EP1844169B1 - Gas quenching cell for steel parts - Google Patents

Gas quenching cell for steel parts Download PDF

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Publication number
EP1844169B1
EP1844169B1 EP06709405.2A EP06709405A EP1844169B1 EP 1844169 B1 EP1844169 B1 EP 1844169B1 EP 06709405 A EP06709405 A EP 06709405A EP 1844169 B1 EP1844169 B1 EP 1844169B1
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Prior art keywords
speed
quenching
plateau
gas
load
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EP06709405.2A
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German (de)
French (fr)
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EP1844169A1 (en
Inventor
Aymeric Goldsteinas
Jean Berlier
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Etudes et Constructions Mecaniques SA
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Etudes et Constructions Mecaniques SA
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/62—Quenching devices
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/613—Gases; Liquefied or solidified normally gaseous material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
    • 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
    • C21D2241/00—Treatments in a special environment
    • C21D2241/01—Treatments in a special environment under pressure
    • 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
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like

Definitions

  • the present invention relates to a gas quenching cell for steel parts and more particularly to a method of gas quenching of steel parts used in such a quenching cell.
  • Methods of gas quenching of steel parts have many advantages over liquid quenching processes, including the fact that treated parts come out dry and clean.
  • Gaseous quenching of steel parts which have previously undergone a heat treatment (heating before quenching, annealing, tempering, etc.) or thermochemical treatment (carburizing, carbonitriding, etc.) is generally carried out with a pressurized gas, generally between 4 and 20 bars.
  • the quenching gas is, for example, nitrogen, argon, helium, carbon dioxide or a mixture of these gases.
  • a quenching operation involves rapidly cooling steel parts which are generally at temperatures between 750 ° C and 1000 ° C. At such temperatures, the steel is essentially in the form of austenite which is stable only at elevated temperatures.
  • An operation of quenching allows by rapid cooling to obtain a transformation from austenite to martensite which has high hardness properties.
  • the quenching operation must be relatively fast so that all the austenite is transformed into martensite without formation of other phases of pearlite or bainite type steel which have properties of hardness lower than martensite.
  • a quenching cell generally comprises at least one motor, generally of the electric type, rotating a stirring element, for example a helix, adapted to circulate the quenching gas in the quenching cell.
  • the quenching gas is usually circulated at the level of the pieces to be cooled at the highest possible rate during the entire quenching operation.
  • the present invention aims to obtain a quenching process of steel parts and a quenching cell for the implementation of such a method for obtaining quenched parts with improved fatigue strength and / or reduced deformations.
  • Another object of the present invention is to obtain a quenching cell for carrying out the quenching process according to the invention and whose structure is little modified compared to a conventional quenching cell.
  • the present invention provides a method of quenching a steel charge by flowing a gas at the charge through a gas drive means, the gas, after being discharged at the charge, being cooled by an exchanger in which circulates a cooling fluid.
  • the drive means is controlled to flow the gas at the load at a speed which varies according to a velocity profile of which at least a portion comprises, successively, a first bearing a first speed, a second bearing a second speed lower than the first speed and a third bearing at the first speed, the transition between the first bearing at the first speed and the second bearing at the second speed being carried out during a rising phase of the fluid temperature. cooling.
  • the static pressure of the gas at the load is decreased during the second bearing at the second speed with respect to the first bearing at the first speed.
  • the drive means is controlled to flow the gas at the first bearing load at the first speed at the second bearing at the second speed when the coolant temperature exceeds a given threshold temperature.
  • the drive means is controlled to flow the gas at the second bearing load at the second speed at the third bearing at the first speed when the coolant temperature decreases below a given additional threshold temperature.
  • the drive means is controlled to flow the gas at the first bearing load at the first speed at the second bearing at the second speed after a specified time.
  • the driving means is controlled to flow the gas at the level of the charge of the fourth bearing at the third speed at the first step at the first speed after a determined duration.
  • the Figures 1A and 1B schematically represent a side sectional view and a front sectional view of a gas quenching cell that can be used according to the invention.
  • the cell comprises an enclosure 10 of generally cylindrical or parallelepipedal shape with a horizontal axis.
  • the cell is closed at one end while the other end comprises a guillotine door system 12 giving access to the cell to introduce or extract a load to be treated 14.
  • the door 12 can close the quenching cell tightly.
  • the load 14 is maintained substantially in the center of the cell on a plate 16.
  • the upper part of the cell is provided with two external motors vertical axis 18, arranged next to each other in the longitudinal direction of the cell. These motors drive respective brewing elements within the cell.
  • the motors 18 are electric motors.
  • the cell is provided with an exchanger 22 disposed on either side of the load 14 in a horizontal plane.
  • the exchanger 22 comprises a circulation duct for a cooling fluid and is adapted to cool the quenching gas passing therethrough.
  • guide plates 24 which join the stirring devices 20 so as to direct the flow of gas produced by the latter between the load 14 and the exchanger 22.
  • the quenching gas s flows, for example down through the charge 14 and up through the exchanger 22.
  • the stirring elements 20 are turbines or fans.
  • the quenching gas is, for example, nitrogen or a mixture of carbon dioxide and helium.
  • the present invention consists in modifying in a controlled manner the flow rate of the quenching gas at the level of the charge 14 during a quenching operation.
  • the quenching cell 18 is equipped with a speed variation system.
  • the speed variation can be obtained via a frequency converter for electric motors.
  • the motors 18 are hydraulic motors, it is possible to provide a system for varying the flow rate of the oil supplying the engines 18.
  • the figure 2 illustrates the principle underlying the choice of the temperature of the cooling fluid at the outlet of the exchanger 22 as a characteristic parameter for varying the flow rate of the quenching gas.
  • the figure 2 represents a classic example of curve 26 of evolution of the the quenching gas velocity at the level of the charge 14, in which the flow rate of the quenching gas is constant and corresponds to the maximum of the capacities of the engines 18.
  • figure 2 also represents a curve 30 of evolution of the temperature of the cooling fluid at the outlet of the exchanger 22 obtained for such a velocity profile.
  • Curve 30 comprises an ascending portion 32 that bends at a peak 34 and is followed by a downward portion 36.
  • the Applicant has demonstrated that the austenite-martensite transformation of the steel constituting the load 14 occurs substantially at the level of the crown 34 of the curve 30.
  • the Applicant has shown that an improvement in the fatigue strength can be obtained by limiting the temperature variations of the charge 14 during the austenite-martensite transformation so as to allow the austenite-martensite transition to take place at relatively homogeneous charging temperatures.
  • the transition from the first maximum speed stage 42 to the intermediate speed stage 44 is carried out when the temperature of the cooling fluid reaches a first given threshold temperature, which corresponds to a temperature slightly lower than the temperature at the summit 34 of the curve 30. It is therefore substantially the temperature of the cooling fluid for which the austenite-martensite transformation of the load 14 begins.
  • the transition from the intermediate speed bearing 44 to the second maximum speed stage 46 is effected when the temperature of the coolant towards the end of the low variation portion 50 decreases below a given second threshold temperature, for example equal to the first given threshold temperature, and which is representative of the fact that the austenite-martensite transformation of the charge 14 is complete.
  • the austenite-martensite transformation of the charge 14 is then performed in its entirety for a flow rate of the quenching gas that is lower than the maximum speed.
  • the intermediate speed is adjusted to a value such that the thermal power recovered by the exchanger 22 corresponds to the thermal power released by the load 14 during the austenite-martensite conversion which is an exothermic reaction.
  • the temperature of the filler 14 is then maintained at a substantially constant and homogeneous temperature during the entire austenite-martensite transformation. 14.
  • the intermediate speed is adapted to obtain the temperature of the coolant as constant as possible during the portion 50.
  • the static pressure of the quenching gas can be maintained at a constant value throughout the quenching operation between 4 and 20 bar.
  • the static pressure of the quenching gas in the quenching cell is reduced during the application of the intermediate speed bearing in a range from 30% to 80% of the static pressure of the quench gas. quenching during the first and second maximum speed stages. This makes it possible to control, in combination with the intermediate speed of the quenching gas, the thermal power taken from the charge 14 during the austenite-martensite transformation.
  • the figure 4 represents two curves 54, 56 of temperature evolution measured at the level of the load 14 during a quenching operation of the load 14 respectively for a conventional quenching process during which the flow rate of the quenching gas remains constant and maximum and the first example of quenching process according to the invention. More precisely, the curve 56 has been obtained in the case where the duration T1 of application of the first maximum speed stage 42 is 50 seconds and the duration T2 of the intermediate speed stage 44 is 310 seconds. The intermediate speed corresponds in this example to 30% of the maximum speed.
  • the static pressure of the quenching gas which in this example is nitrogen, is 16 bar during the first and second maximum speed stages 42, 46 and 2 bar during the intermediate speed bearing 44. note that after 50 seconds, the curve 56 decreases significantly less than the curve 54.
  • the variation in the temperature of the load 14 is limited during the austenite-martensite transformation.
  • the Applicant has demonstrated an improvement in the fatigue strength of the parts constituting the quenched load 14 according to the first example of quenching process of the invention.
  • One explanation would be that since the austenite-martensite transformation is carried out at temperatures whose variations are limited, fewer internal mechanical stresses appear in the load 14, which results in an improvement in the fatigue strength.
  • the first and second threshold temperatures depend on many parameters, including the type of steel constituting the charge 14 and the area of the exchange surface between the charge 14 and the quenching gas.
  • the determination of the first and second threshold temperatures can be performed by quenching the charge 14 with a maximum gas flow rate so as to determine the curve shown in FIG. figure 2 14.
  • the first and second threshold temperatures then correspond to a given percentage of the maximum temperature of the curve 30. It is then possible for the same type of charge to implement the first example of the process of the present invention.
  • the passages of the first maximum speed bearing 42 to the intermediate speed bearing 44 and the intermediate speed bearing 44 to the second maximum speed stage 46 are respectively performed when the temperature of the coolant exceeds the first threshold temperature and decreases below the second threshold temperature.
  • the time T1 necessary for the temperature of the coolant to reach the first threshold temperature can be determined. It is not then necessary, in normal operation, to provide a temperature sensor at the exchanger 22, the passage of the first maximum speed bearing 42 to the intermediate speed bearing 44 being automatically achieved at the end of the period T1 .
  • the transition from the intermediate speed bearing 44 to the second maximum speed stage 46 can then be automatically performed after the duration T2, determined, for example, empirically.
  • the intermediate speed bearing 44 is maintained even after the temperature of the cooling fluid decreases below the second given threshold temperature, as defined above, towards the end of the weak portion. Variations 50.
  • the passage of the intermediate speed bearing 44 to the second level of maximum speed 46 is then performed only after the lapse of a duration greater than the duration T 2 as defined above.
  • the curve 42 comprises, after the portion of small variations 50, a downward portion whose slope is, in absolute value, lower than the slope of the downward portion 52 represented in FIG. figure 3 and which is prolonged by an additional portion of small variations.
  • the second embodiment of the quenching process of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 corresponds successively to a first intermediate speed stage 62 for a period of time. T1 'and at a maximum speed level 64 until the end of the quenching operation.
  • the motors 18 are controlled so that the flow rate of the quenching gas varies between 0% and 70% of the maximum speed.
  • the curve 60 of evolution of the temperature of the cooling fluid comprises an upward portion 66 less marked than the upward portion 32 of the curve 30. The temperature of the cooling fluid therefore increases less rapidly than in the case where the quenching speed is maximum.
  • the ascending portion 66 continues to a vertex 68 and is extended by a downward portion 70.
  • the duration T1 'can extend from 5 to 30 seconds depending on the total duration of the operation quenching. In addition, the duration T1 'can be determined empirically.
  • the cooling rate of the charge 14 is lower than that which would result from a maximum flow rate of the quenching gas. Cooling being slower, the deformations of the load 14 are less important.
  • the mechanical inertia of the load 14 has increased. Such an increase in the mechanical inertia limits the subsequent deformations of the load 14 when the flow rate of the quenching gas is subsequently increased.
  • the local deformations of the charge 14, during the quenching operation are thus reduced overall since the cooling of the charge 14 with the flow rate of the maximum quenching gas is performed when the charge has already acquired a mechanical inertia. sufficient and therefore opposes a higher resistance to deformations.
  • the figure 6 represents a curve 72 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for the third example of quenching process according to the invention and a curve 74 representative of the evolution of the temperature of the quenching gas.
  • exchanger cooling fluid 22 obtained with such a quenching gas velocity profile.
  • the curve 30 of evolution of the temperature of the cooling fluid for a quench gas circulating at maximum speed during the entire quenching operation has been reproduced in dotted lines.
  • the third embodiment of the quenching process of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 successively corresponds to an intermediate speed bearing 76 during a period T1 ", a maximum speed bearing 78 for a duration T2", an intermediate speed bearing 80 for a duration T3 "and a maximum speed bearing 82 until the end of the quenching operation.
  • the motors 18 are controlled so that the flow velocity quenching gas varies between 0% and 70% of the maximum speed and during the intermediate speed stage 80, the flow rate of the quenching gas varies between 40% and 70% of the maximum speed.
  • the curve 74 for changing the temperature of the cooling fluid comprises an upward portion 84 less marked than the upward portion 32 of the curve 30.
  • the curve 74 comprises an ascending portion 86 at the intermediate speed bearing 80, the curve 74 comprises a bearing 88 of small variations and at the maximum speed bearing 82, the curve 74 comprises a downward portion 90.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
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Description

Domaine de l'inventionField of the invention

La présente invention concerne une cellule de trempe sous gaz pour pièces en acier et plus particulièrement un procédé de trempe sous gaz de pièces en acier mis en oeuvre dans une telle cellule de trempe.The present invention relates to a gas quenching cell for steel parts and more particularly to a method of gas quenching of steel parts used in such a quenching cell.

Exposé de l'art antérieurPresentation of the prior art

Les procédés de trempe sous gaz de pièces en acier présentent de nombreux intérêts par rapport à des procédés de trempe par liquide, notamment le fait que les pièces traitées sortent sèches et propres.Methods of gas quenching of steel parts have many advantages over liquid quenching processes, including the fact that treated parts come out dry and clean.

La trempe gazeuse de pièces en acier ayant subi au préalable un traitement thermique (chauffage avant trempe, recuit, revenu...) ou thermochimique (cémentation, carbonitruration...) est généralement réalisée avec un gaz sous pression, de façon générale entre 4 et 20 bars. Le gaz de trempe est par exemple de l'azote, de l'argon, de l'hélium, du dioxyde de carbone ou un mélange de ces gaz.Gaseous quenching of steel parts which have previously undergone a heat treatment (heating before quenching, annealing, tempering, etc.) or thermochemical treatment (carburizing, carbonitriding, etc.) is generally carried out with a pressurized gas, generally between 4 and 20 bars. The quenching gas is, for example, nitrogen, argon, helium, carbon dioxide or a mixture of these gases.

Une opération de trempe consiste à refroidir de façon rapide des pièces en acier qui sont généralement à des températures comprises entre 750°C et 1000°C. A de telles températures, l'acier se trouve essentiellement sous la forme d'austénite qui n'est stable qu'à des températures élevées. Une opération de trempe permet par un refroidissement rapide d'obtenir une transformation de l'austénite en martensite qui présente des propriétés de dureté élevées. L'opération de trempe doit être relativement rapide pour que la totalité de l'austénite se transforme en martensite sans formation d'autres phases d'acier de type perlite ou bainite qui ont des propriétés de dureté inférieures à la martensite.A quenching operation involves rapidly cooling steel parts which are generally at temperatures between 750 ° C and 1000 ° C. At such temperatures, the steel is essentially in the form of austenite which is stable only at elevated temperatures. An operation of quenching allows by rapid cooling to obtain a transformation from austenite to martensite which has high hardness properties. The quenching operation must be relatively fast so that all the austenite is transformed into martensite without formation of other phases of pearlite or bainite type steel which have properties of hardness lower than martensite.

Une cellule de trempe comprend généralement au moins un moteur, généralement du type électrique, entraînant en rotation un élément de brassage, par exemple une hélice, adapté à mettre en circulation le gaz de trempe dans la cellule de trempe. Pour obtenir un refroidissement rapide des pièces introduites dans la cellule de trempe, on fait habituellement circuler le gaz de trempe au niveau des pièces à refroidir à une vitesse la plus élevée possible pendant la totalité de l'opération de trempe.A quenching cell generally comprises at least one motor, generally of the electric type, rotating a stirring element, for example a helix, adapted to circulate the quenching gas in the quenching cell. In order to obtain rapid cooling of the pieces introduced into the quenching cell, the quenching gas is usually circulated at the level of the pieces to be cooled at the highest possible rate during the entire quenching operation.

Une opération de trempe est donc réalisée classiquement en imposant une pression statique de gaz de trempe dans la cellule de trempe et en commandant le moteur à une vitesse de rotation maximale pour obtenir une vitesse de circulation maximale du gaz de trempe au niveau des pièces en acier à refroidir.A quenching operation is thus conventionally performed by imposing a quenching gas static pressure in the quenching cell and controlling the engine at a maximum rotational speed to obtain a maximum flow rate of the quenching gas at the steel parts. to cool.

Bien que les procédés de trempe au gaz précédemment décrits permettent l'obtention de pièces trempées ayant une tenue en fatigue tout à fait satisfaisante, il serait souhaitable de prévoir un procédé de trempe au gaz permettant d'améliorer encore davantage la tenue en fatigue des pièces trempées.Although the previously described gas-quenching methods make it possible to obtain quenched parts having a completely satisfactory fatigue strength, it would be desirable to provide a gas-quenching method which makes it possible to further improve the fatigue strength of the parts. soaked.

Par ailleurs, bien que les procédés de trempe au gaz précédemment décrits permettent l'obtention de pièces trempées dont les déformations sont fortement diminuées par rapport à des procédés de trempe à l'huile, il serait souhaitable de prévoir un procédé de trempe au gaz permettant de diminuer encore davantage les déformations des pièces trempées.Furthermore, although the previously described gas quenching processes make it possible to obtain quenched parts whose deformations are greatly reduced compared to oil quenching processes, it would be desirable to provide a gas quenching process which makes it possible to obtain quenched parts. to further reduce the deformations of the quenched parts.

Résumé de l'inventionSummary of the invention

La présente invention vise à obtenir un procédé de trempe de pièces en acier et une cellule de trempe pour la mise en oeuvre d'un tel procédé permettant l'obtention de pièces trempées à tenue en fatigue améliorée et/ou à déformations réduites.The present invention aims to obtain a quenching process of steel parts and a quenching cell for the implementation of such a method for obtaining quenched parts with improved fatigue strength and / or reduced deformations.

Un autre objet de la présente invention est d'obtenir une cellule de trempe permettant la mise en oeuvre du procédé de trempe selon l'invention et dont la structure est peu modifiée par rapport à une cellule de trempe classique.Another object of the present invention is to obtain a quenching cell for carrying out the quenching process according to the invention and whose structure is little modified compared to a conventional quenching cell.

Dans ce but, la présente invention prévoit un procédé de trempe d'une charge en acier par écoulement d'un gaz au niveau de la charge par l'intermédiaire d'un moyen d'entraînement du gaz, le gaz, après s'être écoulé au niveau de la charge, étant refroidi par un échangeur dans lequel circule un fluide de refroidissement. Le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge à une vitesse qui varie selon un profil de vitesses dont au moins une partie comprend, successivement, un premier palier une première vitesse, un second palier à une seconde vitesse inférieure à la première vitesse et un troisième palier à la première vitesse, la transition entre le premier palier à la première vitesse et le second palier à la seconde vitesse étant réalisée au cours d'une phase de montée de la température du fluide de refroidissement.For this purpose, the present invention provides a method of quenching a steel charge by flowing a gas at the charge through a gas drive means, the gas, after being discharged at the charge, being cooled by an exchanger in which circulates a cooling fluid. The drive means is controlled to flow the gas at the load at a speed which varies according to a velocity profile of which at least a portion comprises, successively, a first bearing a first speed, a second bearing a second speed lower than the first speed and a third bearing at the first speed, the transition between the first bearing at the first speed and the second bearing at the second speed being carried out during a rising phase of the fluid temperature. cooling.

Selon un mode de réalisation de la présente invention, la pression statique du gaz au niveau de la charge est diminuée pendant le second palier à la seconde vitesse par rapport au premier palier à la première vitesse.According to one embodiment of the present invention, the static pressure of the gas at the load is decreased during the second bearing at the second speed with respect to the first bearing at the first speed.

Selon un mode de réalisation de la présente invention, le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge du premier palier à la première vitesse au second palier à la seconde vitesse lorsque la température du fluide de refroidissement dépasse une température de seuil donnée.According to one embodiment of the present invention, the drive means is controlled to flow the gas at the first bearing load at the first speed at the second bearing at the second speed when the coolant temperature exceeds a given threshold temperature.

Selon un mode de réalisation de la présente invention, le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge du second palier à la seconde vitesse au troisième palier à la première vitesse lorsque la température du fluide de refroidissement diminue en dessous d'une température de seuil supplémentaire donnée.According to one embodiment of the present invention, the drive means is controlled to flow the gas at the second bearing load at the second speed at the third bearing at the first speed when the coolant temperature decreases below a given additional threshold temperature.

Selon un mode de réalisation de la présente invention, le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge du premier palier à la première vitesse au second palier à la seconde vitesse après une durée déterminée.According to one embodiment of the present invention, the drive means is controlled to flow the gas at the first bearing load at the first speed at the second bearing at the second speed after a specified time.

Selon un mode de réalisation de la présente invention, le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge selon un profil de vitesses comprenant, depuis le début d'une opération de trempe, successivement un quatrième palier à une troisième vitesse inférieure à la première vitesse et le premier palier à la première vitesse, la transition entre le quatrième palier à la troisième vitesse et le premier palier à la première vitesse étant réalisée au cours d'une phase de montée de la température du fluide de refroidissement.According to one embodiment of the present invention, the drive means is controlled to flow the gas at the load according to a velocity profile comprising, from the beginning of a quenching operation, successively a fourth bearing at a third speed lower than the first speed and the first bearing at the first speed, the transition between the fourth bearing at the third speed and the first bearing at the first speed being carried out during a phase of raising the temperature of the cooling fluid.

Selon un mode de réalisation de la présente invention, le moyen d'entraînement est commandé pour faire s'écouler le gaz au niveau de la charge du quatrième palier à la troisième vitesse au premier palier à la première vitesse après une durée déterminée.According to one embodiment of the present invention, the driving means is controlled to flow the gas at the level of the charge of the fourth bearing at the third speed at the first step at the first speed after a determined duration.

Brève description des dessinsBrief description of the drawings

Ces objets, caractéristiques et avantages, ainsi que d'autres de la présente invention seront exposés en détail dans la description suivante d'exemples de réalisation particuliers faite à titre non-limitatif en relation avec les figures jointes parmi lesquelles :

  • les figures 1A et 1B représentent deux vues d'un exemple de réalisation d'une cellule de trempe sous gaz selon l'invention ;
  • la figure 2 représente l'évolution de la vitesse du gaz de trempe au niveau d'une charge contenue dans une cellule de trempe selon les figures 1A et 1B et l'évolution de la température du fluide de refroidissement d'un échangeur de la cellule dans le cas d'un procédé classique de trempe ;
  • la figure 3 représente l'évolution de la vitesse du gaz de trempe au niveau d'une charge contenue dans une cellule de trempe selon les figures 1A et 1B et l'évolution de la température du fluide de refroidissement d'un échangeur de la cellule dans le cas d'un premier exemple de procédé de trempe selon l'invention ;
  • la figure 4 représente l'évolution de la température au niveau d'une charge contenue dans une cellule de trempe selon les figures 1A et 1B traitée selon un procédé de trempe classique et le premier exemple de procédé de trempe selon l'invention ;
  • la figure 5 représente l'évolution de la vitesse du gaz de trempe au niveau d'une charge contenue dans une cellule de trempe selon les figures 1A et 1B et l'évolution de la température du fluide de refroidissement d'un échangeur de la cellule dans le cas d'un deuxième exemple de procédé de trempe selon l'invention ; et
  • la figure 6 représente l'évolution de la vitesse du gaz de trempe au niveau d'une charge contenue dans une cellule de trempe selon les figures 1A et 1B et l'évolution de la température du fluide de refroidissement d'un échangeur de la cellule dans le cas d'un troisième exemple de procédé de trempe selon l'invention.
These and other objects, features, and advantages of the present invention will be set forth in detail in the following description of particular embodiments given in a non-limiting manner in relation to the attached figures among which:
  • the Figures 1A and 1B represent two views of an exemplary embodiment of a gas quenching cell according to the invention;
  • the figure 2 represents the evolution of the quenching gas velocity at a charge contained in a quenching cell according to the Figures 1A and 1B and the evolution of the temperature of the cooling fluid of a cell exchanger in the case of a conventional quenching process;
  • the figure 3 represents the evolution of the quenching gas velocity at a charge contained in a quenching cell according to the Figures 1A and 1B and the change in the temperature of the cooling fluid of an exchanger of the cell in the case of a first example of a quenching process according to the invention;
  • the figure 4 represents the evolution of the temperature at the level of a charge contained in a quenching cell according to the Figures 1A and 1B treated according to a conventional quenching process and the first example of quenching process according to the invention;
  • the figure 5 represents the evolution of the quenching gas velocity at a charge contained in a quenching cell according to the Figures 1A and 1B and the change in the temperature of the cooling fluid of an exchanger of the cell in the case of a second example of quenching process according to the invention; and
  • the figure 6 represents the evolution of the quenching gas velocity at a charge contained in a quenching cell according to the Figures 1A and 1B and the change in the temperature of the cooling fluid of an exchanger of the cell in the case of a third example of a quenching process according to the invention.

Description détailléedetailed description

Les figures 1A et 1B représentent schématiquement une vue en coupe latérale et une vue en coupe de face d'une cellule de trempe sous gaz pouvant être utilisée selon l'invention. La cellule comporte une enceinte 10 de forme générale cylindrique ou parallélépipédique à axe horizontal. La cellule est fermée par une extrémité tandis que l'autre extrémité comporte un système de porte guillotine 12 donnant accès à la cellule pour y introduire ou en extraire une charge à traiter 14. Bien entendu, la porte 12 permet de fermer la cellule de trempe de manière étanche. La charge 14 est maintenue sensiblement au centre de la cellule sur un plateau 16.The Figures 1A and 1B schematically represent a side sectional view and a front sectional view of a gas quenching cell that can be used according to the invention. The cell comprises an enclosure 10 of generally cylindrical or parallelepipedal shape with a horizontal axis. The cell is closed at one end while the other end comprises a guillotine door system 12 giving access to the cell to introduce or extract a load to be treated 14. Of course, the door 12 can close the quenching cell tightly. The load 14 is maintained substantially in the center of the cell on a plate 16.

La partie supérieure de la cellule est munie de deux moteurs externes à axe vertical 18, disposés l'un à côté de l'autre dans le sens longitudinal de la cellule. Ces moteurs entraînent des éléments de brassage respectifs 20 à l'intérieur de la cellule. A titre d'exemple, les moteurs 18 sont des moteurs électriques.The upper part of the cell is provided with two external motors vertical axis 18, arranged next to each other in the longitudinal direction of the cell. These motors drive respective brewing elements within the cell. For example, the motors 18 are electric motors.

Comme cela est visible à la figure 1B, la cellule est munie d'un échangeur 22 disposé de part et d'autre de la charge 14 dans un plan horizontal. L'échangeur 22 comprend une conduite de circulation d'un fluide de refroidissement et est adapté à refroidir le gaz de trempe qui le traverse. Entre l'échangeur 22 et la charge 14 sont disposées des tôles de guidage 24 qui rejoignent les dispositifs de brassage 20 de manière à diriger l'écoulement de gaz produit par ces derniers entre la charge 14 et l'échangeur 22. Avec cette configuration, le gaz de trempe s'écoule, par exemple en descendant à travers la charge 14 et en remontant à travers l'échangeur 22. A titre d'exemple, les éléments de brassage 20 sont des turbines ou des ventilateurs. Le gaz de trempe est, par exemple, de l'azote ou un mélange de dioxyde de carbone et d'hélium.As can be seen in Figure 1B , the cell is provided with an exchanger 22 disposed on either side of the load 14 in a horizontal plane. The exchanger 22 comprises a circulation duct for a cooling fluid and is adapted to cool the quenching gas passing therethrough. Between the exchanger 22 and the load 14 is arranged guide plates 24 which join the stirring devices 20 so as to direct the flow of gas produced by the latter between the load 14 and the exchanger 22. With this configuration, the quenching gas s flows, for example down through the charge 14 and up through the exchanger 22. For example, the stirring elements 20 are turbines or fans. The quenching gas is, for example, nitrogen or a mixture of carbon dioxide and helium.

La présente invention consiste à modifier de façon contrôlée la vitesse de circulation du gaz de trempe au niveau de la charge 14 au cours d'une opération de trempe. Pour ce faire, on équipe la cellule de trempe 18 d'un système de variation de vitesses. A titre d'exemple, la variation de vitesse peut être obtenue par l'intermédiaire d'un variateur de fréquence pour des moteurs électriques. Dans le cas où les moteurs 18 sont des moteurs hydrauliques, on peut prévoir un système de variation du débit de l'huile alimentant les moteurs 18.The present invention consists in modifying in a controlled manner the flow rate of the quenching gas at the level of the charge 14 during a quenching operation. To do this, the quenching cell 18 is equipped with a speed variation system. For example, the speed variation can be obtained via a frequency converter for electric motors. In the case where the motors 18 are hydraulic motors, it is possible to provide a system for varying the flow rate of the oil supplying the engines 18.

Selon la présente invention, l'élaboration d'un profil de vitesses du gaz de trempe s'écoulant au niveau de la charge 14 à tremper est obtenue à partir d'un paramètre caractéristique représentatif de la température moyenne au niveau de la charge 14. Le paramètre caractéristique correspond à la température du fluide de refroidissement au niveau de la sortie de l'échangeur 22, c'est-à-dire lorsque la température du fluide de refroidissement circulant dans l'échangeur 22 est la plus élevée. En effet, la courbe représentative de l'évolution de la température du fluide de refroidissement en sortie de l'échangeur 22 est caractéristique de l'énergie retirée à la charge 14.According to the present invention, the development of a velocity profile of the quenching gas flowing at the level of the charge 14 to be quenched is obtained from a characteristic parameter representative of the average temperature at the level of the charge 14. The characteristic parameter corresponds to the temperature of the cooling fluid at the outlet of exchanger 22, that is to say when the temperature of the cooling fluid circulating in exchanger 22 is the highest. Indeed, the curve representative of the evolution of the temperature of the cooling fluid at the outlet of the exchanger 22 is characteristic of the energy removed at the load 14.

La figure 2 illustre le principe sous-jacent au choix de la température du fluide de refroidissement en sortie de l'échangeur 22 comme paramètre caractéristique pour faire varier la vitesse de circulation du gaz de trempe. La figure 2 représente un exemple classique de courbe 26 d'évolution de la vitesse du gaz de trempe au niveau de la charge 14, dans lequel la vitesse d'écoulement du gaz de trempe est constante et correspond au maximum des capacités des moteurs 18. La figure 2 représente également une courbe 30 d'évolution de la température du fluide de refroidissement en sortie de l'échangeur 22 obtenue pour un tel profil de vitesses. La courbe 30 comprend une portion ascendante 32 s'infléchissant au niveau d'un sommet 34 et suivie d'une portion descendante 36.The figure 2 illustrates the principle underlying the choice of the temperature of the cooling fluid at the outlet of the exchanger 22 as a characteristic parameter for varying the flow rate of the quenching gas. The figure 2 represents a classic example of curve 26 of evolution of the the quenching gas velocity at the level of the charge 14, in which the flow rate of the quenching gas is constant and corresponds to the maximum of the capacities of the engines 18. figure 2 also represents a curve 30 of evolution of the temperature of the cooling fluid at the outlet of the exchanger 22 obtained for such a velocity profile. Curve 30 comprises an ascending portion 32 that bends at a peak 34 and is followed by a downward portion 36.

La demanderesse a mis en évidence que la transformation austénite-martensite de l'acier constituant la charge 14 se produit sensiblement au niveau du sommet 34 de la courbe 30. La demanderesse a mis en évidence qu'une amélioration de la tenue en fatigue peut être obtenue en limitant les variations de température de la charge 14 lors de la transformation austénite-martensite de façon à permettre que la transition austénite-martensite se réalise à des températures de charge 14 relativement homogènes.The Applicant has demonstrated that the austenite-martensite transformation of the steel constituting the load 14 occurs substantially at the level of the crown 34 of the curve 30. The Applicant has shown that an improvement in the fatigue strength can be obtained by limiting the temperature variations of the charge 14 during the austenite-martensite transformation so as to allow the austenite-martensite transition to take place at relatively homogeneous charging temperatures.

La figure 3 représente une courbe 40 représentative de l'évolution de la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 pour un premier exemple de procédé de trempe selon l'invention et une courbe 42 représentative de l'évolution de la température du fluide de refroidissement de l'échangeur 22 correspondant à un tel profil de vitesses de gaz de trempe. A titre de comparaison, on a reproduit, en traits pointillés, la courbe 30 d'évolution de la température du fluide de refroidissement pour un gaz de trempe circulant à vitesse maximale pendant la totalité de l'opération de trempe.The figure 3 represents a curve 40 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for a first example of quenching process according to the invention and a curve 42 representative of the evolution of the quenching temperature. exchanger cooling fluid 22 corresponding to such a profile of quenching gas velocities. By way of comparison, the curve 30 of evolution of the temperature of the cooling fluid for a quench gas circulating at maximum speed during the entire quenching operation has been reproduced in dotted lines.

Le premier procédé de trempe selon l'invention consiste à commander les moteurs 18 de sorte que la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 corresponde successivement à un premier palier de vitesse maximale 42 pendant une durée T1, à un palier de vitesse intermédiaire 44 pendant une durée T2 et à un second palier de vitesse maximale 46 jusqu'à la fin de l'opération de trempe. A titre d'exemple, pendant le palier 44, les moteurs 18 sont commandés de sorte que la vitesse d'écoulement du gaz de trempe chute de 30 à 60 % par rapport à la vitesse maximale. Pendant le premier palier 42, la courbe 42 d'évolution de la température du fluide de refroidissement comprend une portion ascendante 48 qui suit sensiblement celle de la courbe 30. Lors du palier de vitesse intermédiaire 44, la température du fluide de refroidissement tend à se stabiliser de sorte que la courbe 40 comprend une portion de faibles variations 50. Lors du second palier de vitesse maximale 46, la courbe 42 suit une portion descendante 52.The first quenching process according to the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 corresponds successively to a first maximum speed level 42 during a duration T1, at a speed of intermediate speed bearing 44 for a duration T2 and a second level of maximum speed 46 until the end of the quenching operation. For example, during stage 44, the motors 18 are controlled so that the flow rate of the quenching gas drops by 30 to 60% with respect to the maximum speed. During the first stage 42, the curve 42 for changing the temperature of the cooling fluid comprises an ascending portion 48 which substantially follows that of the curve 30. During the intermediate speed bearing 44, the temperature of the cooling fluid tends to stabilize so that the curve 40 comprises a portion of small variations 50. At the second maximum speed stage 46, the curve 42 follows a downward portion 52.

Le passage du premier palier de vitesse maximale 42 au palier de vitesse intermédiaire 44 est effectué lorsque la température du fluide de refroidissement atteint une première température de seuil donnée, qui correspond à une température légèrement inférieure à la température au sommet 34 de la courbe 30. Il s'agit donc sensiblement de la température du fluide de refroidissement pour laquelle la transformation austénite-martensite de la charge 14 débute. Le passage du palier de vitesse intermédiaire 44 au second palier de vitesse maximale 46 est effectué lorsque la température du fluide de refroidissement, vers la fin de la portion de faibles variations 50, diminue en deçà d'une seconde température de seuil donnée, par exemple égale à la première température de seuil donnée, et qui est représentative du fait que la transformation austénite-martensite de la charge 14 est achevée.The transition from the first maximum speed stage 42 to the intermediate speed stage 44 is carried out when the temperature of the cooling fluid reaches a first given threshold temperature, which corresponds to a temperature slightly lower than the temperature at the summit 34 of the curve 30. It is therefore substantially the temperature of the cooling fluid for which the austenite-martensite transformation of the load 14 begins. The transition from the intermediate speed bearing 44 to the second maximum speed stage 46 is effected when the temperature of the coolant towards the end of the low variation portion 50 decreases below a given second threshold temperature, for example equal to the first given threshold temperature, and which is representative of the fact that the austenite-martensite transformation of the charge 14 is complete.

La transformation austénite-martensite de la charge 14 est alors réalisée en totalité pour une vitesse d'écoulement du gaz de trempe inférieure à la vitesse maximale. De façon avantageuse, la vitesse intermédiaire est ajustée à une valeur telle que la puissance thermique récupérée par l'échangeur 22 correspond à la puissance thermique libérée par la charge 14 pendant la transformation austénite-martensite qui est une réaction exothermique. La température de la charge 14 est alors maintenue à une température sensiblement constante et homogène pendant la totalité de la transformation austénite-martensite de l'ensemble de la charge 14. En pratique, la vitesse intermédiaire est adaptée pour obtenir la température du fluide de refroidissement la plus constante possible au cours de la portion 50.The austenite-martensite transformation of the charge 14 is then performed in its entirety for a flow rate of the quenching gas that is lower than the maximum speed. Advantageously, the intermediate speed is adjusted to a value such that the thermal power recovered by the exchanger 22 corresponds to the thermal power released by the load 14 during the austenite-martensite conversion which is an exothermic reaction. The temperature of the filler 14 is then maintained at a substantially constant and homogeneous temperature during the entire austenite-martensite transformation. 14. In practice, the intermediate speed is adapted to obtain the temperature of the coolant as constant as possible during the portion 50.

Dans le premier exemple de réalisation, la pression statique du gaz de trempe peut être maintenue à une valeur constante pendant toute l'opération de trempe entre 4 et 20 bars. Selon une variante du premier exemple de réalisation, la pression statique du gaz de trempe dans la cellule de trempe est diminuée lors de l'application du palier de vitesse intermédiaire dans une plage allant de 30 % à 80 % de la pression statique du gaz de trempe pendant les premier et second paliers de vitesse maximale. Ceci permet de contrôler en combinaison avec la vitesse intermédiaire du gaz de trempe, la puissance thermique prélevée à la charge 14 pendant la transformation austénite-martensite.In the first exemplary embodiment, the static pressure of the quenching gas can be maintained at a constant value throughout the quenching operation between 4 and 20 bar. According to a variant of the first exemplary embodiment, the static pressure of the quenching gas in the quenching cell is reduced during the application of the intermediate speed bearing in a range from 30% to 80% of the static pressure of the quench gas. quenching during the first and second maximum speed stages. This makes it possible to control, in combination with the intermediate speed of the quenching gas, the thermal power taken from the charge 14 during the austenite-martensite transformation.

La figure 4 représente deux courbes 54, 56 d'évolution de la température mesurée au niveau de la charge 14 pendant une opération de trempe de la charge 14 respectivement pour un procédé de trempe classique pendant lequel la vitesse d'écoulement du gaz de trempe demeure constante et maximale et le premier exemple de procédé de trempe selon l'invention. Plus précisément, la courbe 56 a été obtenue dans le cas où la durée T1 d'application du premier palier de vitesse maximale 42 est de 50 secondes et la durée T2 du palier de vitesse intermédiaire 44 est de 310 secondes. La vitesse intermédiaire correspond, dans le présent exemple, à 30 % de la vitesse maximale. La pression statique du gaz de trempe, qui est, dans le présent exemple, de l'azote, est de 16 bars pendant les premier et second paliers de vitesse maximale 42, 46 et de 2 bars pendant le palier de vitesse intermédiaire 44. On notera qu'après 50 secondes, la courbe 56 diminue nettement moins que la courbe 54. La variation de la température de la charge 14 est donc limitée pendant la transformation austénite-martensite.The figure 4 represents two curves 54, 56 of temperature evolution measured at the level of the load 14 during a quenching operation of the load 14 respectively for a conventional quenching process during which the flow rate of the quenching gas remains constant and maximum and the first example of quenching process according to the invention. More precisely, the curve 56 has been obtained in the case where the duration T1 of application of the first maximum speed stage 42 is 50 seconds and the duration T2 of the intermediate speed stage 44 is 310 seconds. The intermediate speed corresponds in this example to 30% of the maximum speed. The static pressure of the quenching gas, which in this example is nitrogen, is 16 bar during the first and second maximum speed stages 42, 46 and 2 bar during the intermediate speed bearing 44. note that after 50 seconds, the curve 56 decreases significantly less than the curve 54. The variation in the temperature of the load 14 is limited during the austenite-martensite transformation.

La demanderesse a mis en évidence une amélioration de la tenue en fatigue des pièces constituant la charge 14 trempée selon le premier exemple de procédé de trempe de l'invention. Une explication serait que la transformation austénite-martensite se faisant à des températures dont les variations sont limitées, il apparaît moins de contraintes mécaniques internes dans la charge 14 d'où il résulte une amélioration de la tenue en fatigue.The Applicant has demonstrated an improvement in the fatigue strength of the parts constituting the quenched load 14 according to the first example of quenching process of the invention. One explanation would be that since the austenite-martensite transformation is carried out at temperatures whose variations are limited, fewer internal mechanical stresses appear in the load 14, which results in an improvement in the fatigue strength.

A titre d'exemple, pour une charge 14 constituée d'un acier du type 27MnCr5 et traitée selon un procédé de cémentation basse pression, la demanderesse a mis en évidence une augmentation de la tenue à la fatigue de l'ordre de 20 % par rapport à une trempe à l'huile froide (huile à 60°C) ou une trempe à l'azote à pression constante (16 bars) et à vitesse d'écoulement maximale du gaz de trempe.For example, for a load 14 consisting of a 27MnCr5 type steel and treated by a low pressure carburizing process, the applicant has demonstrated an increase in the fatigue strength of the order of 20% by compared with a cold oil quench (oil at 60 ° C) or quenching with nitrogen at constant pressure (16 bar) and with a maximum flow rate of the quenching gas.

Les première et seconde températures de seuil dépendent de nombreux paramètres, notamment le type d'acier constituant la charge 14 et l'aire de la surface d'échange entre la charge 14 et le gaz de trempe. La détermination des première et seconde températures de seuil peut être effectuée en réalisant une trempe de la charge 14 avec une vitesse d'écoulement de gaz maximale de façon à déterminer la courbe 30 représentée en figure 2 associée à la charge 14. Les première et seconde températures de seuil correspondent alors à un pourcentage donné de la température maximale de la courbe 30. On peut alors pour un même type de charge mettre en oeuvre le premier exemple du procédé de la présente invention en prévoyant un capteur de température au niveau de la sortie de l'échangeur 22 relié à un microcontrôleur adapté à commander les moteurs 18. Les passages du premier palier de vitesse maximale 42 au palier de vitesse intermédiaire 44 et du palier de vitesse intermédiaire 44 au second palier de vitesse maximale 46 sont respectivement effectués lorsque la température du fluide de refroidissement dépasse la première température de seuil et diminue en dessous de la seconde température de seuil. Selon une autre variante, à partir de la courbe 30, on peut déterminer la durée T1 nécessaire pour que la température du fluide de refroidissement atteigne la première température de seuil. Il n'est pas alors nécessaire, en fonctionnement normal, de prévoir un capteur de température au niveau de l'échangeur 22, le passage du premier palier de vitesse maximale 42 au palier de vitesse intermédiaire 44 étant automatiquement réalisé au bout de la durée T1. Le passage du palier de vitesse intermédiaire 44 au second palier de vitesse maximale 46 peut alors être automatiquement réalisé au bout de la durée T2, déterminée, par exemple, de façon empirique.The first and second threshold temperatures depend on many parameters, including the type of steel constituting the charge 14 and the area of the exchange surface between the charge 14 and the quenching gas. The determination of the first and second threshold temperatures can be performed by quenching the charge 14 with a maximum gas flow rate so as to determine the curve shown in FIG. figure 2 14. The first and second threshold temperatures then correspond to a given percentage of the maximum temperature of the curve 30. It is then possible for the same type of charge to implement the first example of the process of the present invention. providing a temperature sensor at the outlet of the exchanger 22 connected to a microcontroller adapted to control the motors 18. The passages of the first maximum speed bearing 42 to the intermediate speed bearing 44 and the intermediate speed bearing 44 to the second maximum speed stage 46 are respectively performed when the temperature of the coolant exceeds the first threshold temperature and decreases below the second threshold temperature. According to another Alternatively, from curve 30, the time T1 necessary for the temperature of the coolant to reach the first threshold temperature can be determined. It is not then necessary, in normal operation, to provide a temperature sensor at the exchanger 22, the passage of the first maximum speed bearing 42 to the intermediate speed bearing 44 being automatically achieved at the end of the period T1 . The transition from the intermediate speed bearing 44 to the second maximum speed stage 46 can then be automatically performed after the duration T2, determined, for example, empirically.

Selon une variante du premier exemple de réalisation, le palier de vitesse intermédiaire 44 est maintenu même après que la température du fluide de refroidissement diminue en deçà de la seconde température de seuil donnée, telle que définie précédemment, vers la fin de la portion de faibles variations 50. Le passage du palier de vitesse intermédiaire 44 au second palier de vitesse maximale 46 n'est alors réalisé qu'après l'écoulement d'une durée supérieure à la durée T2 telle que définie précédemment. Selon une telle variante du premier exemple de réalisation, la courbe 42 comprend, après la portion de faibles variations 50, une portion descendante dont la pente est, en valeur absolue, plus faible que la pente de la portion descendante 52 représentée en figure 3 et qui se prolonge par une portion supplémentaire de faibles variations. A titre d'exemple, selon la variante du premier exemple de réalisation, le passage du palier de vitesse intermédiaire 44 au second palier de vitesse maximale 46 peut alors être réalisé lorsque la température du fluide de refroidissement diminue en deçà d'une température de seuil donnée qui est représentative du passage entre la portion descendante et la portion supplémentaire de faibles variations.According to a variant of the first exemplary embodiment, the intermediate speed bearing 44 is maintained even after the temperature of the cooling fluid decreases below the second given threshold temperature, as defined above, towards the end of the weak portion. Variations 50. The passage of the intermediate speed bearing 44 to the second level of maximum speed 46 is then performed only after the lapse of a duration greater than the duration T 2 as defined above. According to such a variant of the first exemplary embodiment, the curve 42 comprises, after the portion of small variations 50, a downward portion whose slope is, in absolute value, lower than the slope of the downward portion 52 represented in FIG. figure 3 and which is prolonged by an additional portion of small variations. By way of example, according to the variant of the first exemplary embodiment, the passage of the intermediate speed bearing 44 to the second maximum speed stage 46 can then be performed when the temperature of the cooling fluid falls below a threshold temperature. data that is representative of the passage between the descending portion and the additional portion of small variations.

La demanderesse a mis en évidence que le fait d'augmenter la durée du palier de vitesse intermédiaire 44, par rapport à la durée T2 telle que définie précédemment pour le premier exemple de réalisation, permet d'obtenir une amélioration de la résilience des pièces constituant la charge 14 trempée selon la variante du premier exemple de procédé de trempe de l'invention. L'amélioration de la résilience a, par exemple, été mise en évidence par des essais de résilience utilisant un mouton de Charpy. A titre d'exemple, en multipliant la durée T2, telle que définie précédemment pour le premier exemple de réalisation, par un facteur supérieur à 4, la demanderesse a observé une amélioration de la résilience supérieure à 20 %.The applicant has shown that increasing the duration of the intermediate speed bearing 44, compared to the duration T 2 as defined above for the first embodiment, makes it possible to obtain an improvement in the resilience of the parts constituting the quenched load 14 according to the variant of the first example of quenching process of the invention. The resilience improvement has, for example, been demonstrated by resilience tests using a Charpy sheep. By way of example, by multiplying the duration T 2 , as defined above for the first exemplary embodiment, by a factor greater than 4, the Applicant has observed an improvement in the resilience greater than 20%.

La présente invention propose également un deuxième exemple de procédé de trempe d'une charge 14 permettant de réduire les déformations de la charge 14 au cours de l'opération de trempe, notamment les déformations locales de la charge lorsque celle-ci comprend des pièces de formes complexes. Ceci permet de limiter les étapes de rectification ultérieures à prévoir pour les pièces trempées et/ou de simplifier les étapes préalables de conception des formes des pièces avant trempe.The present invention also proposes a second example of a process for quenching a load 14 making it possible to reduce the deformations of the load 14 during the quenching operation, in particular the local deformations of the load when the load comprises parts of the load. complex shapes. This makes it possible to limit the subsequent grinding steps to be provided for the quenched parts and / or to simplify the preliminary steps for designing the shapes of the parts before quenching.

La figure 5 représente une courbe 58 représentative de l'évolution de la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 pour le deuxième exemple de procédé de trempe selon l'invention et une courbe 60 représentative de l'évolution de la température du fluide de refroidissement de l'échangeur 22 obtenue avec un tel profil de vitesses du gaz de trempe. A titre de comparaison, on a reproduit, en traits pointillés, la courbe 30 d'évolution de la température du fluide de refroidissement pour un gaz de trempe circulant à vitesse maximale pendant la totalité de l'opération de trempe.The figure 5 represents a curve 58 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for the second example of quenching process according to the invention and a curve 60 representative of the evolution of the temperature of the quenching gas. exchanger cooling fluid 22 obtained with such a quenching gas velocity profile. By way of comparison, the curve 30 of evolution of the temperature of the cooling fluid for a quench gas circulating at maximum speed during the entire quenching operation has been reproduced in dotted lines.

Le deuxième exemple de réalisation du procédé de trempe de l'invention consiste à commander les moteurs 18 de sorte que la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 corresponde successivement à un premier palier de vitesse intermédiaire 62 pendant une durée T1' et à un palier de vitesse maximale 64 jusqu'à la fin de l'opération de trempe. A titre d'exemple, pendant le palier de vitesse intermédiaire 62, les moteurs 18 sont commandés de sorte que la vitesse d'écoulement du gaz de trempe varie entre 0 % et 70 % de la vitesse maximale. Pendant le palier 62, la courbe 60 d'évolution de la température du fluide de refroidissement comprend une portion ascendante 66 moins marquée que la portion ascendante 32 de la courbe 30. La température du fluide de refroidissement augmente donc moins vite que dans le cas où la vitesse de trempe est maximale. Lors du palier de vitesse maximale 64, la portion ascendante 66 se poursuit jusqu'à un sommet 68 et se prolonge par une portion descendante 70. La durée T1' peut s'étendre de 5 à 30 secondes suivant la durée totale de l'opération de trempe. En outre, la durée T1' peut être déterminée de façon empirique.The second embodiment of the quenching process of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 corresponds successively to a first intermediate speed stage 62 for a period of time. T1 'and at a maximum speed level 64 until the end of the quenching operation. For example, during the intermediate speed stage 62, the motors 18 are controlled so that the flow rate of the quenching gas varies between 0% and 70% of the maximum speed. During the plateau 62, the curve 60 of evolution of the temperature of the cooling fluid comprises an upward portion 66 less marked than the upward portion 32 of the curve 30. The temperature of the cooling fluid therefore increases less rapidly than in the case where the quenching speed is maximum. At the maximum speed stage 64, the ascending portion 66 continues to a vertex 68 and is extended by a downward portion 70. The duration T1 'can extend from 5 to 30 seconds depending on the total duration of the operation quenching. In addition, the duration T1 'can be determined empirically.

Pendant la durée T1', la vitesse de refroidissement de la charge 14 est inférieure à celle qui résulterait d'une vitesse maximale d'écoulement du gaz de trempe. Le refroidissement étant plus lent, les déformations de la charge 14 sont moins importantes. A l'achèvement de la durée T1', la charge s'étant refroidie, l'inertie mécanique de la charge 14 a augmenté. Une telle augmentation de l'inertie mécanique limite les déformations ultérieures de la charge 14 lorsqu'on augmente par la suite la vitesse d'écoulement du gaz de trempe. Les déformations locales de la charge 14, au cours de l'opération de trempe, sont donc globalement réduites puisque le refroidissement de la charge 14 avec la vitesse d'écoulement du gaz de trempe maximale est effectué lorsque la charge a déjà acquis une inertie mécanique suffisante et oppose donc une résistance supérieure aux déformations.During the period T1 ', the cooling rate of the charge 14 is lower than that which would result from a maximum flow rate of the quenching gas. Cooling being slower, the deformations of the load 14 are less important. At the completion of the duration T1 ', the load having cooled, the mechanical inertia of the load 14 has increased. Such an increase in the mechanical inertia limits the subsequent deformations of the load 14 when the flow rate of the quenching gas is subsequently increased. The local deformations of the charge 14, during the quenching operation, are thus reduced overall since the cooling of the charge 14 with the flow rate of the maximum quenching gas is performed when the charge has already acquired a mechanical inertia. sufficient and therefore opposes a higher resistance to deformations.

Dans le deuxième exemple de réalisation, la pression statique du gaz de trempe peut être maintenue constante pendant toute l'opération de trempe. Selon une variante, lors du passage du palier 62 de vitesse intermédiaire au palier 64 de vitesse maximale, une augmentation de la pression statique du gaz de trempe peut être prévue. La pression statique peut être augmentée de 2 à 5 fois la pression initiale pour atteindre une valeur, par exemple, entre 4 et 20 bars.In the second exemplary embodiment, the static pressure of the quenching gas can be kept constant throughout the quenching operation. According to a variant, during the transition from the intermediate speed bearing 62 to the maximum speed bearing 64, an increase in the static pressure of the quenching gas may be provided. The static pressure can be increased from 2 to 5 times the initial pressure to reach a value, for example, between 4 and 20 bar.

A titre d'exemple, pour une charge 14 comprenant des roues à dents hélicoïdales constituées d'un acier du type 15CrM6, la demanderesse a mis en évidence une réduction des déformations au niveau du profil des dents dans un plan perpendiculaire à la direction de l'hélice, pouvant atteindre environ 45 % par rapport à une trempe à l'huile chaude (huile à 180°C) et environ 30 % par rapport à une trempe au gaz à vitesse d'écoulement maximale du gaz de trempe.For example, for a load 14 comprising helical gear wheels made of a 15CrM6-type steel, the Applicant has shown a reduction of the deformations at the level of the profile of the teeth in a plane perpendicular to the direction of the helix, up to about 45% with respect to hot oil quenching (oil at 180 ° C) and about 30% with respect to gas quenching at maximum quenching gas flow rate.

La présente invention propose également un troisième exemple de procédé de trempe d'une charge 14 correspondant à la combinaison des deux exemples de réalisation précédemment décrits. Le troisième exemple de réalisation permet alors d'obtenir une amélioration de la tenue en fatigue des pièces constituant la charge et une réduction des déformations des pièces constituant la charge 14.The present invention also provides a third example of a process for quenching a filler 14 corresponding to the combination of the two previously described embodiments. The third exemplary embodiment then makes it possible to obtain an improvement in the fatigue strength of the parts constituting the load and a reduction in the deformations of the parts constituting the load 14.

La figure 6 représente une courbe 72 représentative de l'évolution de la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 pour le troisième exemple de procédé de trempe selon l'invention et une courbe 74 représentative de l'évolution de la température du fluide de refroidissement de l'échangeur 22 obtenue avec un tel profil de vitesses du gaz de trempe. A titre de comparaison, on a reproduit, en traits pointillés, la courbe 30 d'évolution de la température du fluide de refroidissement pour un gaz de trempe circulant à vitesse maximale pendant la totalité de l'opération de trempe.The figure 6 represents a curve 72 representative of the evolution of the flow rate of the quenching gas at the level of the charge 14 for the third example of quenching process according to the invention and a curve 74 representative of the evolution of the temperature of the quenching gas. exchanger cooling fluid 22 obtained with such a quenching gas velocity profile. By way of comparison, the curve 30 of evolution of the temperature of the cooling fluid for a quench gas circulating at maximum speed during the entire quenching operation has been reproduced in dotted lines.

Le troisième exemple de réalisation du procédé de trempe de l'invention consiste à commander les moteurs 18 de sorte que la vitesse d'écoulement du gaz de trempe au niveau de la charge 14 corresponde successivement à un palier de vitesse intermédiaire 76 pendant une durée T1", un palier de vitesse maximale 78 pendant une durée T2", un palier de vitesse intermédiaire 80 pendant une durée T3" et un palier de vitesse maximale 82 jusqu'à la fin de l'opération de trempe. A titre d'exemple, pendant le palier de vitesse intermédiaire 76, les moteurs 18 sont commandés de sorte que la vitesse d'écoulement du gaz de trempe varie entre 0 % et 70 % de la vitesse maximale et que, pendant le palier de vitesse intermédiaire 80, la vitesse d'écoulement du gaz de trempe varie entre 40 % et 70 % de la vitesse maximale.The third embodiment of the quenching process of the invention consists in controlling the motors 18 so that the flow rate of the quenching gas at the level of the charge 14 successively corresponds to an intermediate speed bearing 76 during a period T1 ", a maximum speed bearing 78 for a duration T2", an intermediate speed bearing 80 for a duration T3 "and a maximum speed bearing 82 until the end of the quenching operation. during the intermediate speed bearing 76, the motors 18 are controlled so that the flow velocity quenching gas varies between 0% and 70% of the maximum speed and during the intermediate speed stage 80, the flow rate of the quenching gas varies between 40% and 70% of the maximum speed.

Lors du palier 76, la courbe 74 d'évolution de la température du fluide de refroidissement comprend une portion ascendante 84 moins marquée que la portion ascendante 32 de la courbe 30. Lors du palier de vitesse maximale 78, la courbe 74 comprend une portion ascendante 86 plus marquée que la portion ascendante 84. Lors du palier de vitesse intermédiaire 80, la courbe 74 comprend un palier 88 de faibles variations et lors du palier de vitesse maximale 82, la courbe 74 comprend une portion descendante 90.During the stage 76, the curve 74 for changing the temperature of the cooling fluid comprises an upward portion 84 less marked than the upward portion 32 of the curve 30. At the maximum speed stage 78, the curve 74 comprises an ascending portion 86 at the intermediate speed bearing 80, the curve 74 comprises a bearing 88 of small variations and at the maximum speed bearing 82, the curve 74 comprises a downward portion 90.

Bien entendu, la présente invention est susceptible de diverses variantes et modifications qui apparaîtront à l'homme de l'art. En particulier, la cellule de trempe peut être différente de la cellule précédemment décrite. En particulier, l'axe des moteurs 18 peut être disposé selon l'horizontale, l'écoulement du gaz de trempe au niveau de la charge 14 se faisant sensiblement selon l'horizontale. En outre, la cellule peut comprendre un conduit formant une boucle à l'extérieur de la cellule, l'échangeur 22 étant inséré dans le conduit.Of course, the present invention is susceptible of various variations and modifications which will be apparent to those skilled in the art. In particular, the quenching cell may be different from the cell described above. In particular, the axis of the motors 18 may be arranged in the horizontal, the flow of the quenching gas at the load 14 is substantially in the horizontal. In addition, the cell may comprise a conduit forming a loop outside the cell, the exchanger 22 being inserted into the conduit.

Claims (7)

  1. A method for quenching a steel load (14) by flowing of a gas at the level of the load via gas moving means (18, 20), the gas, after having flowed at the level of the load (14), being cooled down by a exchanger (22) in which flows a cooling fluid, characterized in that the moving means are controlled to have the gas flow at the load level at a speed which varies according to a speed profile, at least a portion of which comprises, successively, a first plateau at a first speed (42), a second plateau at a second speed (44) inferior to the first speed and a third plateau at the first speed (46), the transition between the first plateau at the first speed and the second plateau at the second speed being performed during an increase phase of the cooling fluid temperature.
  2. The method of claim 1, wherein the static pressure of the gas at the level of the load (14) is decreased during the second plateau at the second speed (44; 80) with respect to the third plateau at the first speed (46; 82).
  3. The method of claim 1, wherein the moving means are controlled to have the gas flow at the level of the load (14) from the first plateau at the first speed (42) to the second plateau at the second speed (44) when the temperature of the cooling fluid reaches a given threshold temperature.
  4. The method of claim 1, wherein the moving means are controlled to have the gas flow at the level of the load (14) from the second plateau at the second speed (44) to the third plateau at the first speed (46) when the cooling fluid temperature decreases under a given additional threshold temperature.
  5. The method of claim 1, wherein the moving means are controlled to have the gas flow at the level of the load (14) from the first plateau at the first speed (42) to the second plateau at the second speed (44) after a determined time.
  6. The method of claim 1, wherein the moving means (18, 20) are controlled to have the gas flow at the load level according to a speed profile comprising, from the beginning of a quenching operation, successively a fourth plateau at a third speed (62) inferior to the first speed and the first plateau at the first speed (64), the transition between the fourth plateau at the third speed and the first plateau at the first speed being performed during an increase phase of the cooling fluid temperature.
  7. The method of claim 6, wherein the moving means are controlled to have the gas flow at the level of the load (14) from the fourth plateau at the third speed (62) to the first plateau at the first speed (64) after a determined time.
EP06709405.2A 2005-01-17 2006-01-16 Gas quenching cell for steel parts Active EP1844169B1 (en)

Applications Claiming Priority (2)

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FR0550134A FR2880898B1 (en) 2005-01-17 2005-01-17 GAS CUTTING CELL FOR STEEL PARTS
PCT/FR2006/050017 WO2006075120A1 (en) 2005-01-17 2006-01-16 Gas quenching cell for steel parts

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EP1844169B1 true EP1844169B1 (en) 2019-04-24

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CA (1) CA2595020A1 (en)
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SE0801263L (en) * 2007-05-29 2008-11-30 Indexator Ab Method & workpiece
JP4916545B2 (en) * 2009-12-21 2012-04-11 エジソンハード株式会社 Heat treatment equipment
JP6288413B2 (en) * 2013-10-11 2018-03-07 三菱重工業株式会社 A heat treatment method for stainless steel members and a method for producing stainless steel forgings.
CN111575460B (en) * 2020-07-02 2022-07-26 武汉轻工大学 Heat treatment cooling device
CN112556426B (en) * 2020-12-15 2022-08-23 江西科技学院 Sintering furnace with gas-phase quenching function and quenching process thereof

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JP2008527176A (en) 2008-07-24
EP1844169A1 (en) 2007-10-17
WO2006075120A1 (en) 2006-07-20
MX2007008652A (en) 2007-10-18
JP5638737B2 (en) 2014-12-10
CA2595020A1 (en) 2006-07-20
CN101107368A (en) 2008-01-16
FR2880898B1 (en) 2007-05-11
KR20070099648A (en) 2007-10-09
US20060157169A1 (en) 2006-07-20
BRPI0606652A2 (en) 2009-07-07
FR2880898A1 (en) 2006-07-21
BRPI0606652B1 (en) 2015-06-02

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