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WO2005108629A1 - Gas quenching method - Google Patents

Gas quenching method Download PDF

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Publication number
WO2005108629A1
WO2005108629A1 PCT/FR2005/000914 FR2005000914W WO2005108629A1 WO 2005108629 A1 WO2005108629 A1 WO 2005108629A1 FR 2005000914 W FR2005000914 W FR 2005000914W WO 2005108629 A1 WO2005108629 A1 WO 2005108629A1
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WO
WIPO (PCT)
Prior art keywords
gas
quenching
enclosure
water
treatment
Prior art date
Application number
PCT/FR2005/000914
Other languages
French (fr)
Inventor
Francis Pelissier
Original Assignee
Francis Pelissier
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Francis Pelissier filed Critical Francis Pelissier
Priority to EP05757129.1A priority Critical patent/EP1737989B1/en
Publication of WO2005108629A1 publication Critical patent/WO2005108629A1/en

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Classifications

    • 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
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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
    • 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
    • C21D1/60—Aqueous agents

Definitions

  • the invention relates to a method of quenching under gas of steel parts, having undergone a thermochemical treatment, by means of a flow of cooling gas obtained by introduction of its liquid phase in a gas quenching enclosure.
  • Quenching treatment has been used for many years to treat alloyed or high carbon steel parts. Such a treatment generally follows a thermochemical treatment consisting in enriching the surface of the pieces of low alloy steel.
  • the thermochemical treatment for example a carburizing or carbonitration treatment, can be done at low pressure, of the order of a few millibars, or at atmospheric pressure.
  • the quenching operation is generally carried out directly after the thermochemical treatment in an appropriate quenching cell. There are different types of quenching, the best known being gas quenching, oil quenching or salt bath quenching.
  • a main purpose of quenching is to obtain rapid cooling of the previously heated and treated parts, without altering their surface.
  • Gas quenching, particularly under neutral gas, is often preferred over other types of quenching, because it allows to obtain an excellent surface quality of the parts.
  • a low pressure carburizing treatment preceding the quenching treatment an absence of oxidation and intercrystalline corrosion is observed.
  • the quenching treatment under gas is carried out in a quenching cell 1 conventionally comprising an enclosure 2, capable of withstanding a vacuum and a pressurization of up to 50 bars, supported by a frame 3, a treatment chamber 4, into which the load to be treated 5 is introduced (at a temperature of the order of
  • the charge 5 may consist of a tool comprising one or more cemented parts.
  • the stirring element 6 may consist, for example, of a propeller or a centrifugal turbine driven in rotation by an electric motor.
  • the gas circulates in a closed loop 8, that is to say that it starts its course in the upper part of the enclosure 2, passes over the load 5 to be treated, heats up at contact of the load 5, then loses its calories through the heat exchanger 7, when it rises in the upper part of the enclosure 2.
  • the gas circulates in this loop 8 throughout the duration of the quenching treatment.
  • Such cells 1 are generally used when the quenching gas is not air but nitrogen, or a neutral gas, the quantities of which it is desirable to save. Some cells may also include an additional exchanger located outside the enclosure 2, which operates on the same principle as above.
  • a first solution consists in increasing the mass flow rate of the tempering.
  • two solutions are used, namely increasing the speed of circulation of the quenching gas and increasing the pressure of quenching gas.
  • quenching methods with a nitrogen pressure of the order of 20 bars and quenching methods with a helium or hydrogen pressure of the order of 50 to 60 bars have been proposed.
  • the quenching at the heart of the case-hardened parts turns out to be insufficient with conventional case-hardening steels.
  • document EP-A-1101826 describes a gas quenching process, after carburizing at low pressure, using air injected at high pressure.
  • An advantage of using air is that it is a free source of gas, available everywhere without special and inexhaustible conditioning.
  • the air used is generally depleted of oxygen to reduce the oxidation of the parts and the pressures used are of the same order as for pure nitrogen.
  • nitrogen constitutes an acceptable compromise in terms of cost and yield.
  • Nitrogen is indeed often preferred to hydrogen or neutral gases such as helium which, although lighter, therefore easier to transport under relatively high pressure, are very expensive (helium), or too dangerous (hydrogen).
  • hydrogen is considered to be the best cooling gas known to date, but it remains difficult to implement industrially (cost, storage, dangerousness).
  • Document EP-A-1367139 proposes the use of nitrogen or neutral gas in liquid form to improve the efficiency of the quenching process.
  • This document describes a heat treatment device comprising a useful chamber inside which is introduced a liquefied gas. The liquefied gas arrives in liquid form and is transformed into vapors inside the useful chamber.
  • the object of the invention is to remedy the aforementioned drawbacks and its object is to produce an effective gas quenching at low cost, with simple, light and risk-free equipment. According to the invention, this object is achieved by the appended claims and, more particularly, by the fact that the cooling gas is water vapor, obtained by evaporation of water introduced into the enclosure in liquid form.
  • the single FIGURE schematically represents a gas quenching cell allowing the implementation of a gas quenching process according to the invention.
  • the gas quenching cell 1 used for the quenching treatment according to the invention differs from the cells of the prior art by additional means associated with the implementation of the quenching treatment.
  • a reservoir 9 of a first gas for example nitrogen
  • a conduit 10 which introduces and projects the nitrogen inside the enclosure 2 at a predetermined pressure, of the order of 2 bars.
  • a water tank 11 is also connected to the enclosure 2 by means of at least one conduit 12, which introduces and projects the water in liquid form inside the enclosure 2 at a predetermined pressure. Water vaporizes in the enclosure 2 and the water vapor then constitutes the cooling gas.
  • Cell 1 also includes a discharge pipe 13, located in the lower part of enclosure 2 and intended, for example by means of a valve (not shown), to remove the condensates remaining at the bottom of the enclosure 2, after the end of the quenching treatment and the cooling of the cell 1.
  • the main advantage of such a quenching cell 1 lies in its ability to adapt to all existing installations, since the means necessary for the implementation of the quenching treatment, namely the reservoir 9 of the first gas, the water tank 11 and the inlet pipes 10, 12 and outlet 13, are simple, inexpensive and easy to install.
  • the gas quenching treatment according to the invention consists in introducing, through the conduit 12, the water in liquid phase, after having installed the charge 5 in the treatment chamber 4 of the cell 1.
  • the water is introduced in liquid phase until reaching the required quenching pressure, of the order of 20 to 30 bars.
  • Water is introduced in the liquid phase, to take advantage of both its cooling capacity once evaporated and the specific heat of evaporation of the liquid at the time of contact with hot parts.
  • a first gas inside the enclosure 2 preferably nitrogen.
  • the nitrogen gas is then introduced, simultaneously with the switching on of the stirring element 6, at a pressure of the order of 2 bars for a duration of the order of a few seconds.
  • the quenching treatment involves the introduction of nitrogen gas for a few seconds into the enclosure 2, followed by the introduction of water in the liquid phase.
  • the gases thus circulate in the enclosure 2 along the loop 8, which makes it possible to use only the quantity of nitrogen and water previously introduced during a quenching cycle and to avoid excessive and costly consumption.
  • the water therefore transforms into water vapor when it is introduced into the enclosure 2 and the pressure increases as more water is introduced.
  • the pressure drops until the water vapor has completely condensed. Below 100 ° C, the enclosure 2 then regains its initial pressure, namely that of the nitrogen gas introduced beforehand.
  • the condensates are evacuated through the conduit 13 located in the lower part of the cell 1, pushed by the residual pressure of the nitrogen introduced beforehand.
  • the quenching cycle described above thus preferably has a duration of the order of 15 to 20 minutes.
  • the quenching method according to the invention provides in particular the following advantages.
  • the parts are subjected to efficient cooling due to the specific heat of evaporation of water.
  • the efficiency of the quenching is optimal since it makes it possible to treat the core of the parts. Quenching does not create corrosion and does not cause cracks in the grain boundaries. No correction of the surface condition of the parts is necessary. Significant gains in terms of cost and simplicity are therefore observed.
  • the first gas in the tank 9 can be nitrogen or a neutral gas.
  • thermochemical treatment preceding the gas quenching treatment can be a low pressure carburizing treatment or a carburizing or carbonitriding treatment at atmospheric pressure.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

The invention relates to a method for the gas quenching of steel parts having undergone thermochemical treatment, which is performed with a cooling gas stream which is obtained by introducing the liquid phase thereof into a gas quenching chamber (2). The cooling gas comprises water vapour which is obtained by evaporating water introduced into the chamber (2) in liquid form. The inventive method can also comprise the introduction of a first gas before the introduction of the water in liquid form.

Description

Procédé de trempe sous gazGas quenching process
Domaine technique de l'inventionTechnical field of the invention
L'invention concerne un procédé de trempe sous gaz de pièces d'acier, ayant subi un traitement thermochimique, au moyen d'un flux de gaz de refroidissement obtenu par introduction de sa phase liquide dans une enceinte de trempe sous gaz.The invention relates to a method of quenching under gas of steel parts, having undergone a thermochemical treatment, by means of a flow of cooling gas obtained by introduction of its liquid phase in a gas quenching enclosure.
Etat de la techniqueState of the art
Le traitement de trempe est utilisé depuis de nombreuses années pour traiter des pièces d'acier allié ou à forte teneur en carbone. Un tel traitement fait généralement suite à un traitement thermochimique consistant à enrichir la surface des pièces en acier faiblement allié. Le traitement thermochimique, par exemple un traitement de cémentation ou de carbonitru ration, peut se faire à basse pression, de l'ordre de quelques millibars, ou à pression atmosphérique. L'opération de trempe est généralement effectuée directement après le traitement thermochimique dans une cellule de trempe appropriée. Il existe différents types de trempe, les plus connues étant la trempe sous gaz, la trempe à huile ou la trempe en bain de sel.Quenching treatment has been used for many years to treat alloyed or high carbon steel parts. Such a treatment generally follows a thermochemical treatment consisting in enriching the surface of the pieces of low alloy steel. The thermochemical treatment, for example a carburizing or carbonitration treatment, can be done at low pressure, of the order of a few millibars, or at atmospheric pressure. The quenching operation is generally carried out directly after the thermochemical treatment in an appropriate quenching cell. There are different types of quenching, the best known being gas quenching, oil quenching or salt bath quenching.
Un but principal de la trempe est d'obtenir un refroidissement rapide des pièces préalablement chauffées et traitées, sans altérer leur surface. La trempe sous gaz, particulièrement sous gaz neutre, est souvent préférée aux autres types de trempe, car elle permet d'obtenir une excellente qualité de surface des pièces. De plus, dans le cas d'un traitement de cémentation à basse pression précédant le traitement de trempe, une absence d'oxydation et de corrosion intercristalline est observée.A main purpose of quenching is to obtain rapid cooling of the previously heated and treated parts, without altering their surface. Gas quenching, particularly under neutral gas, is often preferred over other types of quenching, because it allows to obtain an excellent surface quality of the parts. In addition, in the case of a low pressure carburizing treatment preceding the quenching treatment, an absence of oxidation and intercrystalline corrosion is observed.
Comme représenté sur la figure unique, le traitement de trempe sous gaz s'effectue dans une cellule 1 de trempe comportant classiquement, une enceinte 2, pouvant supporter une mise sous vide et une mise sous pression pouvant aller jusqu'à 50 bars, supportée par un bâti 3, une chambre de traitement 4, dans laquelle est introduite la charge à traiter 5 (d'une température de l'ordre deAs shown in the single figure, the quenching treatment under gas is carried out in a quenching cell 1 conventionally comprising an enclosure 2, capable of withstanding a vacuum and a pressurization of up to 50 bars, supported by a frame 3, a treatment chamber 4, into which the load to be treated 5 is introduced (at a temperature of the order of
820°C à 1000°C), un élément de brassage 6 du gaz de trempe à l'intérieur de l'enceinte 2 et un échangeur calorifique 7. La charge 5 peut être constituée d'un outillage comportant une ou plusieurs pièces cémentées. L'élément de brassage 6 peut être constitué, par exemple, d'une hélice ou d'une turbine centrifuge entraînée en rotation par un moteur électrique.820 ° C to 1000 ° C), a stirring element 6 of the quenching gas inside the enclosure 2 and a heat exchanger 7. The charge 5 may consist of a tool comprising one or more cemented parts. The stirring element 6 may consist, for example, of a propeller or a centrifugal turbine driven in rotation by an electric motor.
Dans une telle cellule de trempe 1 , le gaz circule selon une boucle fermée 8, c'est-à-dire qu'il démarre son parcours en partie haute de l'enceinte 2, passe sur la charge 5 à traiter, se réchauffe au contact de la charge 5, puis perd ses calories à travers l'échangeur calorifique 7, quand il remonte en partie haute de l'enceinte 2. Le gaz circule selon cette boucle 8 pendant toute la durée du traitement de trempe. De telles cellules 1 sont généralement utilisées quand le gaz de trempe n'est pas de l'air mais de l'azote, ou un gaz neutre, dont il est souhaitable d'économiser les quantités utilisées. Certaines cellules peuvent comporter également un échangeur supplémentaire situé à l'extérieur de l'enceinte 2, qui fonctionne suivant le même principe que précédemment.In such a quenching cell 1, the gas circulates in a closed loop 8, that is to say that it starts its course in the upper part of the enclosure 2, passes over the load 5 to be treated, heats up at contact of the load 5, then loses its calories through the heat exchanger 7, when it rises in the upper part of the enclosure 2. The gas circulates in this loop 8 throughout the duration of the quenching treatment. Such cells 1 are generally used when the quenching gas is not air but nitrogen, or a neutral gas, the quantities of which it is desirable to save. Some cells may also include an additional exchanger located outside the enclosure 2, which operates on the same principle as above.
Pour obtenir la dureté souhaitée à la surface et au cœur des pièces cémentées, une première solution consiste à augmenter le débit massique du gaz de trempe. Pour augmenter le débit massique, deux solutions sont utilisées, à savoir l'augmentation de la vitesse de circulation du gaz de trempe et l'augmentation de la pression de gaz de trempe.To obtain the desired hardness at the surface and at the heart of the case-hardened parts, a first solution consists in increasing the mass flow rate of the tempering. To increase the mass flow, two solutions are used, namely increasing the speed of circulation of the quenching gas and increasing the pressure of quenching gas.
Ainsi, des procédés de trempe avec une pression d'azote de l'ordre de 20 bars et des procédés de trempe avec une pression d'hélium ou d'hydrogène de l'ordre de 50 à 60 bars ont été proposés. Cependant, la trempe au cœur des pièces cémentées s'avère être insuffisante avec les aciers classiques de cémentation.Thus, quenching methods with a nitrogen pressure of the order of 20 bars and quenching methods with a helium or hydrogen pressure of the order of 50 to 60 bars have been proposed. However, the quenching at the heart of the case-hardened parts turns out to be insufficient with conventional case-hardening steels.
Il est également souhaitable de réduire le coût du traitement de trempe qui, en raison de l'atmosphère gazeuse à maintenir et du débit massique requis, n'est pas négligeable dans le coût global du traitement des pièces.It is also desirable to reduce the cost of the quenching treatment which, due to the gaseous atmosphere to be maintained and the mass flow required, is not negligible in the overall cost of treating the parts.
À cet effet, le document EP-A-1101826 décrit un procédé de trempe sous gaz, après cémentation à basse pression, utilisant de l'air injecté à une pression élevée. Un avantage de l'utilisation de l'air est qu'il s'agit d'une source de gaz gratuite, disponible partout sans conditionnement particulier et inépuisable. L'air utilisé est généralement appauvri en oxygène pour diminuer l'oxydation des pièces et les pressions utilisées sont du même ordre que pour de l'azote pur.To this end, document EP-A-1101826 describes a gas quenching process, after carburizing at low pressure, using air injected at high pressure. An advantage of using air is that it is a free source of gas, available everywhere without special and inexhaustible conditioning. The air used is generally depleted of oxygen to reduce the oxidation of the parts and the pressures used are of the same order as for pure nitrogen.
Ainsi, le coût des étapes de trempe est considérablement réduit par rapport aux procédés classiques. Cependant, l'efficacité de la trempe est médiocre et une oxydation des pièces est encore observée.Thus, the cost of the quenching steps is considerably reduced compared to conventional methods. However, the quenching efficiency is poor and oxidation of the parts is still observed.
Parmi tous les gaz de trempe généralement utilisés, l'azote constitue un compromis acceptable en termes de coût et de rendement. L'azote est en effet souvent préféré à l'hydrogène ou à des gaz neutres tel que l'hélium qui, bien que plus légers, donc plus faciles à véhiculer sous une pression relativement élevée, sont très coûteux (hélium), ou trop dangereux (hydrogène). À titre d'exemple, l'hydrogène est considéré comme le meilleur gaz de refroidissement connu à ce jour, mais il reste difficile à mettre en œuvre industriellement (coût, stockage, dangerosité).Among all the quenching gases generally used, nitrogen constitutes an acceptable compromise in terms of cost and yield. Nitrogen is indeed often preferred to hydrogen or neutral gases such as helium which, although lighter, therefore easier to transport under relatively high pressure, are very expensive (helium), or too dangerous (hydrogen). As for example, hydrogen is considered to be the best cooling gas known to date, but it remains difficult to implement industrially (cost, storage, dangerousness).
Cependant, les inconvénients du recours à l'azote comme gaz de refroidissement sont, d'une part le coût, et, d'autre part, la nécessité d'acheminement et de stockage de volumes importants de gaz par des équipements lourds, compliqués, onéreux et consommateurs d'énergie.However, the drawbacks of using nitrogen as a cooling gas are, on the one hand, the cost, and, on the other hand, the need to transport and store large volumes of gas by heavy, complicated equipment, expensive and energy consuming.
Par ailleurs, quel que soit le gaz de refroidissement employé, le procédé de trempe s'avère le plus souvent inefficace.Furthermore, whatever the cooling gas used, the quenching process is most often ineffective.
Le document EP-A-1367139 propose l'utilisation d'azote ou de gaz neutre sous forme liquide pour améliorer l'efficacité du procédé de trempe. Ce document décrit un dispositif de traitement thermique comportant une chambre utile à l'intérieur de laquelle est introduit un gaz liquéfié. Le gaz liquéfié arrive sous forme liquide et est transformé en vapeurs à l'intérieur de la chambre utile.Document EP-A-1367139 proposes the use of nitrogen or neutral gas in liquid form to improve the efficiency of the quenching process. This document describes a heat treatment device comprising a useful chamber inside which is introduced a liquefied gas. The liquefied gas arrives in liquid form and is transformed into vapors inside the useful chamber.
Cependant, l'efficacité d'un tel procédé de trempe, avec l'introduction d'azote ou de gaz neutre liquéfié, reste insuffisante. Le stockage et l'acheminement des gaz de refroidissement sous forme liquide restent également problématiques.However, the efficiency of such a quenching process, with the introduction of nitrogen or liquefied neutral gas, remains insufficient. The storage and transport of cooling gases in liquid form also remains problematic.
Objet de l'inventionSubject of the invention
L'invention a pour but de remédier aux inconvénients précités et a pour objet la réalisation d'une trempe sous gaz efficace et à faible coût, avec des équipements simples, légers et sans risque. Selon l'invention, ce but est atteint par les revendications annexées et, plus particulièrement, par le fait que le gaz de refroidissement est de la vapeur d'eau, obtenue par évaporation d'eau introduite dans l'enceinte sous forme liquide.The object of the invention is to remedy the aforementioned drawbacks and its object is to produce an effective gas quenching at low cost, with simple, light and risk-free equipment. According to the invention, this object is achieved by the appended claims and, more particularly, by the fact that the cooling gas is water vapor, obtained by evaporation of water introduced into the enclosure in liquid form.
Description sommaire des dessinsBrief description of the drawings
D'autres avantages et caractéristiques ressortiront plus clairement de la description qui va suivre d'un mode particulier de réalisation de l'invention donné à titre d'exemple non limitatif et représenté au dessin annexé, dans lequel :Other advantages and characteristics will emerge more clearly from the description which follows of a particular embodiment of the invention given by way of nonlimiting example and represented in the appended drawing, in which:
La figure unique représente schématiquement une cellule de trempe sous gaz permettant la mise en œuvre d'un procédé de trempe sous gaz selon l'invention.The single FIGURE schematically represents a gas quenching cell allowing the implementation of a gas quenching process according to the invention.
Description de modes particuliers de réalisationDescription of particular embodiments
Sur la figure unique, la cellule 1 de trempe sous gaz utilisée pour le traitement de trempe selon l'invention se différencie des cellules de l'art antérieur par des moyens supplémentaires associés à la mise en œuvre du traitement de trempe. Ainsi, un réservoir 9 d'un premier gaz, par exemple de l'azote, est relié à l'enceinte 2 par l'intermédiaire d'au moins un conduit 10, qui introduit et projette l'azote à l'intérieur de l'enceinte 2 à une pression prédéterminée, de l'ordre de 2 bars.In the single figure, the gas quenching cell 1 used for the quenching treatment according to the invention differs from the cells of the prior art by additional means associated with the implementation of the quenching treatment. Thus, a reservoir 9 of a first gas, for example nitrogen, is connected to the enclosure 2 by means of at least one conduit 10, which introduces and projects the nitrogen inside the enclosure 2 at a predetermined pressure, of the order of 2 bars.
Un réservoir 11 d'eau est également relié à l'enceinte 2 par l'intermédiaire d'au moins un conduit 12, qui introduit et projette l'eau sous forme liquide à l'intérieur de l'enceinte 2 à une pression prédéterminée. L'eau se vaporise dans l'enceinte 2 et la vapeur d'eau constitue alors le gaz de refroidissement. La cellule 1 comporte aussi un conduit 13 d'évacuation, situé en partie basse de l'enceinte 2 et destiné, par exemple par l'intermédiaire d'une vanne (non représentée), à éliminer les condensats restants au fond de l'enceinte 2, après la fin du traitement de trempe et le refroidissement de la cellule 1.A water tank 11 is also connected to the enclosure 2 by means of at least one conduit 12, which introduces and projects the water in liquid form inside the enclosure 2 at a predetermined pressure. Water vaporizes in the enclosure 2 and the water vapor then constitutes the cooling gas. Cell 1 also includes a discharge pipe 13, located in the lower part of enclosure 2 and intended, for example by means of a valve (not shown), to remove the condensates remaining at the bottom of the enclosure 2, after the end of the quenching treatment and the cooling of the cell 1.
L'avantage principal d'une telle cellule de trempe 1 réside dans sa capacité à s'adapter à toutes les installations existantes, car les moyens nécessaires à la mise en œuvre du traitement de trempe, à savoir le réservoir 9 de premier gaz, le réservoir 11 d'eau et les conduits d'introduction 10, 12 et d'évacuation 13, sont simples, peu coûteux et faciles d'installation.The main advantage of such a quenching cell 1 lies in its ability to adapt to all existing installations, since the means necessary for the implementation of the quenching treatment, namely the reservoir 9 of the first gas, the water tank 11 and the inlet pipes 10, 12 and outlet 13, are simple, inexpensive and easy to install.
Le traitement de trempe sous gaz selon l'invention consiste, à introduire, par le conduit 12, l'eau en phase liquide, après avoir installé la charge 5 dans la chambre de traitement 4 de la cellule 1. L'eau est introduite en phase liquide jusqu'à atteindre la pression de trempe requise, de l'ordre de 20 à 30 bars.The gas quenching treatment according to the invention consists in introducing, through the conduit 12, the water in liquid phase, after having installed the charge 5 in the treatment chamber 4 of the cell 1. The water is introduced in liquid phase until reaching the required quenching pressure, of the order of 20 to 30 bars.
L'eau est introduite en phase liquide, pour profiter à la fois de sa capacité de refroidissement une fois évaporé et de la chaleur spécifique d'évaporation du liquide au moment du contact avec les pièces chaudes.Water is introduced in the liquid phase, to take advantage of both its cooling capacity once evaporated and the specific heat of evaporation of the liquid at the time of contact with hot parts.
Il est possible, avant l'introduction de l'eau en phase liquide, d'introduire un premier gaz à l'intérieur de l'enceinte 2, de préférence, de l'azote. L'azote gazeux est alors introduit, simultanément avec la mise en route de l'élément de brassage 6, à une pression de l'ordre de 2 bars pendant une durée de l'ordre de quelques secondes.It is possible, before the introduction of water in the liquid phase, to introduce a first gas inside the enclosure 2, preferably nitrogen. The nitrogen gas is then introduced, simultaneously with the switching on of the stirring element 6, at a pressure of the order of 2 bars for a duration of the order of a few seconds.
Selon un mode particulier de réalisation, le traitement de trempe comporte l'introduction d'azote gazeux pendant quelques secondes dans l'enceinte 2, suivi de l'introduction d'eau en phase liquide. L'eau se vaporise rapidement au contact de la charge 5 et le brassage selon la boucle 8 s'effectue donc avec l'azote gazeux et la vapeur d'eau pendant la durée nécessaire à la baisse de température de l'enceinte 2.According to a particular embodiment, the quenching treatment involves the introduction of nitrogen gas for a few seconds into the enclosure 2, followed by the introduction of water in the liquid phase. The water vaporizes rapidly on contact with the load 5 and the stirring along the loop 8 is therefore carried out with nitrogen gas and water vapor for the time necessary for the temperature of the enclosure 2 to drop.
Les gaz circulent ainsi dans l'enceinte 2 selon la boucle 8, ce qui permet d'utiliser uniquement la quantité d'azote et d'eau préalablement introduite pendant un cycle de trempe et d'éviter une consommation trop importante et trop coûteuse.The gases thus circulate in the enclosure 2 along the loop 8, which makes it possible to use only the quantity of nitrogen and water previously introduced during a quenching cycle and to avoid excessive and costly consumption.
L'eau se transforme donc en vapeur d'eau lors de son introduction dans l'enceinte 2 et la pression augmente au fur et à mesure de l'introduction d'une quantité d'eau plus importante. Lorsque les pièces à traiter se refroidissent, la pression baisse jusqu'à la condensation complète de la vapeur d'eau. En dessous de 100°C, l'enceinte 2 retrouve alors sa pression initiale, à savoir celle de l'azote gazeux introduit préalablement.The water therefore transforms into water vapor when it is introduced into the enclosure 2 and the pressure increases as more water is introduced. When the parts to be treated cool, the pressure drops until the water vapor has completely condensed. Below 100 ° C, the enclosure 2 then regains its initial pressure, namely that of the nitrogen gas introduced beforehand.
Après l'arrêt de l'élément de brassage 6, les condensats sont évacués par le conduit 13 situé en partie basse de la cellule 1 , poussés par la pression résiduelle de l'azote introduit au préalable.After stopping the stirring element 6, the condensates are evacuated through the conduit 13 located in the lower part of the cell 1, pushed by the residual pressure of the nitrogen introduced beforehand.
Le cycle de trempe décrit ci-dessus présente ainsi, de préférence, une durée de l'ordre de 15 à 20 minutes.The quenching cycle described above thus preferably has a duration of the order of 15 to 20 minutes.
Grâce à l'utilisation de la vapeur d'eau comme gaz de refroidissement, la consommation d'azote est ainsi réduite, de l'ordre de 70% à 80%, ce qui entraîne une réduction notable du coût de traitement. Le procédé de trempe selon l'invention procure notamment les avantages suivants. Les pièces sont soumises à un refroidissement efficace du fait de la chaleur spécifique d'évaporation de l'eau. L'efficacité de la trempe est optimale puisqu'elle permet de traiter le cœur des pièces. La trempe ne crée pas de corrosion et ne provoque pas de fissures au joint de grains. Aucune rectification de l'état de surface des pièces n'est nécessaire. Des gains sensibles en termes de coût et de simplicité sont donc observés.Thanks to the use of water vapor as a cooling gas, nitrogen consumption is thus reduced, of the order of 70% to 80%, which results in a significant reduction in the cost of treatment. The quenching method according to the invention provides in particular the following advantages. The parts are subjected to efficient cooling due to the specific heat of evaporation of water. The efficiency of the quenching is optimal since it makes it possible to treat the core of the parts. Quenching does not create corrosion and does not cause cracks in the grain boundaries. No correction of the surface condition of the parts is necessary. Significant gains in terms of cost and simplicity are therefore observed.
L'utilisation de la vapeur d'eau pour tremper sous gaz des pièces mécaniques, notamment dans le cas de pièces cémentées, engendre des gains importants en termes de coût et de durée, compte tenu de la disponibilité de l'eau et de son efficacité de refroidissement.The use of water vapor for quenching mechanical parts under gas, in particular in the case of hardened parts, generates significant savings in terms of cost and duration, taking into account the availability of water and its efficiency. cooling.
L'invention n'est pas limitée au mode de réalisation décrit ci-dessus. Notamment, le premier gaz du réservoir 9 peut être de l'azote ou un gaz neutre.The invention is not limited to the embodiment described above. In particular, the first gas in the tank 9 can be nitrogen or a neutral gas.
Le traitement thermochimique précédant le traitement de trempe sous gaz peut être un traitement de cémentation basse pression ou un traitement de cémentation ou carbonitruration à pression atmosphérique. The thermochemical treatment preceding the gas quenching treatment can be a low pressure carburizing treatment or a carburizing or carbonitriding treatment at atmospheric pressure.

Claims

Revendications claims
1. Procédé de trempe sous gaz de pièces d'acier, ayant subi un traitement thermochimique, au moyen d'un flux de gaz de refroidissement obtenu par introduction de sa phase liquide dans une enceinte (2) de trempe sous gaz, procédé caractérisé en ce que le gaz de refroidissement est de la vapeur d'eau, obtenue par évaporation d'eau introduite dans l'enceinte (2) sous forme liquide.1. A method of tempering steel parts under gas, having undergone a thermochemical treatment, by means of a flow of cooling gas obtained by introducing its liquid phase into a gas quenching enclosure (2), method characterized in what the cooling gas is water vapor, obtained by evaporation of water introduced into the enclosure (2) in liquid form.
2. Procédé selon la revendication 1 , caractérisé en ce que l'eau est injectée dans l'enceinte (2) à une pression permettant à l'enceinte (2) d'atteindre une pression de l'ordre de 20 à 30 bars.2. Method according to claim 1, characterized in that the water is injected into the enclosure (2) at a pressure allowing the enclosure (2) to reach a pressure of the order of 20 to 30 bars.
3. Procédé selon l'une des revendications 1 et 2, caractérisé en ce qu'il comporte une introduction préalable d'un premier gaz dans l'enceinte (2), avant l'introduction de l'eau.3. Method according to one of claims 1 and 2, characterized in that it comprises a prior introduction of a first gas into the enclosure (2), before the introduction of water.
4. Procédé selon la revendication 3, caractérisé en ce que le premier gaz est injecté à une pression de l'ordre de 2 bars pendant quelques secondes.4. Method according to claim 3, characterized in that the first gas is injected at a pressure of the order of 2 bars for a few seconds.
5. Procédé selon l'une des revendications 3 et 4, caractérisé en ce que le premier gaz est de l'azote.5. Method according to one of claims 3 and 4, characterized in that the first gas is nitrogen.
6. Procédé selon l'une des revendications 3 et 4, caractérisé en ce que le premier gaz est un gaz neutre.6. Method according to one of claims 3 and 4, characterized in that the first gas is a neutral gas.
7. Procédé selon l'une quelconque des revendications 1 à 6, caractérisé en ce que la durée d'un cycle de trempe est de l'ordre de 15 à 20 minutes. 7. Method according to any one of claims 1 to 6, characterized in that the duration of a quenching cycle is of the order of 15 to 20 minutes.
PCT/FR2005/000914 2004-04-19 2005-04-15 Gas quenching method WO2005108629A1 (en)

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EP1737989B1 (en) 2014-11-05

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