à traiter, et une pluralité de moyens permettant d'injecter à l'intérieur du four un gaz de traitement, la station de pompage étant conçue de manière à pouvoir obtenir à l'intérieur de l'enceinte, une pression de l'ordre de 1 à 10 mbar, et les moyens de chauffage étant conçus de manière à porter la charge disposée à l'intérieur du four, à une température comprise entre 800°C et 1100°C.As previously mentioned, the invention also relates to a device for implementing the method described above, this device involving a heat or thermochemical vacuum treatment oven, of the type comprising, inside a sealed enclosure connected to a pumping station, a thermally insulating muffle equipped with heating means, inside which the charges to be treated are arranged, and a plurality of means making it possible to inject a treatment gas inside the oven, the pumping being designed so as to be able to obtain inside the enclosure, a pressure of the order of 1 to 10 mbar, and the heating means being designed so as to carry the load disposed inside the oven, at a temperature between 800 ° C and 1100 ° C.
Il s'avère que dans les installations classiques de ce type, une des difficultés majeures à résoudre est d'obtenir une homogénéité du traitement sur toutes les pièces d'une charge et sur toutes les formes de chacune de ces pièces.It turns out that in conventional installations of this type, one of the major difficulties to be resolved is to obtain homogeneity of the treatment on all the parts of a load and on all the shapes of each of these parts.
Pour atteindre cet objectif industriel, on a songé à faire tourner la charge contenant les pièces à traiter devant les buses d'injection d'hydrocarbure.To achieve this industrial objective, consideration has been given to rotating the load containing the parts to be treated in front of the hydrocarbon injection nozzles.
Toutefois, cette solution est délicate à mettre en oeuvre et manque de fiabilité industrielle en raison de la difficulté à mettre en rotation une charge portée à haute température.However, this solution is difficult to implement and lacks industrial reliability due to the difficulty of rotating a load brought to high temperature.
Afin de résoudre ce problème, l'invention propose un système d'injection de gaz qui permet de faire tourner le flux gazeux d'hydrocarbure dans l'enceinte du four quelle que soit sa géométrie, et ceci, afin de cémenter tout type de pièces, de façon homogène, sans introduire de mécanisme complexe en partie chaude du four.In order to solve this problem, the invention proposes a gas injection system which makes it possible to rotate the gas flow of hydrocarbon in the enclosure of the furnace whatever its geometry, and this, in order to cement any type of parts. , homogeneously, without introducing any complex mechanism in the hot part of the oven.
Pour parvenir à ce résultat, le dispositif selon l'invention est caractérisé en ce que les moyens d'injection comprennent une pluralité de buses d'injection connectées à des électrovannes respectives commandées par un calculateur programmé de manière à effectuer des phases d'injection présentant chacune une durée calculée de manière à être inférieure au temps de passage en phase de saturation de la phase austénitique de l'acier porté à haute température, chaque phase d'injection comprenant une séquence d'ouvertures et de fermetures successives des électrovannes, selon une séquence pré-établie, provoquant un déplacement de flux gazeux de traitement sur les pièces à traiter. La susdite séquence pourra être conçue de façon à obtenir une atmosphère de gaz cémentant pulsé, en mouvement permanent, circulaire ou hélicoïdal.To achieve this result, the device according to the invention is characterized in that the injection means comprise a plurality of injection nozzles connected to respective solenoid valves controlled by a computer programmed so as to carry out injection phases having each a duration calculated so as to be less than the time of transition to the saturation phase of the austenitic phase of the steel brought to high temperature, each injection phase comprising a sequence of successive openings and closings of the solenoid valves, according to a pre-established sequence, causing a displacement of treatment gas flow on the parts to be treated. The above sequence may be designed so as to obtain an atmosphere of pulsating cementing gas, in permanent, circular or helical movement.
Des modes d'exécution de l'invention seront décrits ci-après, à titre d'exemples non limitatifs, avec référence aux dessins annexés dans lesquels :
- La figure 1 est un diagramme de température et de pression en fonction du temps, d'un cycle de cémentation à basse pression, conforme au procédé selon l'invention ;
- La figure 2 est une représentation schématique d'une installation de traitement utilisant un four cloche ;
- Les figures 3 et 4 sont des vues (respectivement axiale et radiale) du moufle du four utilisé dans l'installation de la figure 2, ces vues montrant l'implantation des buses d'injection de gaz de traitement ;
- La figure 5 est une représentation schématique du circuit d'injection du gaz de traitement ;
- La figure 6 est une représentation illustrant une séquence d'ouverture/fermeture des électrovannes du circuit de la figure 5 ;
- La figure 7 est une vue schématique montrant un mode d'implantation des buses d'injection dans un four présentant un moufle parallélépipédique ;
- La figure 8 montre l'implantation des buses dans la paroi latérale gauche, la paroi supérieure, et la paroi latérale droite du moufle représenté figure 7.
- FIG. 1 is a diagram of temperature and pressure as a function of time, of a low pressure carburizing cycle, in accordance with the method according to the invention;
- FIG. 2 is a schematic representation of a treatment installation using a bell furnace;
- Figures 3 and 4 are views (respectively axial and radial) of the furnace muffle used in the installation of Figure 2, these views showing the location of the treatment gas injection nozzles;
- Figure 5 is a schematic representation of the process gas injection circuit;
- Figure 6 is a representation illustrating an opening / closing sequence of the solenoid valves of the circuit of Figure 5;
- Figure 7 is a schematic view showing a mode of implantation of the injection nozzles in an oven having a rectangular block;
- FIG. 8 shows the location of the nozzles in the left side wall, the upper wall, and the right side wall of the muffle shown in FIG. 7.
Tel que représenté sur la figure 1, le cycle thermique de cémentation comprend successivement :
- une première phase P₁ de montée en température allant de la température ambiante à une température de 760°C, cette élévation de température s'effectuant à une vitesse de 15°C/mn ;
- un premier palier P₂ (
par exemple de 1 heure) à la température de 760°C ; - une deuxième phase P₃ de montée en température amenant les pièces de la température du palier (760°C) à la température de traitement (ici de 980°C) ;
- une phase P₄ de maintien en température à la température de traitement ; et
- une phase P₅ de refroidissement pouvant consister par exemple en une trempe.
- a first phase P₁ of temperature rise going from room temperature to a temperature of 760 ° C, this temperature rise taking place at a speed of 15 ° C / min;
- a first stage P₂ (for example 1 hour) at the temperature of 760 ° C;
- a second temperature rise phase P₃ bringing the parts from the bearing temperature (760 ° C) to the treatment temperature (here 980 ° C);
- a phase P₄ of maintaining the temperature at the treatment temperature; and
- a cooling phase P₅ which may consist, for example, of quenching.
Au cours de ce cycle thermique, la pression à l'intérieur du four (indiquée en traits épais) est maintenue par pompage à une valeur relativement basse jusqu'à un instant t₁ qui suit une phase P₆ d'homogénéisation thermique des pièces à la température de traitement (par exemple 30 mn après que la température ait atteint la température de traitement).During this thermal cycle, the pressure inside the furnace (indicated in thick lines) is maintained by pumping at a relatively low value until an instant t₁ which follows a phase P₆ of thermal homogenization of the parts at the temperature treatment (for example 30 minutes after the temperature has reached the treatment temperature).
En effet, à l'instant t₁, on amorce une première phase C₁ d'enrichissement en carbone, en effectuant une première injection de gaz de traitement, pendant une courte durée (de 1 s à 5 mn). Cette injection a pour effet d'accroître légèrement la pression pendant une durée calculée de manière à éviter de dépasser le seuil de saturation de l'austénite. Du fait du pompage du gaz injecté, la pression retourne ensuite rapidement à sa valeur initiale (instant t₂). La durée de cette phase d'enrichissement C₁ est, en général, de l'ordre de quelques secondes à quelques minutes.Indeed, at time t₁, a first carbon enrichment phase C₁ is initiated, by carrying out a first injection of treatment gas, for a short duration (from 1 s to 5 min). This injection has the effect of slightly increasing the pressure for a period calculated so as to avoid exceeding the saturation threshold of the austenite. Due to the pumping of the injected gas, the pressure then quickly returns to its initial value (instant t₂). The duration of this enrichment phase C₁ is generally of the order of a few seconds to a few minutes.
A partir de l'instant t₂, on amorce une première phase de diffusion D₁ (diffusion du carbone vers le coeur de l'acier) au cours de laquelle la température est maintenue à la température de traitement, et l'atmosphère à basse pression ne contient pratiquement plus de gaz de traitement pour permettre un enrichissement en carbone.From the instant t₂, a first diffusion phase D am (diffusion of carbon towards the core of the steel) is initiated during which the temperature is maintained at the treatment temperature, and the atmosphere at low pressure does not contains almost more process gas to allow carbon enrichment.
A la fin de cette phase de diffusion D₁, instant t₃, on déclenche une seconde phase d'enrichissement en carbone C₂ en effectuant une seconde injection de gaz de traitement. La durée de cette deuxième phase d'enrichissement peut être différente de celle de la première, à condition qu'on ne dépasse pas le seuil de saturation précédemment évoqué.At the end of this diffusion phase D₁, instant t₃, a second carbon enrichment phase C₂ is triggered by carrying out a second injection of treatment gas. The duration of this second enrichment phase may be different from that of the first, provided that the saturation threshold previously mentioned is not exceeded.
Le traitement se termine par la trempe sous vide au moyen d'huile ou de gaz surpressé (phase P₅) qui intervient (instant t₅ ) après une phase de diffusion D₂ (instant t₄) d'une durée sensiblement égale à celle de la phase de diffusion D₁.The treatment ends with the vacuum quenching using oil or pressurized gas (phase P₅) which occurs (instant t₅) after a diffusion phase D₂ (instant t₄) of a duration substantially equal to that of the diffusion phase D₁.
Pendant la phase de trempe P₅, la température passe brutalement de la température de traitement à la température ambiante correspondant à l'opération de trempe de l'acier ou de durcissement de l'acier cémenté.During the quenching phase P₅, the temperature suddenly changes from the treatment temperature to the ambient temperature corresponding to the quenching operation of the steel or hardening of the case-hardened steel.
Bien entendu, l'invention ne se limite pas au cycle de traitement précédemment décrit : Ainsi, par exemple, le nombre de phases d'enrichissement et le nombre de phases de diffusion pourraient être supérieurs à deux en fonction de la profondeur cémentée désirée.Of course, the invention is not limited to the previously described treatment cycle: Thus, for example, the number of enrichment phases and the number of diffusion phases could be greater than two depending on the desired cemented depth.
La figure 2 montre une installation apte à effectuer un traitement de cémentation à basse pression utilisant un four de traitement thermique sous vide de type cloche, c'est-à-dire comprenant une enceinte étanche comportant un corps cylindrique 1, axé verticalement et ouvert dans sa partie inférieure, ce corps étant mobile et monté de façon étanche et déconnectable sur une base circulaire 2 formant la sole du four sur laquelle sont posées les pièces à traiter.FIG. 2 shows an installation capable of carrying out a cementation treatment at low pressure using a vacuum type heat treatment furnace of the bell type, that is to say comprising a sealed enclosure comprising a
Le corps 1 renferme un moufle cylindrique 3 en matériau réfractaire, à l'intérieur duquel sont disposées des résistances chauffantes électriques 4 permettant d'assurer un chauffage des pièces par rayonnement.The
Le volume intérieur du four est connecté à un circuit d'aspiration comprenant une pompe à vide 5 pilotée par un circuit de régulation au moins partiellement logé dans une armoire de commande 6.The interior volume of the oven is connected to a suction circuit comprising a
Cette armoire de commande 6 renferme, par ailleurs, les instruments électroniques usuels tels que des afficheurs ou des enregistreurs ainsi que le dispositif de programmation et de régulation du chauffage.This
Par ailleurs, le volume intérieur de l'enceinte est raccordé à un système d'injection de gaz de traitement comprenant une ou plusieurs (ici, une source de propane et une source d'azote) sources de gaz G₁, G₂ reliées à des buses d'injection 7 qui traversent l'ensemble corps 1/moufle 3, par l'intermédiaire d'un circuit comportant successivement un débit-mètre 8 et des électrovannes (bloc 9) associées chacune à une ou plusieurs buses d'injection 7.Furthermore, the interior volume of the enclosure is connected to a treatment gas injection system comprising one or more (here, a source of propane and a source of nitrogen) gas sources G₁, G₂ connected to
Dans cet exemple, le four comprend six groupes de trois buses (B₁ à B₁₈) disposées verticalement les unes au-dessus des autres, ces groupes étant décalés angulairement de 60° les uns par rapport aux autres (figures 3 et 4).In this example, the oven comprises six groups of three nozzles (B₁ to B₁₈) arranged vertically one above the other, these groups being angularly offset by 60 ° with respect to each other (Figures 3 and 4).
La figure 6 est une vue déroulée de la surface cylindrique du moufle 3, dans laquelle on a indiqué les emplacements des buses d'injection B₁ à B₁₈, tandis que la figure 5 montre un mode d'exécution d'un circuit d'injection comprenant neuf électrovannes E₁ à E₉, à raison d'une électrovanne pour deux buses d'injection appartenant chacune à deux groupes différents.FIG. 6 is an unrolled view of the cylindrical surface of the
Le pilotage de l'ouverture et de la fermeture de ces électrovannes est réalisé par un micro-ordinateur 11 convenablement programmé de manière à obtenir, au cours des phases d'enrichissement, un courant de gaz cémentant pulsé en mouvement permanent.The opening and closing of these solenoid valves is controlled by a
En effectuant une séquence d'ouverture/fermeture des électrovannes associées aux buses d'injection représentées sur la figure 6 dans l'ordre suivant (1, 9, 17 - 2, 10, 18 - 3, 11, 13 - 4, 12, 14 - 15, 7, 5 - 16, 8, 6), on obtient une hélice montante et descendante. Avantageusement, chaque électrovanne pourra travailler pendant 2,77 centièmes de seconde pendant une boucle de durée de l'ordre de 0,5 seconde. Le gaz cémentant pourra, quant à lui, avoir à la sortie des buses d'injection une vitesse de 1,48 m/s.By carrying out an opening / closing sequence of the solenoid valves associated with the injection nozzles shown in FIG. 6 in the following order (1, 9, 17 - 2, 10, 18 - 3, 11, 13 - 4, 12, 14 - 15, 7, 5 - 16, 8, 6), a rising and falling propeller is obtained. Advantageously, each solenoid valve can work for 2.77 hundredths of a second during a loop of duration of the order of 0.5 seconds. The cementing gas may, as for it has a speed of 1.48 m / s at the outlet of the injection nozzles.
Par ailleurs, deux électrovannes supplémentaires E₁₀ et E₁₁ sont prévues à la sortie des deux sources G₁, G₂ de manière à envoyer dans le circuit d'injection, soit le gaz cémentant (propane), soit le gaz neutre (azote) utilisé pour nettoyer les buses après chaque phase de cémentation.Furthermore, two additional solenoid valves E₁₀ and E₁₁ are provided at the outlet of the two sources G₁, G₂ so as to send into the injection circuit either the cementing gas (propane) or the neutral gas (nitrogen) used to clean the nozzles after each carburizing phase.
Comme précédemment mentionné, la figure 7 montre un mode d'implantation des buses d'injection dans un four dont on a simplement représenté schématiquement le moufle 12, de forme parallélépipédique.As previously mentioned, FIG. 7 shows a mode of implantation of the injection nozzles in an oven of which the
Dans cet exemple, les faces latérales droite et gauche FD, FG du moufle 12 sont traversées par trois batteries de cinq buses d'injection alignées horizontalement sur trois niveaux respectifs, chaque buse étant indiquée par un point.In this example, the right and left lateral faces FD, FG of the
La face supérieure FS du moufle 12 est, quant à elle, traversée par trois batteries de cinq buses d'injection axées parallèlement aux batteries des faces latérales.The upper face FS of the
Sur la figure 8, les buses de chacune de ces faces sont numérotées de +1 à +18 dans l'ordre de leur ouverture, au cours d'un cycle d'injection, étant entendu que l'électrovanne qui porte le même numéro sur chacune des trois faces du four, s'ouvre en même temps et que la séquence se déroule par ordre croissant des numéros. La vitesse d'injection du gaz en sortie des buses peut être, ici, de l'ordre de 4,71 m/s.In FIG. 8, the nozzles of each of these faces are numbered from +1 to +18 in the order of their opening, during an injection cycle, it being understood that the solenoid valve which has the same number on each of the three faces of the oven opens at the same time and the sequence takes place in ascending order of the numbers. The gas injection speed at the outlet of the nozzles can be, here, of the order of 4.71 m / s.
Grâce à cette disposition, on obtient à l'intérieur du moufle une hélice de gaz horizontale à chaque cycle d'ouverture/fermeture des électrovannes.Thanks to this arrangement, a horizontal gas propeller is obtained inside the muffle at each opening / closing cycle of the solenoid valves.
A titre d'exemple, dans un four cloche du type de celui décrit sur la figure 2, le traitement sur un rond de diamètre 40 mm, d'épaisseur 12 mm, un acier de type 16 MC 5, peut s'effectuer dans les conditions suivantes :
- température sur pièce = 960°C,
- débit de propane = 5 l/mn,
- temps total d'injection de propane = 423 s,
- pression = 3,7 mbar.
- room temperature = 960 ° C,
- propane flow = 5 l / min,
- total propane injection time = 423 s,
- pressure = 3.7 mbar.
Les résultats suivants ont été obtenus :
- profondeur conventionnelle cémentée = 5/10ème de millimètre,
- dureté superficielle (HV 0,1) = 690 à 724 HV,
- % carbone superficiel = 0,75 %,
- flux carbone (mg/h/cm) = 15,
- grosseur de grain = 7-8.
- conventional cemented depth = 5 / 10th of a millimeter,
- surface hardness (HV 0.1) = 690 to 724 HV,
- % surface carbon = 0.75%,
- carbon flux (mg / h / cm) = 15,
- grain size = 7-8.
Claims (8)
- A method for carburizing steel parts, said method consisting in bringing the parts to be processed to a temperature included between 800°C and 1100°C, preferably above 900°C, in a gaseous atmosphere devoid of oxygen, maintained by pumping at a low pressure, and in proceeding with a plurality of successive carbon enrichment phases (C₁, C₂) each obtained by an injection of limited duration of a processing gas comprising one or more pure hydrocarbons, each enrichment phase (C₁, C₂) having a duration lower than the time of passage into the saturation phase of the austenite phase of steel raised to a high temperature, said enrichment phases (C₁, C₂) being separated by diffusion phases under vacuum (D₁, D₂) of greater duration enabling the superficial carbon content to be adjusted, characterized in that said pressure is maintained at a value included between 1 and 10 mbars with a gas flow such that the carburizing atmosphere is saturated or has a high carburizing potential, and in that the processing gas injection phases are obtained by means of a plurality of injection nozzles working according to a sequence enabling a flow of gas in motion to be generated on said parts to be processed.
- The method as claimed in claim 1, characterized in that the gas injected is propane or methane, of which the cracking or dissociation produces ethylene and methane as well as the principal carburizing agent, i.e. atomic carbon, by creating a carbon-saturated atmosphere by means of a suitable initial gas flow.
- The method as claimed in any one of the previous claims, characterized in that the injecting is performed in such a way as to rotate the gas flow around the batch to be processed.
- The device as claimed in claim 1,
characterized in that the duration of each injection phase is included between 1 s and 5 mn and in that the duration of said diffusion phases is always greater than the preceding injection time of carburizing gas. - A device for implementing the method as claimed in any one of the previous claims, said device using a tempering vacuum furnace, comprising, inside an airtight box (1, 2) connected to a pumping unit (5), a thermally insulated muffle (3) equipped with heating means (4), inside which are disposed the batches to be processed, and a plurality of means (G₁, G₂, 7, 8, 9) enabling a processing gas to be injected into said furnace, said pumping (5) unit being designed so that a pressure of the order of 1 to 10 mbars can be obtained inside said box, and said heating means (4) being designed to bring the batch disposed inside said furnace to a temperature included between 800°C and 1,100°C, characterized in that said injecting means (G₁, G₂, 7, 8, 9) comprise a plurality of injection nozzles (7) connected to respective electrovalves (9) controlled by a computer (11) programmed so as to carry out injection phases, each of a duration calculated so as to be loxwer than the time for reaching the saturation phase of the austenite phase of the steel brought to a high temperature, each injection phase comprising a sequence of successive openings and closings of the electrovalves (9) according to a preestablished sequence causing a displacement of the processing gas flow onto the parts to be processed
- The device as claimed in claim 5, characterized in that each injection phase is carried out by means of a plurality of injection nozzles (7) of which the flow is controlled by electrovalves, (9) the layout of the nozzles inside the furnace and the controll the electrovalves (9) by the computer (11) being designed so as to obtain a rotating movement of the gas flow around the batch.
- The device as claimed in claim 6, characterized in that the movement of the gas flow is a rising and falling helix.
- The device as claimed in claim 6, characterized in that the movement of the gas flow is a horizontal helix.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR919111304A FR2681332B1 (en) | 1991-09-13 | 1991-09-13 | METHOD AND DEVICE FOR CEMENTING STEEL IN A LOW PRESSURE ATMOSPHERE. |
| FR9111304 | 1991-09-13 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0532386A1 EP0532386A1 (en) | 1993-03-17 |
| EP0532386B1 true EP0532386B1 (en) | 1996-04-17 |
Family
ID=9416913
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP92402395A Expired - Lifetime EP0532386B1 (en) | 1991-09-13 | 1992-09-03 | Process and apparatus for carburizing steel in an atmosphere of low pressure |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0532386B1 (en) |
| JP (1) | JPH05195192A (en) |
| AT (1) | ATE136946T1 (en) |
| DE (1) | DE69209947D1 (en) |
| FR (1) | FR2681332B1 (en) |
| TW (1) | TW225558B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6093303A (en) * | 1998-08-12 | 2000-07-25 | Swagelok Company | Low temperature case hardening processes |
| US6165597A (en) * | 1998-08-12 | 2000-12-26 | Swagelok Company | Selective case hardening processes at low temperature |
| US9212416B2 (en) | 2009-08-07 | 2015-12-15 | Swagelok Company | Low temperature carburization under soft vacuum |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3460075B2 (en) * | 1995-12-28 | 2003-10-27 | 同和鉱業株式会社 | Metal carburizing method |
| AT404029B (en) * | 1996-09-16 | 1998-07-27 | Ald Aichelin Ges M B H | LOW-PRESSURE REARING PLANT |
| JP2000336469A (en) * | 1999-05-28 | 2000-12-05 | Nachi Fujikoshi Corp | Vacuum carburizing method and device |
| US6547888B1 (en) | 2000-01-28 | 2003-04-15 | Swagelok Company | Modified low temperature case hardening processes |
| FR2813892B1 (en) * | 2000-09-13 | 2003-09-26 | Peugeot Citroen Automobiles Sa | PROCESS FOR THE HEAT TREATMENT OF HYPOEUTECTOID TOOL STEELS |
| FR2821362B1 (en) * | 2001-02-23 | 2003-06-13 | Etudes Const Mecaniques | LOW PRESSURE CEMENTING PROCESS |
| FR2832735B1 (en) * | 2001-11-24 | 2006-06-23 | Bosch Gmbh Robert | DEVICE AND METHOD FOR DEPRESSION CEMENTATION |
| DE10209382B4 (en) * | 2002-03-02 | 2011-04-07 | Robert Bosch Gmbh | Method of carburizing components |
| DE10254846B4 (en) * | 2002-11-25 | 2011-06-16 | Robert Bosch Gmbh | Method for case-hardening components made of hot-work steels by means of vacuum carburizing |
| JP4255815B2 (en) * | 2003-11-28 | 2009-04-15 | 光洋サーモシステム株式会社 | Gas carburizing method |
| JP4587719B2 (en) * | 2004-07-07 | 2010-11-24 | 中外炉工業株式会社 | Carburizing gas production equipment |
| JP5577573B2 (en) * | 2008-08-29 | 2014-08-27 | 株式会社Ｉｈｉ | Vacuum carburizing method and vacuum carburizing apparatus |
| DE102009008664A1 (en) * | 2009-02-12 | 2010-08-19 | Linde Aktiengesellschaft | Apparatus and method for carburizing steel |
| JP6257527B2 (en) | 2012-01-20 | 2018-01-10 | スウエイジロク・カンパニー | Simultaneous flow of activated gas in low-temperature carburizing. |
| US10697054B2 (en) * | 2015-10-30 | 2020-06-30 | Korea Institute Of Industrial Technology | Low temperature carburizing method and carburizing apparatus |
| KR101866754B1 (en) * | 2016-10-31 | 2018-06-18 | 한국생산기술연구원 | Carburizing Method in Low-Pressure Range |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2154398A (en) * | 1936-12-09 | 1939-04-11 | Rca Corp | Frequency modulation receiver |
| FR926776A (en) * | 1945-02-05 | 1947-10-10 | Wildbarfield Electric Furnaces | Heat treatment process and furnace for the implementation of this process |
| US3796615A (en) * | 1971-06-23 | 1974-03-12 | Hayes Inc C I | Method of vacuum carburizing |
| GB1510481A (en) * | 1976-04-02 | 1978-05-10 | British Steel Corp | Carburising coiled strip |
| JPS5354136A (en) * | 1976-10-28 | 1978-05-17 | Ishikawajima Harima Heavy Ind | Vacuum carburizing furnace |
| US4160680A (en) * | 1976-11-05 | 1979-07-10 | Sola Basic Industries, Inc. | Vacuum carburizing |
| GB1559690A (en) * | 1976-11-10 | 1980-01-23 | British Steel Corp | Treatment of steel products |
| JPS5431976A (en) * | 1977-08-13 | 1979-03-09 | Norichika Tanaka | Multiistage vertical incinerator |
| DE3038078A1 (en) * | 1980-10-08 | 1982-05-06 | Linde Ag, 6200 Wiesbaden | METHOD AND DEVICE FOR CARBONING METAL WORKPIECES |
| DE3146042A1 (en) * | 1981-11-20 | 1983-05-26 | Linde Ag, 6200 Wiesbaden | METHOD FOR USEFUL METAL WORKPIECES |
| JPH01212748A (en) * | 1988-02-18 | 1989-08-25 | Daido Steel Co Ltd | Rapid carburizing treatment for steel |
| JPH0222451A (en) * | 1988-07-09 | 1990-01-25 | Michio Sugiyama | Vacuum carburizing method |
-
1991
- 1991-09-13 FR FR919111304A patent/FR2681332B1/en not_active Expired - Lifetime
-
1992
- 1992-09-03 EP EP92402395A patent/EP0532386B1/en not_active Expired - Lifetime
- 1992-09-03 AT AT92402395T patent/ATE136946T1/en not_active IP Right Cessation
- 1992-09-03 DE DE69209947T patent/DE69209947D1/en not_active Expired - Lifetime
- 1992-09-14 JP JP4245041A patent/JPH05195192A/en active Pending
- 1992-10-01 TW TW081107828A patent/TW225558B/zh active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6093303A (en) * | 1998-08-12 | 2000-07-25 | Swagelok Company | Low temperature case hardening processes |
| US6165597A (en) * | 1998-08-12 | 2000-12-26 | Swagelok Company | Selective case hardening processes at low temperature |
| US9212416B2 (en) | 2009-08-07 | 2015-12-15 | Swagelok Company | Low temperature carburization under soft vacuum |
Also Published As
| Publication number | Publication date |
|---|---|
| TW225558B (en) | 1994-06-21 |
| ATE136946T1 (en) | 1996-05-15 |
| EP0532386A1 (en) | 1993-03-17 |
| FR2681332B1 (en) | 1994-06-10 |
| JPH05195192A (en) | 1993-08-03 |
| DE69209947D1 (en) | 1996-05-23 |
| FR2681332A1 (en) | 1993-03-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0532386B1 (en) | Process and apparatus for carburizing steel in an atmosphere of low pressure | |
| Edenhofer et al. | Carburizing of steels | |
| CA2046052C (en) | Method and apparatus for low pressure case-hardening of metal alloy parts | |
| EP3218530B1 (en) | Method and facility for carbonitriding one or more steel parts under low pressure and at a high temperature | |
| EP0096602B1 (en) | Method of heat treating metallic parts by carburization | |
| EP0010484B1 (en) | Improvement in the chromising of steel in the gaseous phase | |
| FR2499592A1 (en) | PROCESS FOR MAKING PROTECTIVE OXIDE LAYERS | |
| CA2280405A1 (en) | Metal strip galvanization process | |
| EP1280943B1 (en) | Low-pressure carburising method | |
| EP0707661B1 (en) | Method of low pressure nitriding a metal workpiece and oven for carrying out said method | |
| EP2732066B1 (en) | Method for cooling metalic articles having been subjected to a nitriding or carbonitriding treatment in a molten salt bath, apparatus therefor and corresponding treated articles | |
| EP1404882B1 (en) | Method for quenching steel in pressurized air | |
| EP0885980B1 (en) | Process for forming a superficial layer having a high hardness by plasma-free thermochemical treatment | |
| EP0067098A1 (en) | Method of ionitriding a steel article which has been plastically deformed in advance | |
| FR2991341A1 (en) | Thermo chemically treating component part of gear box by performing thermo chemical enrichment on set of parts of steel, and performing induction hardening on each of pieces, where enrichment includes cementation enrichment of carbon steel | |
| FR2719057A1 (en) | Method of nitriding metallic surfaces | |
| FR2994195A1 (en) | Thermochemical treatment of steel mechanical parts such as gear box of an automobile, comprises carrying out thermochemical enrichment of carbon steel in a nitrogen line and then structural refining and quenching | |
| JPS62176667A (en) | Vacuum exhausting method | |
| FR2999607A1 (en) | Processing steel parts, comprises refining grain of steel, carrying out thermochemical treatment, heating steel at first temperature higher than transformation finish temperature of austenitic steel, and cooling steel to second temperature | |
| Ivanov et al. | Steel 45 surface modification by a combined electron-ion-plasma method | |
| FR2725015A1 (en) | Low pressure nitriding of metal workpiece | |
| Edenhofer et al. | 3 Vacuum Heat Processing | |
| Jones et al. | Copper Evaporation During Low Pressure Carburizing | |
| RU148230U1 (en) | INSTALLATION FOR NITRATION OF STEEL PRODUCTS | |
| FR2999609A1 (en) | Thermochemically treating steel part i.e. gear train that is used in gear box, comprises performing first thermochemical enrichment process in steel with carbon and a second thermochemical enrichment process in steel with nitrogen |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| 17P | Request for examination filed |
Effective date: 19920914 |
|
| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT CH DE ES GB IT LI NL |
|
| 17Q | First examination report despatched |
Effective date: 19950206 |
|
| GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
| AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AT CH DE ES GB IT LI NL |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 19960417 Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT Effective date: 19960417 Ref country code: GB Effective date: 19960417 Ref country code: ES Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY Effective date: 19960417 Ref country code: AT Effective date: 19960417 |
|
| REF | Corresponds to: |
Ref document number: 136946 Country of ref document: AT Date of ref document: 19960515 Kind code of ref document: T |
|
| REF | Corresponds to: |
Ref document number: 69209947 Country of ref document: DE Date of ref document: 19960523 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19960718 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LI Effective date: 19960930 Ref country code: CH Effective date: 19960930 |
|
| NLV1 | Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act | ||
| GBV | Gb: ep patent (uk) treated as always having been void in accordance with gb section 77(7)/1977 [no translation filed] |
Effective date: 19960417 |
|
| PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
| 26N | No opposition filed | ||
| REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |