EP1162279A1 - Gas-heated carburising installation - Google Patents

Gas-heated carburising installation Download PDF

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Publication number
EP1162279A1
EP1162279A1 EP01410062A EP01410062A EP1162279A1 EP 1162279 A1 EP1162279 A1 EP 1162279A1 EP 01410062 A EP01410062 A EP 01410062A EP 01410062 A EP01410062 A EP 01410062A EP 1162279 A1 EP1162279 A1 EP 1162279A1
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EP
European Patent Office
Prior art keywords
cell
gas
heat treatment
burners
preheating
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Granted
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EP01410062A
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German (de)
French (fr)
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EP1162279B1 (en
Inventor
Max Eymin
Laurent Pelissier
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Etudes et Constructions Mecaniques SA
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Etudes et Constructions Mecaniques SA
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D99/00—Subject matter not provided for in other groups of this subclass
    • F27D99/0001—Heating elements or systems
    • F27D99/0033—Heating elements or systems using burners
    • F27D99/0035—Heating indirectly through a radiant surface
    • 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
    • C21D1/773—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material under reduced pressure or vacuum
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising

Definitions

  • the present invention relates to the treatment of parts steel, and more precisely the carburizing heat treatment, i.e. introduction of carbon into the surface parts to improve its hardness.
  • the invention relates more particularly vacuum cementation plants or under low pressure (below atmospheric pressure).
  • a low pressure carburizing treatment consists of to submit the parts to be treated, in a sealed enclosure to the air, alternating enrichment stages in the presence a low pressure carburizing gas and diffusion steps vacuum or neutral atmosphere at low pressure.
  • the respective durations of enrichment and dissemination stages as well as their number depend in particular on the concentration in carbon and the desired cementation depth in the parts, and these treatments are well known in the art.
  • a example of low pressure carburizing process is described in French patent application No. 2,678,287 of the applicant.
  • Any case hardening treatment is a heat treatment at high temperature (generally, of the order of 800 to 1000 ° C, or more) and heating as well as maintaining the temperature homogeneous parts during the diffusion and enrichment stages constitute a key point in the case hardening processes.
  • the invention also refers to carbonitriding whose only difference compared to the case hardening comes from enrichment gas used to which is generally added ammonia. The result is the formation of nitride (instead of carbide for cementation) on the surface of the part. We will note so that everything that will be exposed later in relation to the carburizing also applies to carbonitriding.
  • the carburizing chambers define volumes of one or more cubic meters which are heated and maintained at the carburizing temperature by means of Electric heating.
  • resistors electrical in the form of bars that are distributed around the periphery.
  • the volume of carburizing that is to say around the chamber cementation, depending on the desired thermal distribution as well as thermal bridges linked to the constitution of the chamber.
  • the first energy that comes to mind is the gas that is "clean" and inexpensive energy.
  • the use gas in the heating of cementation chambers a large number of problems that have led so far to prefer electric heating, especially for installations at low pressure.
  • a first problem is linked to the very constitution of gas burners, which must heat the internal space of the enclosure without introducing gas combustion smoke into it.
  • the necessary length of the burners due to the large dimensions of the carburizing chambers is a critical point in terms of heat distribution in the enclosure.
  • the type of gas burner system that would be suitable to use corresponds, for example, to the burner system described in French patent application No. 2,616,520.
  • This type of system with burner consists of a sealed outer casing and a central hearth tube defining a combustion chamber.
  • a such a system uses a recirculation of the burnt gases and allows a high speed output of these gases.
  • This burner system can if necessary be associated with an internal tube of the type described in French patent application No. 2,616,518.
  • the contents respective of the above publications are considered known.
  • An object of the present invention is to provide a gas-heated cementation cell which overcomes the disadvantages mentioned above.
  • Another object of the present invention is to provide a solution that is compatible with the current distribution of heating means at the periphery of a cementation cell.
  • Another object of the present invention is to provide a modular cementation system which takes advantage of the use of gas as a source of heating energy.
  • the present invention provides a low pressure heat treatment cell of steel parts, comprising heating means consisting of several gas radiant tubes distributed around a useful volume a sealed enclosure; and control means provided with the less than one pulse control mode of the heating means.
  • control means are suitable for controlling the means of heating according to two operating phases respectively of preheating at full power and maintaining temperature in pulse regulation.
  • control means are suitable for modifying the gas flow rate between two levels respectively maximum for preheating and intermediate for pulse regulation.
  • all gas radiant tubes are ordered individually or by groups.
  • control means include a programmable controller for individualize orders for the different tubes.
  • the present invention also provides an installation for low pressure heat treatment of steel parts comprising several treatment cells connected to an enclosure watertight joint provided with handling means for transferring a charge from one cell to another, at least one cell being of the aforementioned type.
  • At least one cell is dedicated to preheating a load to case, and at least one cell is a case cell.
  • the cementation cell is provided with heating means gases suitable for being controlled in pulse control mode.
  • a feature of the present invention is provide impulse control of gas burners in a cell heat treatment, at least during temperature maintenance after a preheating phase.
  • gas burners of the type used are used described in the aforementioned French patent application No. 2,616,520, and we control these burners so as to obtain, at least after a preheating phase, timed regulation.
  • a switching between two air and gas flows according to the mode of burner operation is carried out according to the invention.
  • burners are provided.
  • two air and gas flows allowing operation in a first maximum flow for a preheating phase and a operation in a second intermediate flow for the phase of regulation.
  • the intermediate flow does not does not correspond to the minimum burner flow rate, so that both flow rates allow acceptable temperature uniformity, with correct recovery of the fumes in the burner.
  • FIG. 1 represents an embodiment of the present invention. This figure illustrates, very partially, a heat treatment cell in that it represents a single gas burner 1 as well as the system 2 for controlling cell gas burners.
  • the gas burner 1 essentially consists of a external radiant envelope 10 in the form of a glove which passes through, by means of a vacuum sealing system 11, the wall 12 of the treatment cell.
  • the burner has also a tube 13, internal to the casing 10 and coaxial with this one.
  • a first end of the tube 13 is close to the end of the casing 10 in the carburizing cell.
  • a second end of tube 13 is open towards an outlet a chamber 14 intended to produce the gas-air mixture of burner and combustion.
  • the burner is preferably recirculating the fumes, that is to say that part of the combustion fumes is used to be reintroduced at the inlet of tube 13, the rest of the fumes being evacuated by a vent 15 from the envelope 10 outside of the cell.
  • Room 14 has at least one gas supply 16 and at least one gas supply 17 air. Generally, several air intakes are planned to better homogenize the gas-air mixture to be burned.
  • the conduits 16 and 17 of air intake exit from the envelope 10 to the outside of the cementation cell.
  • the position of the burner 1 relative to the wall of the enclosure 12 is such that the entire tube 13 is contained in the internal volume of the cementation cell.
  • the entire tube 13 is preferably not contained in the so-called "hot" volume of the cementation enclosure which is generally delimited by a heat shield (symbolized with a dotted line 18).
  • room 14 itself is in the internal volume of the cell, but preferably out of the hot volume.
  • the position of burner 1 is chosen for that the part of the tube 13 in the hot volume is homogeneous in temperature.
  • the position of the burner is adjusted by moving all of it (including envelope 10) compared to the wall 12 of the enclosure, to adjust the position of the inlet of the tube 13 relative to the heat shield 18.
  • System 2 essentially comprises a circuit electronic regulation (REG) 20 (in practice, one or more circuits) and a network 21 of valves controlled by circuit 20, if necessary via a programmable controller 30 (AUTO) as we will see later.
  • REG circuit electronic regulation
  • AUTO programmable controller 30
  • circuit 20 receives measurement signals 22 and control.
  • the measurement signals are essentially made up measurement results supplied by at least one temperature of the carburizing chamber.
  • Control signals come from a control center accessible by the operator.
  • the regulation circuit 20 (or the automaton 30) delivers control signals 23 to the gas burners for ignite and extinguish their respective flames.
  • the circuit 20 controls also the network 21 of gas and air valves.
  • This network of valves is used to control the respective gas and air flow rates of the different burners.
  • valve structure illustrated by the Figure 1 is preferably reproduced for each burner.
  • a main gas supply pipe 24 is divided into two pipes 25 and 26 respectively associated with limiters 25-1 and 26-1.
  • the lines 25 and 26 have, according to the invention, different bit rates.
  • line 25 is intended to supply, in association with the limiter 25-1, a flow maximum gas for burner operation in power maximum during at least one preheating phase.
  • Driving 26 is intended to provide, in association with the limiter 26-1, a lower gas flow rate for burner operation in the timed scheme of the invention.
  • a pipe main 27 is divided into two pipes 28 and 29 respectively associated with limiters 28-1 and 29-1 whose roles are similar to those exposed above in relation to food in gas.
  • the flow rates imposed by the limiters 25-1, 26-1, 28-1 and 29-1 are preset.
  • each of the pipes 25, 26, 28 and 29 is associated with a control valve 25-2, 26-2, 28-2 and 29-2 in all or nothing.
  • Valves 26-2 and 29-2 are preferably simultaneously controlled by a signal 32 delivered by the circuit 20 (or by the automaton 30) in clocked mode.
  • Valves 25-2 and 28-2 are preferably controlled simultaneously by a signal 33 from circuit 20 or from automaton 30.
  • the ends of the pipes 25, 26 and 28, 29 are joined at their opposite ends respective.
  • FIG. 2 represents, in the form of chronograms, an example of pace signal 33, signal 32 and instantaneous power P gas burners.
  • valves 25-2 and 28-2 are open at maximum flow.
  • provision may be made for the maximum flow rate to be fixed by the sum of the flow rates of all limiters.
  • the valves 26-2 and 29-2 are also open.
  • an intermediate phase instant t1 to t2 during which the burner power goes to the lower flow without timing. To do this, from time t1, the burner 1 operates in intermediate power regime.
  • control signal 33 changes state in order to close the valves 25-2 and 28-2 and signal 32 changes state to open (if they are not already) valves 26-2 and 29-2.
  • the instant t1 is set by approaching a temperature setpoint below the desired control temperature.
  • the intermediate phase between times t1 and t2 can, in particular, be used to avoid the temperature setpoint exceeded due to inertia of the system.
  • the clocked regulation signal 32 adapts, in function of the parameters that the circuit 20 receives by the signals 22, the respective opening times of valves 26-2 and 29-2.
  • the desired power for the burner is relatively large and requires pulses of duration relatively long. It can be, for example, a phase adaptation of the burner power change between its maximum and intermediate levels. From time t3, we can consider that we are in a regulatory phase proper where the duty cycle of the ignition pulses of the burner depends exclusively on temperature variations in the carburizing chamber. These variations can come from, for example, of a modification imposed by the process of carburizing or charge transfer in the cell.
  • the ignition times and the stop times respective burners are established, among other things, according to the arrangement of the burners in the enclosure and their constitution.
  • the burners can be ordered in clocked mode even during their operation in full power.
  • the controller 30 provides individual commands (signals 32 'and 33' to destination other burners not shown), for example by differing igniting the burners successively and adjusting the times ignition pulses to the different burners.
  • the automaton 30 has a pre-established functioning and receives, among other things, control signals 34 and 35 from the regulator which are common to all burners, the automaton taking charge of adapting these signals to the different burners.
  • the different burners will be distributed in the cementation cell according to the desired thermal uniformity.
  • the homogeneity adjustments essentially depend on the choice of the intermediate power which is a function of the length of burners, therefore the volume of the enclosure.
  • the burners may be controlled by groups.
  • Figure 3 illustrates an example of application of the present invention to a modular installation of cells case hardening.
  • the embodiment of Figure 3 is inspired a modular installation as described in the request for European patent N ° 0 922 778 of the applicant that we consider as known.
  • a basic module 40 includes a sealed enclosure 41 in the form of a cylinder (not necessarily circular in cross-section) with horizontal axis. The two ends of this cylinder 41, provided flanges, are sealed with removable waterproof covers 42.
  • the treatment cells are connected laterally to the cylinder 41 and lie in the same horizontal plane.
  • two heat treatment cells 43 and 44 for example example intended to contain two charges to be cemented, are arranged one opposite the other and are connected to a first box 41-1 transfer component of cylinder 41.
  • a cell loading 45 is arranged opposite a quenching cell 46, these cells being connected to a second transfer case 41-2, itself axially connected to the box 41-1.
  • a handling device is in the form of a carriage 48 moving parallel to the axis of the cylinder 41, from one transfer case to another.
  • This carriage moves, by example, on rails 50 extending all along the cylinder 41.
  • the carriage is provided with a telescopic fork 52 capable of stretch on both sides of the carriage 48 to the center of each cells 43 to 46 to pick up and drop off a charge 54 in process.
  • the carriage 48 is located at cells 45 and 46, and the fork telescopic 52 enters cell 45 to take a load 54.
  • cell 45 has been previously set to the low pressure of enclosure 41 to be able to open the door 45-1 which constitutes, with the exterior door 45-2, an entry airlock.
  • the carriage 48 is at the level of the cells 43 and 44.
  • the installation in FIG. 2 is modular, i.e. one or more additional modules 60 each consisting of a 41-3 transfer case provided with rails 50 'and one or two cells 43' can be connected axially to one of the 41-1 or 41-2 boxes to complete the cylinder 41.
  • the cells 43, 43 'and 44 are cementation cells heated to compliant gases as described above.
  • gas burners are used even in the cementation cells where we are content maintain temperature.
  • An advantage of dissociating the preheating and temperature maintenance functions is that the burners can now be dedicated to only one of the two functions while operating at maximum efficiency.
  • the burners are then controlled to power fixed (for example, at maximum power) and, at least in cementation cells, by clocked regulation.
  • preheating cells in front be provided in a modular cementation plant itself depends on the number of carburizing cells at distribute.
  • provision will be made a preheating cell with a first gas burners power type and carburizing cells with gas burners of a second type of power.
  • We can however use cells using burners double flow gas as previously described in relation to Figure 1, whether for the preheating cell or for cementation cells.
  • Such an embodiment allows optimize temperature regulation and homogeneity in load.
  • the present invention is capable of various variants and modifications which will appear to the man of art.
  • the positioning of the gas burners in a carburizing cell or in a preheating cell in function of the constitution of the cell itself is within reach skilled in the art from functional indications above data and application.
  • the system of control (circuit 20, PLC 30 and valves 21) can be realized using known means.
  • the choice of flow rates gas and air in the gas burners used depends on the powers maximum and timed regulation which are related to the application.
  • the invention can also be implemented in a treatment installation of the type described in European patent No. 0 388 333 of the applicant where several vertical processing cells are spread over a waterproof load transfer enclosure. The adaptation of a such installation to a gas preheating cell and cells gas or electric carburizing is within the reach of the skilled person from the indications given in relation with the horizontal installation of figure 3.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Engineering & Computer Science (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Furnace Details (AREA)
  • Gas Burners (AREA)
  • Air Bags (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Tunnel Furnaces (AREA)
  • Resistance Heating (AREA)

Abstract

Cell for the heat treatment of steel components at low pressure comprises a heating system (1) made up of radiant gas fired tubes distributed around a useful volume of an airtight enclosure and a control system (2) provided with at least one mode of regulation by impulses of the heating system. An Independent claim is included for an installation for the low pressure heat treatment of steel components incorporating several of these cells.

Description

La présente invention concerne le traitement de pièces en acier, et plus précisément le traitement thermique de cémentation, c'est-à-dire d'introduction de carbone dans la surface des pièces pour en améliorer la dureté. L'invention concerne plus particulièrement les installations de cémentation sous vide ou sous faible pression (inférieure à la pression atmosphérique).The present invention relates to the treatment of parts steel, and more precisely the carburizing heat treatment, i.e. introduction of carbon into the surface parts to improve its hardness. The invention relates more particularly vacuum cementation plants or under low pressure (below atmospheric pressure).

Un traitement de cémentation à faible pression consiste à soumettre les pièces à traiter, dans une enceinte étanche à l'air, à une alternance d'étapes d'enrichissement en présence d'un gaz de cémentation à faible pression et d'étapes de diffusion sous vide ou sous atmosphère neutre à faible pression. Les durées respectives des étapes d'enrichissement et de diffusion ainsi que leur nombre dépendent notamment de la concentration en carbone et de la profondeur de cémentation souhaitée dans les pièces, et ces traitements sont bien connus de la technique. Un exemple de procédé de cémentation à basse pression est décrit dans la demande de brevet français N° 2 678 287 de la demanderesse. Tout traitement de cémentation est un traitement thermique à haute température (généralement, de l'ordre de 800 à 1000°C, voire plus) et le chauffage ainsi que le maintien en température homogène des pièces lors des étapes de diffusion et d'enrichissement constituent un point clé des procédés de cémentation. A low pressure carburizing treatment consists of to submit the parts to be treated, in a sealed enclosure to the air, alternating enrichment stages in the presence a low pressure carburizing gas and diffusion steps vacuum or neutral atmosphere at low pressure. The respective durations of enrichment and dissemination stages as well as their number depend in particular on the concentration in carbon and the desired cementation depth in the parts, and these treatments are well known in the art. A example of low pressure carburizing process is described in French patent application No. 2,678,287 of the applicant. Any case hardening treatment is a heat treatment at high temperature (generally, of the order of 800 to 1000 ° C, or more) and heating as well as maintaining the temperature homogeneous parts during the diffusion and enrichment stages constitute a key point in the case hardening processes.

L'invention se réfère également à la carbonitruration dont la seule différence par rapport à la cémentation vient du gaz d'enrichissement utilisé auquel on ajoute généralement de l'ammoniac. Le résultat est la formation de nitrure (au lieu de carbure pour la cémentation) en surface de la pièce. On notera donc que tout ce qui sera exposé par la suite en relation avec la cémentation s'applique également à la carbonitruration.The invention also refers to carbonitriding whose only difference compared to the case hardening comes from enrichment gas used to which is generally added ammonia. The result is the formation of nitride (instead of carbide for cementation) on the surface of the part. We will note so that everything that will be exposed later in relation to the carburizing also applies to carbonitriding.

Généralement, les enceintes de cémentation définissent des volumes d'un ou plusieurs mètres cubes qui sont chauffés et maintenus à la température de cémentation par des moyens de chauffage électrique. En pratique, on utilise des résistances électriques sous forme de barreaux que l'on répartit en périphérie. du volume de cémentation, c'est-à-dire autour de la chambre de cémentation, en fonction de la répartition thermique souhaitée ainsi que des ponts thermiques liés à la constitution de la chambre.Generally, the carburizing chambers define volumes of one or more cubic meters which are heated and maintained at the carburizing temperature by means of Electric heating. In practice, we use resistors electrical in the form of bars that are distributed around the periphery. the volume of carburizing, that is to say around the chamber cementation, depending on the desired thermal distribution as well as thermal bridges linked to the constitution of the chamber.

Il serait souhaitable de pouvoir disposer d'une autre énergie de chauffage des enceintes de cémentation en lieu et place de l'électricité.It would be desirable to have another heating energy of the carburizing chambers in place and place of electricity.

La première énergie qui vient à l'esprit est le gaz qui constitue une énergie "propre" et peu coûteuse. Toutefois, l'utilisation du gaz dans le chauffage d'enceintes de cémentation pose un grand nombre de problèmes qui ont conduit jusqu'à présent à préférer le chauffage électrique, en particulier pour les installations à faible pression.The first energy that comes to mind is the gas that is "clean" and inexpensive energy. However, the use gas in the heating of cementation chambers a large number of problems that have led so far to prefer electric heating, especially for installations at low pressure.

Un premier problème est lié à la constitution même de brûleurs à gaz, qui doivent chauffer l'espace interne de l'enceinte sans y introduire de fumée de combustion du gaz. A cet égard, la longueur nécessaire des brûleurs en raison des grandes dimensions des enceintes de cémentation constitue un point critique en terme de répartition de la chaleur dans l'enceinte.A first problem is linked to the very constitution of gas burners, which must heat the internal space of the enclosure without introducing gas combustion smoke into it. In this regard, the necessary length of the burners due to the large dimensions of the carburizing chambers is a critical point in terms of heat distribution in the enclosure.

Le type de système à brûleur à gaz qu'il conviendrait d'utiliser correspond, par exemple, au système à brûleur décrit dans la demande de brevet français N° 2 616 520. Ce type de système à brûleur est constitué d'une enveloppe externe étanche et d'un tube foyer central délimitant une chambre de combustion. Un tel système utilise une recirculation des gaz brûlés et permet une sortie à grande vitesse de ces gaz. Ce système de brûleur peut le cas échéant être associé à un tube interne du type décrit dans la demande de brevet français N° 2 616 518. Les contenus respectifs des publications susmentionnées sont considérés comme connus.The type of gas burner system that would be suitable to use corresponds, for example, to the burner system described in French patent application No. 2,616,520. This type of system with burner consists of a sealed outer casing and a central hearth tube defining a combustion chamber. A such a system uses a recirculation of the burnt gases and allows a high speed output of these gases. This burner system can if necessary be associated with an internal tube of the type described in French patent application No. 2,616,518. The contents respective of the above publications are considered known.

Un autre problème lié à l'utilisation de tubes à gaz pour le chauffage d'une enceinte de cémentation, en particulier à faible pression, est lié à l'encombrement de ces tubes qui est sensiblement plus important que l'encombrement de barreaux résistifs électriques. Cet encombrement va à l'encontre d'une répartition adéquate de tubes à gaz dans la périphérie du volume utile de l'enceinte pour obtenir une répartition homogène de la température.Another problem related to the use of gas tubes for heating a cementation enclosure, in particular at low pressure, is related to the size of these tubes which is significantly larger than the size of resistive bars electric. This clutter goes against a distribution adequate gas tubes in the periphery of the usable volume of the enclosure to obtain a homogeneous distribution of the temperature.

Un autre problème réside dans la régulation nécessaire de la puissance thermique de la source de chauffage utilisée. En effet, le lot de pièces à cémenter doit tout d'abord être porté à une température élevée de cémentation. Puis, cette température doit être maintenue de façon homogène pendant les traitements liés à la cémentation. Dans un système électrique, la régulation de la température est particulièrement aisée à réaliser par modulation du courant dans les éléments chauffants. Une telle solution n'est pas transposable à des brûleurs à gaz.Another problem is the necessary regulation the thermal power of the heating source used. In Indeed, the batch of pieces to be cemented must first be brought to a high carburizing temperature. Then, this temperature must be maintained homogeneously during treatments related to case hardening. In an electrical system, regulation temperature is particularly easy to achieve by modulation current in the heating elements. Such a solution cannot be transferred to gas burners.

Un objet de la présente invention est de proposer une cellule de cémentation chauffée au gaz qui pallie les inconvénients susmentionnés.An object of the present invention is to provide a gas-heated cementation cell which overcomes the disadvantages mentioned above.

Un autre objet de la présente invention est de proposer une solution qui soit compatible avec la répartition actuelle des moyens de chauffage en périphérie d'une cellule de cémentation.Another object of the present invention is to provide a solution that is compatible with the current distribution of heating means at the periphery of a cementation cell.

Un autre objet de la présente invention est de proposer une installation de cémentation modulaire qui tire profit de l'utilisation du gaz en tant que source d'énergie de chauffage.Another object of the present invention is to provide a modular cementation system which takes advantage of the use of gas as a source of heating energy.

Pour atteindre ces objets, la présente invention prévoit une cellule de traitement thermique à faible pression de pièces d'acier, comportant des moyens de chauffage constitués de plusieurs tubes radiants au gaz répartis autour d'un volume utile d'une enceinte étanche ; et des moyens de commande pourvus au moins d'un mode de régulation par impulsions des moyens de chauffage.To achieve these objects, the present invention provides a low pressure heat treatment cell of steel parts, comprising heating means consisting of several gas radiant tubes distributed around a useful volume a sealed enclosure; and control means provided with the less than one pulse control mode of the heating means.

Selon un mode de réalisation de la présente invention, les moyens de commande sont propres à commander les moyens de chauffage selon deux phases de fonctionnement respectivement de préchauffage à pleine puissance et de maintien en température en régulation par impulsions.According to an embodiment of the present invention, the control means are suitable for controlling the means of heating according to two operating phases respectively of preheating at full power and maintaining temperature in pulse regulation.

Selon un mode de réalisation de la présente invention, les moyens de commande sont propres à modifier le débit de gaz entre deux niveaux respectivement maximum pour le préchauffage et intermédiaire pour la régulation par impulsions.According to an embodiment of the present invention, the control means are suitable for modifying the gas flow rate between two levels respectively maximum for preheating and intermediate for pulse regulation.

Selon un mode de réalisation de la présente invention, tous les tubes radiants au gaz sont commandés individuellement ou par groupes.According to an embodiment of the present invention, all gas radiant tubes are ordered individually or by groups.

Selon un mode de réalisation de la présente invention, les moyens de commande comportent un automate programmable pour individualiser des commandes à destination des différents tubes.According to an embodiment of the present invention, the control means include a programmable controller for individualize orders for the different tubes.

La présente invention prévoit aussi une installation de traitement thermique sous faible pression de pièces d'acier comprenant plusieurs cellules de traitement reliées à une enceinte étanche commune munie de moyens de manutention pour transférer une charge d'une cellule à une autre, au moins une cellule étant du type susmentionné.The present invention also provides an installation for low pressure heat treatment of steel parts comprising several treatment cells connected to an enclosure watertight joint provided with handling means for transferring a charge from one cell to another, at least one cell being of the aforementioned type.

Selon un mode de réalisation de la présente invention, au moins une cellule est dédiée au préchauffage d'une charge à cémenter, et au moins une cellule est une cellule de cémentation.According to an embodiment of the present invention, at least one cell is dedicated to preheating a load to case, and at least one cell is a case cell.

Selon un mode de réalisation de la présente invention, la cellule de cémentation est pourvue de moyens de chauffage au gaz propres à être commandés en mode de régulation par impulsions.According to an embodiment of the present invention, the cementation cell is provided with heating means gases suitable for being controlled in pulse control mode.

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

  • la figure 1 est une vue schématique partiellement en coupe d'un mode de réalisation d'un système de brûleur à gaz dans une cellule de traitement thermique selon la présente invention ;
  • la figure 2 illustre, sous forme de chronogrammes, un mode de mise en oeuvre d'un procédé de commande de brûleurs à gaz selon la présente invention ; et
  • la figure 3 représente, de façon très schématique, un mode de réalisation d'une installation modulaire de traitement thermique mettant en oeuvre la présente invention.
    • These objects, characteristics and advantages, as well as others of the present invention will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:
  • Figure 1 is a schematic partially sectional view of an embodiment of a gas burner system in a heat treatment cell according to the present invention;
  • FIG. 2 illustrates, in the form of timing diagrams, an embodiment of a method for controlling gas burners according to the present invention; and
  • FIG. 3 very schematically shows an embodiment of a modular heat treatment installation implementing the present invention.

    • Pour des raisons de clarté, les chronogrammes de la figure 2 ne sont pas à l'échelle. De plus, seuls les éléments nécessaires à la compréhension de l'invention ont été représentés et seront décrits par la suite. En particulier, en figure 3, on s'est contenté de représenter la structure multicellulaire d'une installation sans se préoccuper des détails constitutifs des cellules qui, sauf précision contraire, sont classiques.For reasons of clarity, the timing diagrams in the figure 2 are not to scale. In addition, only the elements necessary for understanding the invention have been shown and will be described later. In particular, in Figure 3, we simply represented the multicellular structure of a installation without worrying about the details of the cells which, unless otherwise specified, are classic.

    Une caractéristique de la présente invention est de prévoir une commande impulsionnelle de brûleurs à gaz d'une cellule de traitement thermique, au moins pendant des phases de maintien en température après une phase de préchauffe. Ainsi, selon l'invention, on utilise des brûleurs à gaz du type de ceux décrits dans la demande de brevet français N° 2 616 520 susmentionnée, et on commande ces brûleurs de façon à obtenir, au moins après une phase de préchauffe, une régulation cadencée.A feature of the present invention is provide impulse control of gas burners in a cell heat treatment, at least during temperature maintenance after a preheating phase. So according to the invention, gas burners of the type used are used described in the aforementioned French patent application No. 2,616,520, and we control these burners so as to obtain, at least after a preheating phase, timed regulation.

    On aurait pu penser moduler le débit de gaz du brûleur pour adapter la puissance afin d'obtenir la régulation. Toutefois, une telle solution poserait, à faible débit de gaz, des problèmes d'évacuation des fumées dans le brûleur. En effet, les brûleurs sont généralement adaptés pour une évacuation optimale des fumées dans une certaine plage de débits et un fonctionnement sous très faible débit de gaz ne permet ni d'obtenir une répartition homogène de la température dans le tube, ni d'obtenir une récupération correcte d'énergie des fumées. En outre, cela peut poser des problèmes de stabilité de la flamme.One would have thought to modulate the gas flow rate of the burner to adapt the power in order to obtain regulation. However, such a solution would pose, at low gas flow, smoke evacuation problems in the burner. Indeed, the burners are generally suitable for optimal evacuation fumes in a certain range of flow rates and operation under very low gas flow neither allows to obtain a distribution homogeneous temperature in the tube, nor to obtain a correct recovery of smoke energy. In addition, this can pose flame stability issues.

    De préférence, pour améliorer l'homogénéité de la puissance de chauffage du tube, on effectue selon l'invention une commutation entre deux débits d'air et de gaz selon le mode de fonctionnement du brûleur. Ainsi, on prévoit des brûleurs dits à deux débits d'air et de gaz permettant un fonctionnement dans un premier débit maximal pour une phase de préchauffe et un fonctionnement dans un deuxième débit intermédiaire pour la phase de régulation. Selon l'invention, le débit intermédiaire ne correspond pas au débit minimal du brûleur, de sorte que les deux débits permettent une homogénéité acceptable de la température, avec une récupération correcte des fumées dans le brûleur.Preferably, to improve the homogeneity of the power tube heating, is carried out according to the invention a switching between two air and gas flows according to the mode of burner operation. Thus, so-called burners are provided. two air and gas flows allowing operation in a first maximum flow for a preheating phase and a operation in a second intermediate flow for the phase of regulation. According to the invention, the intermediate flow does not does not correspond to the minimum burner flow rate, so that both flow rates allow acceptable temperature uniformity, with correct recovery of the fumes in the burner.

    La figure 1 représente un mode de réalisation de la présente invention. Cette figure illustre, très partiellement, une cellule de traitement thermique en ce qu'elle représente un unique brûleur à gaz 1 ainsi que le système 2 de commande des brûleurs à gaz de la cellule.FIG. 1 represents an embodiment of the present invention. This figure illustrates, very partially, a heat treatment cell in that it represents a single gas burner 1 as well as the system 2 for controlling cell gas burners.

    Le brûleur à gaz 1 est essentiellement constitué d'une enveloppe radiante externe 10 en forme de doigt de gant qui traverse, par l'intermédiaire d'un système d'étanchéité au vide 11, la paroi 12 de la cellule de traitement. Le brûleur comporte également un tube 13, interne à l'enveloppe 10 et coaxial à celle-ci. Une première extrémité du tube 13 est voisine de l'extrémité de l'enveloppe 10 dans la cellule de cémentation. Une deuxième extrémité du tube 13 est ouverte en direction d'une sortie d'une chambre 14 destinée à réaliser le mélange gaz-air du brûleur et la combustion. Comme l'illustre des flèches en figure 1, le brûleur est de préférence à recirculation des fumées, c'est-à-dire qu'une partie des fumées de combustion est utilisée pour être réintroduite en entrée du tube 13, le reste des fumées étant évacué par un évent 15 de l'enveloppe 10 à l'extérieur de la cellule. Pour des raisons de clarté, le brûleur a été représenté de façon très schématique et, en particulier, les moyens d'allumage de la flamme n'ont pas été illustrés. La chambre 14 comporte au moins une arrivée 16 de gaz et au moins une arrivée 17 d'air. Généralement, plusieurs arrivées d'air sont prévues pour mieux homogénéiser le mélange gaz-air à brûler. Les conduits 16 et 17 d'amenée d'air sortent de l'enveloppe 10 à l'extérieur de la cellule de cémentation.The gas burner 1 essentially consists of a external radiant envelope 10 in the form of a glove which passes through, by means of a vacuum sealing system 11, the wall 12 of the treatment cell. The burner has also a tube 13, internal to the casing 10 and coaxial with this one. A first end of the tube 13 is close to the end of the casing 10 in the carburizing cell. A second end of tube 13 is open towards an outlet a chamber 14 intended to produce the gas-air mixture of burner and combustion. As illustrated by the arrows in the figure 1, the burner is preferably recirculating the fumes, that is to say that part of the combustion fumes is used to be reintroduced at the inlet of tube 13, the rest of the fumes being evacuated by a vent 15 from the envelope 10 outside of the cell. For reasons of clarity, the burner has been shown very schematically and, in particular, the means flame ignition have not been illustrated. Room 14 has at least one gas supply 16 and at least one gas supply 17 air. Generally, several air intakes are planned to better homogenize the gas-air mixture to be burned. The conduits 16 and 17 of air intake exit from the envelope 10 to the outside of the cementation cell.

    De préférence, la position du brûleur 1 par rapport à la paroi de l'enceinte 12 est telle que tout le tube 13 est contenu dans le volume interne de la cellule de cémentation. Toutefois, l'intégralité du tube 13 n'est, de préférence, pas contenue dans le volume dit "chaud" de l'enceinte de cémentation qui est généralement délimité par un écran thermique (symbolisé par un pointillé 18). De même la chambre 14 elle-même se trouve dans le volume interne de la cellule, mais préférentiellement hors du volume chaud. La position du brûleur 1 est choisie pour que la partie du tube 13 dans le volume chaud soit homogène en température. Dans un mode de mise en oeuvre de l'invention, l'adaptation de la position du brûleur s'effectue en déplaçant l'intégralité de celui-ci (enveloppe 10 comprise) par rapport à la paroi 12 de l'enceinte, pour régler la position de l'entrée du tube 13 par rapport à l'écran thermique 18.Preferably, the position of the burner 1 relative to the wall of the enclosure 12 is such that the entire tube 13 is contained in the internal volume of the cementation cell. However, the entire tube 13 is preferably not contained in the so-called "hot" volume of the cementation enclosure which is generally delimited by a heat shield (symbolized with a dotted line 18). Likewise room 14 itself is in the internal volume of the cell, but preferably out of the hot volume. The position of burner 1 is chosen for that the part of the tube 13 in the hot volume is homogeneous in temperature. In one embodiment of the invention, the position of the burner is adjusted by moving all of it (including envelope 10) compared to the wall 12 of the enclosure, to adjust the position of the inlet of the tube 13 relative to the heat shield 18.

    De préférence, tous les brûleurs à gaz de la cellule de traitement thermique sont commandés par un même système 2 de régulation. Le système 2 comporte essentiellement un circuit électronique (REG) de régulation 20 (en pratique, un ou plusieurs circuits) et un réseau 21 de vannes commandées par le circuit 20, le cas échéant par l'intermédiaire d'un automate programmable 30 (AUTO) comme on le verra par la suite. Pour assurer la fonction de régulation, le circuit 20 reçoit des signaux 22 de mesure et de commande. Les signaux de mesure sont essentiellement constitués de résultats de mesure fournis par au moins un capteur de température de l'enceinte de cémentation. Les signaux de commande proviennent d'une centrale de commande accessible par l'opérateur. Le circuit 20 de régulation (ou l'automate 30) délivre des signaux 23 de commande à destination des brûleurs à gaz pour allumer et éteindre leurs flammes respectives. Preferably, all the gas burners in the fuel cell heat treatment are controlled by the same system 2 of regulation. System 2 essentially comprises a circuit electronic regulation (REG) 20 (in practice, one or more circuits) and a network 21 of valves controlled by circuit 20, if necessary via a programmable controller 30 (AUTO) as we will see later. To perform the function control, circuit 20 receives measurement signals 22 and control. The measurement signals are essentially made up measurement results supplied by at least one temperature of the carburizing chamber. Control signals come from a control center accessible by the operator. The regulation circuit 20 (or the automaton 30) delivers control signals 23 to the gas burners for ignite and extinguish their respective flames.

    Selon la présente invention, le circuit 20 commande également le réseau 21 de vannes de gaz et d'air. Ce réseau de vannes sert à commander les débits de gaz et d'air respectifs des différents brûleurs.According to the present invention, the circuit 20 controls also the network 21 of gas and air valves. This network of valves is used to control the respective gas and air flow rates of the different burners.

    Pour simplifier la figure 1, les conduits de gaz et d'air ont été représentés de façon unifilaire dans le réseau de vannes 21. On notera que la structure de vannes illustrée par la figure 1 est, de préférence, reproduite pour chaque brûleur.To simplify Figure 1, the gas pipes and were represented in a single line in the network of valves 21. Note that the valve structure illustrated by the Figure 1 is preferably reproduced for each burner.

    Dans le mode de réalisation pris pour exemple en figure 1, une conduite principale 24 d'amenée de gaz est répartie en deux conduites 25 et 26 respectivement associées à des limiteurs de débit 25-1 et 26-1. Les conduites 25 et 26 ont, selon l'invention, des débits différents. Par exemple, la conduite 25 est destinée à fournir, en association avec le limiteur 25-1, un débit de gaz maximal pour le fonctionnement du brûleur en puissance maximale pendant au moins une phase de préchauffe. La conduite 26 est destinée à fournir, en association avec le limiteur 26-1, un débit de gaz inférieur pour le fonctionnement du brûleur dans le régime cadencé de l'invention. Côté circuit d'air, une conduite principale 27 est divisée en deux conduites 28 et 29 respectivement associées à des limiteurs 28-1 et 29-1 dont les rôles sont similaires à ceux exposés ci-dessus en relation avec l'alimentation en gaz. De préférence, les débits imposés par les limiteurs 25-1, 26-1, 28-1 et 29-1 sont préréglés.In the embodiment taken as an example in the figure 1, a main gas supply pipe 24 is divided into two pipes 25 and 26 respectively associated with limiters 25-1 and 26-1. The lines 25 and 26 have, according to the invention, different bit rates. For example, line 25 is intended to supply, in association with the limiter 25-1, a flow maximum gas for burner operation in power maximum during at least one preheating phase. Driving 26 is intended to provide, in association with the limiter 26-1, a lower gas flow rate for burner operation in the timed scheme of the invention. On the air circuit side, a pipe main 27 is divided into two pipes 28 and 29 respectively associated with limiters 28-1 and 29-1 whose roles are similar to those exposed above in relation to food in gas. Preferably, the flow rates imposed by the limiters 25-1, 26-1, 28-1 and 29-1 are preset.

    Selon l'invention, chacune des conduites 25, 26, 28 et 29 est associée à une vanne 25-2, 26-2, 28-2 et 29-2 de commande en tout ou rien. Les vannes 26-2 et 29-2 sont, de préférence, commandées simultanément par un signal 32 délivré par le circuit 20 (ou par l'automate 30) en régime cadencé. Les vannes 25-2 et 28-2 sont, de préférence, commandées simultanément par un signal 33 issu du circuit 20 ou de l'automate 30. Les extrémités des conduites 25, 26 et 28, 29 sont réunies à leurs extrémités opposées respectives.According to the invention, each of the pipes 25, 26, 28 and 29 is associated with a control valve 25-2, 26-2, 28-2 and 29-2 in all or nothing. Valves 26-2 and 29-2 are preferably simultaneously controlled by a signal 32 delivered by the circuit 20 (or by the automaton 30) in clocked mode. Valves 25-2 and 28-2 are preferably controlled simultaneously by a signal 33 from circuit 20 or from automaton 30. The ends of the pipes 25, 26 and 28, 29 are joined at their opposite ends respective.

    Le fonctionnement d'un système de brûleurs à gaz selon l'invention sera exposé par la suite en relation avec la figure 2 qui représente, sous forme de chronogrammes, un exemple d'allure du signal 33, du signal 32 et de la puissance instantanée P correspondante des brûleurs à gaz.The operation of a gas burner system according to the invention will be explained below in relation to FIG. 2 which represents, in the form of chronograms, an example of pace signal 33, signal 32 and instantaneous power P gas burners.

    Selon le mode de mise en oeuvre illustré par la figure 2, on commence, dans une phase de préchauffe (instant t0 à t1), par utiliser le brûleur à puissance maximale, c'est-à-dire au débit de gaz et d'air le plus fort. Dans cette phase de préchauffe, les vannes 25-2 et 28-2 sont ouvertes au débit maximum. Le cas échéant, on peut prévoir que le débit maximum soit fixé par la somme des débits de tous les limiteurs. Dans ce cas, les vannes 26-2 et 29-2 sont également ouvertes. Puis, on prévoit, de préférence, une phase intermédiaire (instant t1 à t2) pendant laquelle la puissance du brûleur passe sur le débit inférieur sans cadencement. Pour ce faire, à partir de l'instant t1, le brûleur 1 fonctionne en régime de puissance intermédiaire. Par conséquent, le signal 33 de commande change d'état afin de fermer les vannes 25-2 et 28-2 et le signal 32 change d'état pour ouvrir (si elles ne le sont pas déjà) les vannes 26-2 et 29-2. L'instant t1 est fixé par l'approche d'une consigne de température inférieure à la température de régulation souhaitée. La phase intermédiaire entre les instants t1 et t2 peut, en particulier, servir à éviter le dépassement de la consigne de température en raison de l'inertie du système.According to the mode of implementation illustrated by the figure 2, we start, in a preheating phase (time t0 to t1), by using the burner at maximum power, i.e. at the rate strongest gas and air. In this preheating phase, valves 25-2 and 28-2 are open at maximum flow. The case if necessary, provision may be made for the maximum flow rate to be fixed by the sum of the flow rates of all limiters. In this case, the valves 26-2 and 29-2 are also open. Then, preferably, provision is made, an intermediate phase (instant t1 to t2) during which the burner power goes to the lower flow without timing. To do this, from time t1, the burner 1 operates in intermediate power regime. Therefore, the control signal 33 changes state in order to close the valves 25-2 and 28-2 and signal 32 changes state to open (if they are not already) valves 26-2 and 29-2. The instant t1 is set by approaching a temperature setpoint below the desired control temperature. The intermediate phase between times t1 and t2 can, in particular, be used to avoid the temperature setpoint exceeded due to inertia of the system.

    A partir de l'instant t2, on effectue une régulation de maintien en température de l'enceinte de cémentation. A partir de cet instant, le signal 32 de régulation cadencée adapte, en fonction des paramètres que reçoit le circuit 20 par les signaux 22, les durées respectives d'ouverture des vannes 26-2 et 29-2. Dans l'exemple illustré par la figure 2, on suppose que, entre des instants t2 et t3, la puissance souhaitée pour le brûleur est relativement importante et nécessite des impulsions de durée relativement longue. Il peut s'agir, par exemple, d'une phase d'adaptation du changement de puissance du brûleur entre ses niveaux maximum et intermédiaire. A partir de l'instant t3, on peut considérer que l'on se trouve dans une phase de régulation proprement dite où le rapport cyclique des impulsions d'allumage du brûleur dépend exclusivement des variations de température dans la chambre de cémentation. Ces variations peuvent provenir, par exemple, d'une modification imposée par le procédé de cémentation ou d'un transfert de charge dans la cellule. En figure 2, on a illustré un besoin de diminution de puissance à partir d'un instant t4.From time t2, we regulate temperature maintenance of the cementation enclosure. From at this instant, the clocked regulation signal 32 adapts, in function of the parameters that the circuit 20 receives by the signals 22, the respective opening times of valves 26-2 and 29-2. In the example illustrated by Figure 2, we assume that between at times t2 and t3, the desired power for the burner is relatively large and requires pulses of duration relatively long. It can be, for example, a phase adaptation of the burner power change between its maximum and intermediate levels. From time t3, we can consider that we are in a regulatory phase proper where the duty cycle of the ignition pulses of the burner depends exclusively on temperature variations in the carburizing chamber. These variations can come from, for example, of a modification imposed by the process of carburizing or charge transfer in the cell. In Figure 2, we illustrated a need to decrease power to from an instant t4.

    On notera que les temps d'allumage et les temps d'arrêt respectifs des brûleurs sont établis, entre autres, en fonction de la disposition des brûleurs dans l'enceinte et de leur constitution.Note that the ignition times and the stop times respective burners are established, among other things, according to the arrangement of the burners in the enclosure and their constitution.

    A titre de variante, les brûleurs peuvent être commandés en régime cadencé même lors de leur fonctionnement en pleine puissance.Alternatively, the burners can be ordered in clocked mode even during their operation in full power.

    Bien qu'il soit possible de prévoir une excitation simultanée de tous les brûleurs de l'enceinte, on préfère individualiser les commandes des différents brûleurs de la cellule de cémentation. Par exemple, on pourra prévoir des temps d'allumage plus longs pour des brûleurs situés à proximité de ponts thermiques constitués, par exemple, par les pieds de support de la charge à chauffer. Dans ce cas, l'automate 30 fournit des commandes individuelles (signaux 32' et 33' à destination d'autres brûleurs non représentés), par exemple en différant l'allumage des brûleurs successivement et en adaptant les durées des impulsions d'allumage aux différents brûleurs. L'automate 30 a un fonctionnement préétabli et reçoit, entre autres, des signaux 34 et 35 de commande provenant du régulateur et qui sont communs à tous les brûleurs, l'automate se chargeant d'adapter ces signaux aux différents brûleurs.Although it is possible to predict an excitement simultaneous of all the burners of the enclosure, we prefer to individualize the controls of the different burners of the case hardening. For example, we could plan ignition times longer for burners located near thermal bridges formed, for example, by the support feet of the charge to be heated. In this case, the controller 30 provides individual commands (signals 32 'and 33' to destination other burners not shown), for example by differing igniting the burners successively and adjusting the times ignition pulses to the different burners. The automaton 30 has a pre-established functioning and receives, among other things, control signals 34 and 35 from the regulator which are common to all burners, the automaton taking charge of adapting these signals to the different burners.

    A cet égard, on notera que les différents brûleurs seront répartis dans la cellule de cémentation en fonction de l'homogénéité thermique souhaitée. Par exemple, on pourra souhaiter disposer en bas de la cellule de cémentation, c'est-à-dire au voisinage des pieds supportant la charge, d'une puissance plus forte à cadence égale ou d'un temps de chauffe plus long afin d'améliorer l'homogénéité verticale. Dans la direction longitudinale de la cellule (dans le sens longitudinal des brûleurs), les ajustements d'homogénéité dépendent essentiellement du choix de la puissance intermédiaire qui est fonction de la longueur des brûleurs, donc du volume de l'enceinte.In this regard, it will be noted that the different burners will be distributed in the cementation cell according to the desired thermal uniformity. For example, we may wish have at the bottom of the cementation cell, i.e. at the vicinity of the feet supporting the load, more powerful strong at equal rate or a longer heating time so to improve vertical homogeneity. In the longitudinal direction of the cell (in the longitudinal direction of the burners), the homogeneity adjustments essentially depend on the choice of the intermediate power which is a function of the length of burners, therefore the volume of the enclosure.

    En variante, les brûleurs pourront être commandés par groupes.Alternatively, the burners may be controlled by groups.

    La figure 3 illustre un exemple d'application de la présente invention à une installation modulaire de cellules de cémentation. Le mode de réalisation de la figure 3 s'inspire d'une installation modulaire telle que décrite dans la demande de brevet européen N° 0 922 778 de la demanderesse que l'on considère comme connue.Figure 3 illustrates an example of application of the present invention to a modular installation of cells case hardening. The embodiment of Figure 3 is inspired a modular installation as described in the request for European patent N ° 0 922 778 of the applicant that we consider as known.

    Un module de base 40 comprend une enceinte étanche 41 sous forme de cylindre (de section non nécessairement circulaire) à axe horizontal. Les deux extrémités de ce cylindre 41, munies de collerettes, sont bouchées par des couvercles étanches amovibles 42. Les cellules de traitement sont reliées latéralement au cylindre 41 et se trouvent dans un même plan horizontal. Par exemple, deux cellules de traitement thermique 43 et 44, par exemple destinées à contenir deux charges à cémenter, sont disposées l'une en face de l'autre et sont reliées à un premier caisson de transfert 41-1 constitutif du cylindre 41. Une cellule de chargement 45 est disposée en face d'une cellule de trempe 46, ces cellules étant reliées à un deuxième caisson de transfert 41-2, lui-même relié axialement au caisson 41-1.A basic module 40 includes a sealed enclosure 41 in the form of a cylinder (not necessarily circular in cross-section) with horizontal axis. The two ends of this cylinder 41, provided flanges, are sealed with removable waterproof covers 42. The treatment cells are connected laterally to the cylinder 41 and lie in the same horizontal plane. Through example, two heat treatment cells 43 and 44, for example example intended to contain two charges to be cemented, are arranged one opposite the other and are connected to a first box 41-1 transfer component of cylinder 41. A cell loading 45 is arranged opposite a quenching cell 46, these cells being connected to a second transfer case 41-2, itself axially connected to the box 41-1.

    Un dispositif de manutention est sous la forme d'un chariot 48 se déplaçant parallèlement à l'axe du cylindre 41, d'un caisson de transfert à un autre. Ce chariot se déplace, par exemple, sur des rails 50 s'étendant tout le long du cylindre 41. Le chariot est muni d'une fourche télescopique 52 susceptible de s'étirer de part et d'autre du chariot 48 jusqu'au centre de chacune des cellules 43 à 46 pour y prendre et y déposer une charge 54 en cours de traitement. A la figure 3, en traits pleins, le chariot 48 se trouve au niveau des cellules 45 et 46, et la fourche télescopique 52 pénètre dans la cellule 45 pour y prendre une charge 54. Bien entendu, la cellule 45 a été préalablement mise à la basse pression de l'enceinte 41 pour pouvoir ouvrir la porte 45-1 qui constitue, avec la porte extérieure 45-2, un sas d'entrée. En pointillés, le chariot 48 se trouve au niveau des cellules 43 et 44. L'installation de la figure 2 est modulaire, c'est-à-dire qu'un ou plusieurs modules supplémentaires 60 constitués chacun d'un caisson de transfert 41-3 pourvu de rails 50' et d'une ou deux cellules 43' peuvent être raccordés axialement à l'un des caissons 41-1 ou 41-2 pour compléter le cylindre 41.A handling device is in the form of a carriage 48 moving parallel to the axis of the cylinder 41, from one transfer case to another. This carriage moves, by example, on rails 50 extending all along the cylinder 41. The carriage is provided with a telescopic fork 52 capable of stretch on both sides of the carriage 48 to the center of each cells 43 to 46 to pick up and drop off a charge 54 in process. In Figure 3, in solid lines, the carriage 48 is located at cells 45 and 46, and the fork telescopic 52 enters cell 45 to take a load 54. Of course, cell 45 has been previously set to the low pressure of enclosure 41 to be able to open the door 45-1 which constitutes, with the exterior door 45-2, an entry airlock. Dotted, the carriage 48 is at the level of the cells 43 and 44. The installation in FIG. 2 is modular, i.e. one or more additional modules 60 each consisting of a 41-3 transfer case provided with rails 50 'and one or two cells 43' can be connected axially to one of the 41-1 or 41-2 boxes to complete the cylinder 41.

    Selon un premier mode d'application de l'invention à une installation modulaire telle que décrite ci-dessus, les cellules 43, 43' et 44 sont des cellules de cémentation chauffées au gaz conformes telles que décrites précédemment.According to a first mode of application of the invention to a modular installation as described above, the cells 43, 43 'and 44 are cementation cells heated to compliant gases as described above.

    Selon un deuxième mode d'application de l'invention à une telle installation modulaire et selon un deuxième aspect de l'invention, on prévoit de dissocier les opérations de préchauffage d'une charge à cémenter des opérations de maintien en température. Pour cela, on affecte une des cellules, par exemple la cellule 44 en figure 3, au préchauffage de toutes les charges à cémenter. Cette cellule est alors équipée de brûleurs à gaz pour porter la charge à cémenter à une température voisine de la température de travail, par exemple, à une température comprise entre 600 et 800°C. Par la suite, les charges sont transférées vers les autres cellules de cémentation 43 et 43' dans lesquelles la seule opération de chauffe nécessaire est destinée au maintien et à l'homogénéisation de la température des différentes pièces. Par conséquent, on optimise l'utilisation des moyens de chauffage. Les moyens utilisés dans les cellules de cémentation 43 et 43' peuvent rester électriques alors que ceux de la cellule de préchauffage 44 sont à gaz. Toutefois, selon un mode de réalisation préféré de l'invention, on utilise des brûleurs à gaz même dans les cellules de cémentation où on se contente d'effectuer un maintien en température. Dans ce cas, on pourra prévoir une cellule de préchauffe utilisant des brûleurs d'un premier type et des cellules de cémentation utilisant des brûleurs d'un deuxième type moins puissants que les premiers, ou les mêmes brûleurs mais à moindre débit. Un avantage de dissocier les fonctions de préchauffage et de maintien en température est que les brûleurs peuvent désormais être dédiés à une seule des deux fonctions tout en fonctionnant tous à rendement maximum. Ainsi, on peut se dispenser de la structure à double débit de gaz en prévoyant deux types de brûleurs, sans rencontrer ici de problèmes d'encombrement. Les brûleurs sont alors commandés à puissance fixe (par exemple, à puissance maximale) et, au moins dans les cellules de cémentation, par régulation cadencée.According to a second mode of application of the invention to such a modular installation and according to a second aspect of the invention, it is planned to separate the preheating operations of a charge to be cemented for temperature maintenance operations. For this, we affect one of the cells, for example the cell 44 in FIG. 3, at the preheating of all the loads at cement. This cell is then equipped with gas burners for bring the charge to be cemented to a temperature close to the working temperature, for example, at a temperature between 600 and 800 ° C. Thereafter, the charges are transferred to the other cementation cells 43 and 43 'in which the only heating operation necessary is intended to maintain and the homogenization of the temperature of the different rooms. Consequently, the use of the means of optimization is optimized. heater. The means used in the cementation cells 43 and 43 'can remain electric while those of the cell 44 are gas. However, according to a mode of preferred embodiment of the invention, gas burners are used even in the cementation cells where we are content maintain temperature. In this case, we can provide a preheating cell using burners of a first type and cementation cells using second type burners less powerful than the first, or the same burners but at a lower flow rate. An advantage of dissociating the preheating and temperature maintenance functions is that the burners can now be dedicated to only one of the two functions while operating at maximum efficiency. Thus, we can dispense with the double gas flow structure by providing two types of burners, without encountering problems here of space. The burners are then controlled to power fixed (for example, at maximum power) and, at least in cementation cells, by clocked regulation.

    On notera que le nombre de cellules de préchauffe devant être prévu dans une installation de cémentation modulaire dépend lui-même du nombre de cellules de cémentation à distribuer. Dans un mode de réalisation simplifié, on prévoira une cellule de préchauffe avec des brûleurs à gaz d'un premier type de puissance et des cellules de cémentation avec des brûleurs à gaz d'un deuxième type de puissance. On pourra cependant mettre en oeuvre des cellules ayant recours à des brûleurs à gaz à double débit tels que décrits précédemment en relation avec la figure 1, que ce soit pour la cellule de préchauffe ou pour les cellules de cémentation. Un tel mode de réalisation permet d'optimiser la régulation et l'homogénéité de la température dans la charge.Note that the number of preheating cells in front be provided in a modular cementation plant itself depends on the number of carburizing cells at distribute. In a simplified embodiment, provision will be made a preheating cell with a first gas burners power type and carburizing cells with gas burners of a second type of power. We can however use cells using burners double flow gas as previously described in relation to Figure 1, whether for the preheating cell or for cementation cells. Such an embodiment allows optimize temperature regulation and homogeneity in load.

    Bien entendu, la présente invention est susceptible de diverses variantes et modifications qui apparaítront à l'homme de l'art. En particulier, le positionnement des brûleurs à gaz dans une cellule de cémentation ou dans une cellule de préchauffe en fonction de la constitution de la cellule elle-même est à la portée de l'homme du métier à partir des indications fonctionnelles données ci-dessus et de l'application. De même, le système de commande (circuit 20, automate 30 et vannes 21) peut être réalisé en utilisant des moyens connus. De plus, le choix des débits de gaz et d'air dans les brûleurs à gaz utilisés dépend des puissances maximale et de régulation cadencée qui sont liées à l'application. L'invention peut également être mise en oeuvre dans une installation de traitement du type de celle décrite dans le brevet européen N° 0 388 333 de la demanderesse où plusieurs cellules de traitement verticales sont réparties au-dessus d'une enceinte étanche de transfert de la charge. L'adaptation d'une telle installation à une cellule de préchauffe à gaz et des cellules de cémentation à gaz ou électriques est à la portée de l'homme du métier à partir des indications données en relation avec l'installation horizontale de la figure 3.Of course, the present invention is capable of various variants and modifications which will appear to the man of art. In particular, the positioning of the gas burners in a carburizing cell or in a preheating cell in function of the constitution of the cell itself is within reach skilled in the art from functional indications above data and application. Likewise, the system of control (circuit 20, PLC 30 and valves 21) can be realized using known means. In addition, the choice of flow rates gas and air in the gas burners used depends on the powers maximum and timed regulation which are related to the application. The invention can also be implemented in a treatment installation of the type described in European patent No. 0 388 333 of the applicant where several vertical processing cells are spread over a waterproof load transfer enclosure. The adaptation of a such installation to a gas preheating cell and cells gas or electric carburizing is within the reach of the skilled person from the indications given in relation with the horizontal installation of figure 3.

    Claims (8)

    Cellule (43, 43', 44) de traitement thermique à faible pression de pièces d'acier, caractérisée en ce qu'elle comporte : des moyens de chauffage (1) constitués de plusieurs tubes radiants au gaz répartis autour d'un volume utile d'une enceinte étanche ; et des moyens de commande (2) pourvus au moins d'un mode de régulation par impulsions desdits moyens de chauffage. Low pressure heat treatment cell (43, 43 ', 44) for steel parts, characterized in that it comprises: heating means (1) consisting of several gas radiant tubes distributed around a useful volume of a sealed enclosure; and control means (2) provided with at least one mode of pulse regulation of said heating means. Cellule de traitement thermique selon la revendication 1, caractérisée en ce que les moyens de commande (2) sont propres à commander les moyens de chauffage selon deux phases de fonctionnement respectivement de préchauffage à pleine puissance et de maintien en température en régulation par impulsions.Heat treatment cell according to claim 1, characterized in that the control means (2) are suitable for controlling the heating means according to two operating phases respectively of preheating at full power and of maintaining the temperature in pulse regulation. Cellule de traitement thermique selon la revendication 2, caractérisée en ce que les moyens de commande (2) sont propres à modifier le débit de gaz entre deux niveaux respectivement maximum pour le préchauffage et intermédiaire pour la régulation par impulsions.Heat treatment cell according to claim 2, characterized in that the control means (2) are adapted to modify the gas flow rate between two levels respectively maximum for preheating and intermediate for regulation by pulses. Cellule selon l'une quelconque des revendications 1 à 3, caractérisée en ce que les tubes radiants au gaz (1) sont commandés individuellement ou par groupes.Cell according to any one of claims 1 to 3, characterized in that the gas radiant tubes (1) are controlled individually or in groups. Cellule selon la revendication 4, caractérisée en ce que les moyens de commande comportent un automate programmable pour individualiser des commandes à destination des différents tubes.Cell according to claim 4, characterized in that the control means comprise a programmable automaton for individualizing commands intended for the various tubes. Installation de traitement thermique sous faible pression de pièces d'acier comprenant plusieurs cellules (43, 43', 44', 45, 46) de traitement reliées à une enceinte étanche commune (41), munie de moyens (48, 50, 52) de manutention pour transférer une charge (54) d'une cellule à une autre, caractérisée en ce qu'au moins une cellule (44) est conforme à l'une quelconque des revendications 1 à 5.Installation for heat treatment under low pressure of steel parts comprising several treatment cells (43, 43 ', 44', 45, 46) connected to a common sealed enclosure (41), provided with means (48, 50, 52) handling device for transferring a load (54) from one cell to another, characterized in that at least one cell (44) conforms to any one of claims 1 to 5. Installation selon la revendication 6, caractérisée en ce qu'elle comporte au moins une cellule (44) dédiée au préchauffage d'une charge à cémenter, et au moins une cellule de cémentation (43, 43').Installation according to claim 6, characterized in that it comprises at least one cell (44) dedicated to the preheating of a charge to be cemented, and at least one cementation cell (43, 43 '). Installation selon la revendication 7, caractérisée en ce que ladite cellule de cémentation (43, 43') est pourvue de moyens de chauffage au gaz propres à être commandés en mode de régulation par impulsions.Installation according to claim 7, characterized in that said cementing cell (43, 43 ') is provided with gas heating means suitable for being controlled in pulse regulation mode.
    EP01410062A 2000-06-06 2001-06-05 Gas-heated carburising installation Expired - Lifetime EP1162279B1 (en)

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    FR0007232A FR2809746B1 (en) 2000-06-06 2000-06-06 GAS-HEATED CEMENTATION SYSTEM
    FR0007232 2000-06-06

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    EP1162279B1 EP1162279B1 (en) 2005-08-17

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    AT504218B1 (en) * 2006-10-02 2008-06-15 Siemens Vai Metals Tech Gmbh REEL OVEN
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    MXPA01005661A (en) 2003-10-06
    CA2350004A1 (en) 2001-12-06
    FR2809746A1 (en) 2001-12-07
    FR2809746B1 (en) 2003-03-21
    DE60112657T2 (en) 2006-06-14
    US20020017746A1 (en) 2002-02-14
    CN1328171A (en) 2001-12-26
    EP1162279B1 (en) 2005-08-17
    US6627145B2 (en) 2003-09-30
    ATE302290T1 (en) 2005-09-15
    JP2002146513A (en) 2002-05-22
    DE60112657T9 (en) 2006-10-19
    DE60112657D1 (en) 2005-09-22

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