WO2004033731A1

WO2004033731A1 - Heat treatment method for metal parts

Info

Publication number: WO2004033731A1
Application number: PCT/EP2003/011325
Authority: WO
Inventors: Thierry Sperisen
Original assignee: Patherm Sa
Priority date: 2002-10-11
Filing date: 2003-10-10
Publication date: 2004-04-22
Also published as: AU2003280366A1; FR2845695A1; FR2845695B1

Abstract

The invention concerns a heat treatment method for metal parts (6) arranged in feed (5) wherein the feed of parts is successively brought into a vertical treatment furnace (1) capable of being opened downwards, said method consisting in: closing the furnace with a closure stopper (11) capable of supporting the feed (5), then performing the desired heat treatment provided by the furnace (1), and once said treatment has been carried out, opening the stopper (11). The invention is characterized in that it consists in: generating a treatment gas interface in a vestibule (25) between the opening of the furnace and outside air, bringing one or more parts (6) of the feed (5) horizontally opposite a lateral opening (27) provided in the wall of said vestibule (25), gripping said part(s) (6) from outside through said opening, removing said part(s) from the feed (5) and from the vestibule (25), so that said part(s) located in the corridor (25) are protected from surface modification by the treatment gases therein.

Description

PROCESS FOR THE HEAT TREATMENT OF METAL PARTS

The invention relates to a method and an installation for heat treatment of metal parts, more specifically making it possible to carry out thermochemical treatments and quenching operations in particular in press.

Thermochemical treatments of metals consist in conferring particular mechanical properties (hardness, tribological properties, aspects, etc.) on the surface of the part or on shallow depths by modifying the chemical composition using gas mixtures at temperatures located between 400 ° C and 1200 ° C. These operations take place at variable temperatures depending on the nature of the treatment and the base materials, but are typically between 500 and 1200 ° C.

Heat treatment of metal parts requires rapid cooling operations in order to give the parts mechanical properties in the mass. These quenching or hardening by quenching are generally accompanied by significant geometric deformations due to the thermal gradients, the variation of the heat exchange coefficient between the part and the cooling medium over time and the dimensional variations linked to the modification. of the crystalline structure of the materials. In many cases, the deformations generated during quenching are such that the part must be straightened or resized after treatment. These operations are extremely expensive.

In an attempt to overcome these problems, press quenching operations have been used for a long time, in particular for pinions, by applying external mechanical stress when the part or parts are cooled in order to limit its or their deformation. The part or parts to be quenched in a press are generally removed from the oven either manually or using a robot, and are placed under the press. The passage of the part in the air between the oven and the press is not harmful. These so-called press quenching processes are normally carried out piece by piece or in small groups of pieces in oven installations with parade treatment. The duration of the surface modification treatment (case hardening, nitriding or any other similar process) is several orders of magnitude greater than the press quenching operation which lasts only a few minutes. The method and the installation which is the subject of the present invention relates to a heat treatment of parts arranged under load requiring a thermochemical treatment followed by quenching or cooling under stress (either one by one or in small batches).

Furnaces have long been available for thermochemical treatments and for removing parts from the oven to bring them under a press for hardening under stress. These ovens are generally parade ovens fitted with a heating tunnel, of the "pushing" type or fitted with a roller hearth for driving the parts. These ovens have two very important disadvantages. On the one hand, the durations of the thermochemical treatments being typically of the order of several hours, these ovens are very long and very bulky, therefore very costly in terms of investment, surface area used and production costs.

On the other hand, continuous processing on parade or rotary, by definition, allows only one average speed of movement inside the oven tunnel, only one temperature and only one type of mixture gas. A production of parts, for example sprockets, requires several treatment ranges depending on the different steels and the different target properties.

By definition, parade ovens can only be used for one type of treatment. As soon as several different treatments (for example different cementation depths) are required, it is necessary to have as many furnaces at the parade.

Another known method of carrying out thermochemical treatments followed by quenching in a press consists in dissociating the steps. Initially, the parts arranged in loads undergo a thermochemical treatment in a so-called "load" oven, arranged horizontally. They are then cooled slowly (to avoid deformation) under protective gas. Compared to the parade oven, this solution has the advantage of greater flexibility and a gain in floor space.

In a second operation, the pieces are heated again in another installation (typically a parade oven or a carousel oven) which allows them to be removed one by one or in small batches.

It is easy to understand that this process is very heavy and very expensive because it requires two types of ovens, significant handling operations and above all it is very disadvantageous from the energy point of view since it requires heating the parts twice.

In addition, both of them have no working flexibility since the installations are completely dedicated to the press quenching process and are not capable of offering other quenching variants. However, it is known that a heat treatment workshop requires various thermochemical processes and various means of quenching (liquid quenching, quenching under protective gas, etc.)

The state of the art is particularly illustrated by the installations of the company AFC-Holcroft in the USA with the reference "pusher furnaces" or "roratry earth furnaces" by those of the company Ipsen in Germany with the same reference as well as by the EP documents -A 1089 045 and US 4 105 398

The object of the invention is to overcome the drawbacks and limits which have just been explained in connection with these two embodiments. In fact, according to the invention, a single charge oven is used to carry out the thermochemical treatments in an extremely flexible manner and to extract the parts from the oven. This particularly advantageous and simple arrangement makes it possible to considerably rationalize production by minimizing handling operations, optimizing energy consumption and retaining the great processing flexibility inherent in charge ovens. To this end, the invention relates, according to a first aspect, to a method of heat treatment of metallic parts arranged under load, in which successively the load of parts is brought into a vertical treatment oven capable of being opened down, it is closed. the oven by means of a closure cap capable of supporting the load, the desired heat treatment carried out by the oven is then provided, and once this treatment has been carried out, the cap is characterized, characterized in that it is created between the opening of the furnace and the ambient air a process gas interface in a vestibule, one or more parts of the load are brought horizontally opposite a lateral opening made in the wall of the vestibule, this or these parts are entered from the outside through the said opening, this or these pieces are removed from the load and taken out of the vestibule, so that the piece or pieces located in the vestibule are protected from alteration of surfing ace by the process gases therein. According to this process, once the piece or pieces removed from the load and out of the vestibule, they are treated by means of a dipping press. One or more pieces of the load are brought horizontally opposite a lateral opening made in the wall of the vestibule, ensuring relative movement between the plug supporting the load and the oven. The parts of the same level are removed from the load and removed from the vestibule successively by pivoting the plug supporting the load. The operation consisting in bringing a piece opposite the lateral opening of the vestibule is repeated, grasping this piece from the outside, removing this piece from the load and removing it from the vestibule, successively for each piece or each group of parts to be treated by means of the dipping press. According to one embodiment, in order to bring the load of parts into the oven, the plug is opened and it is spread below the oven, the load is brought to the plug, and a relative movement of the plug is provided relative to the oven corresponding to an elevation of the cap until it comes to close the load. According to another embodiment, to bring the load of pieces into the oven, the pieces are brought onto the load through the lateral opening of the vestibule and the operation is repeated by making a relative movement of the plug and the oven until let the cap close the load. According to the embodiments, a stationary oven or a mobile oven in horizontal and / or vertical movement. According to the embodiments, the charge is maintained in the oven during the heat treatment by resting it on the plug or on projecting means of the oven.

According to a second aspect, the invention relates to an installation for heat treatment of metallic parts arranged under load specially intended for the implementation of the process which has just been described. This installation comprises at least one vertical treatment oven able to be opened downwards, fixed or mobile in horizontal and vertical movements, an oven closure cap able to support the load, a vestibule extending under the oven and comprising a lateral opening, drive means having the function of allowing relative movement between the plug and the oven, means for extracting the parts treated in the oven through the side opening of the vestibule, and at least one quenching press with which the extraction means cooperate.

According to a third aspect, the invention relates to an installation for heat treatment of metal parts arranged under load, comprising at least one vertical treatment oven capable of being open downwards, fixed or movable in horizontal and vertical movements, a closure cap of the oven capable of supporting the load, a vestibule extending under the oven, open downwards, fixed in horizontal movement, comprising above its lower edge a lateral opening having the function of allowing the extraction of the pieces from the inside outside the vestibule, drive means making it possible to perform relative vertical movements between the plug and the oven, means for extracting the treated parts to remove them from the load and take them out of the vestibule, means for gas tightness between the oven and the vestibule to allow the oven's protective gas to fill the vestibule once the oven is open, means for injecting u protective gas when the oven is opened, resulting from the separation between the plug and the oven. This installation also comprises at least one quenching press with which the means for extracting parts from the vestibule cooperate.

According to other characteristics of this installation, the lateral opening of the vestibule includes a closing door. The installation also comprises a device for rotating the plug with respect to a vertical axis of symmetry. According to one embodiment, the oven or ovens are arranged in a so-called upper position, are provided with means for maintaining the load in the absence of a plug and can be moved horizontally on a track. In this case, the installation also comprises one or more stationary quenching stations or tanks, each comprising a self-contained elevator, and the oven or ovens can be moved horizontally to come above the quenching stations or tanks. The furnace (s) can be moved above at least one station arranged in a lower position and comprising a vestibule with an opening, a plug and means for lifting said plug. The seal between the oven (s) and the vestibule (s) is ensured by a relative vertical movement of the oven and the vestibule and a joint system.

The invention will be well understood, as well as its advantages, thanks to the description which follows with reference to the appended drawings, in which: - Figure 1 is a schematic view, partial, in section, of an installation according to the invention according to a first possible embodiment, by a first vertical median plane, the plug being open, in the lower extreme position and supporting a load;

- Figure 2 is a schematic view, partial, in section, of the installation of Figure 1, along the section line AA and a second vertical median plane orthogonal to the first, the cap being closed in the extreme lower position and not supporting no load, the oven being empty;

- Figure 3 is a schematic view, in elevation, on a larger scale, of a possible embodiment of load of parts intended to be treated by an installation according to the invention; - Figure 4a is a schematic view from above of an installation according to the invention according to a second possible embodiment;

- Figure 4b is a schematic, partial view, in section, of the installation of Figure 4a, according to a vertical section plane, the plug being spaced from the oven and the load maintained in the oven by projecting means;

- Figure 4c is a schematic view similar to Figure 4b, showing other constructive features;

- Figure 4d is a schematic view similar to Figure 4b and 4c showing an embodiment with autonomous elevator; - Figures 5a, 5b and 5c are three schematic views of the process of introducing charge of parts into the furnace;

- Figures 6a, 6b and 6c are three schematic views of the process of opening the oven to unload the parts;

- Figures 7a and 7b are two schematic views of the process of unloading a part from the load of parts;

- Figure 8 is a schematic view of the process of introducing a part into the press;

- Figure 9 is a schematic view of the plug rotation process;

- Figure 10 is a schematic view of the continuation of the process of unloading the parts from the oven.

The installation according to the invention is intended for the heat treatment of metal parts 6 arranged to form a load 5 (Figure 3).

In general, the load 5 has a circular base. It comprises a base support or plate 7 and a series of intermediate plates 34 superimposed and spaced. The parts to be treated 6, for example pinions, discs, rings, etc., are arranged on the intermediate plates 34. Each plate 34 can support several parts 6 of the same or different nature. The spacing between the plates 34 is provided for example by spacers 35 and can vary depending on the height of the parts.

The installation firstly comprises, according to a first embodiment and Figures 1 and 2, a furnace 1 generally arranged vertically, with a vertical axis, capable of being opened downwards for loading and unloading. At furnace 1 is associated with at least one quenching press, not shown.

The oven 1 has at its external lateral periphery a metal carcass 2 containing a material insulating against thermal radiation 3 and providing spaces intended to receive heating elements such as gas burners 4 or electric heating candles.

The internal central part of the furnace 1 forms a space for receiving the load 5 arranged and capable of receiving, evacuating and containing the parts 6 to be treated resting on the plate 7. This space is delimited laterally in a cylindrical manner and upwards by a metal enclosure 8, the thickness of which can vary from 3 to 20 mm depending on possible embodiments. The enclosure 8 isolates the load 5 from the atmosphere generated by the burners 4. The enclosure 8 extends from the upper end of the furnace 1 to its lower limit.

The carcass 2 and the enclosure 8 open downwards delimit the lower opening of the furnace 1 allowing the introduction and the exit of the load 5. The dimensions of this opening are therefore accordingly.

In another possible embodiment, the oven 1 does not include an enclosure such as the enclosure 8. In this case, the gas heating is carried out for example by means of radiant tubes or in a similar manner in order to avoid disturbing the furnace atmosphere with the flue gases.

The oven 1 is also equipped with a stirring turbine 9, driven by a motor 10 placed outside the oven 1. The turbine 9, placed in and towards the top of the internal central part of the oven 1 forming the space receiving the load 5, above it, ensures the mixing of the gases constituting the internal atmosphere of the furnace 1. The installation also includes a movable and removable plug 11.

The plug 11 has a base plate 12 intended and arranged to be able to support the load 5 vertically using appropriate supports 13.

The plug 11 also includes thermal insulation 14. In addition, the plug 11 is intended and arranged to be able to close the oven 1 at its base where it is open, as has been described.

If a gas tightness is required during treatment, the plate 12 of the plug 11 is provided with a seal 15 which, once the plug 11 is placed in the closed position of the furnace 1, seals with the enclosure 8 or with the carcass 2 if there is no enclosure such as 8.

The various treatment fluids required for the thermochemical process, for example endothermic gas, nitrogen, hydrogen, ammonia, etc. are injected into the space for receiving the load 5 for example as illustrated in FIG. 1 by means of at least one injector 16 located here near the turbine 9.

The temperature measurements and the measurements making it possible to control or regulate the atmosphere in the furnace (probes, infrared analyzer, etc.) are carried out by means of one or more passages 17 arranged in the furnace 1, in communication with the exterior of the fouh.

The distribution of treatment fluids (flow rates meters, valves) and the measurements made in the furnace are typically managed by controllers or programmable controllers.

In one possible embodiment, the furnace 1 is fixed in horizontal displacement and is arranged in height with respect to the ground on which it rests by means of a superstructure such as a frame 18. The plug 11 is mounted movable in translation in the vertical direction and actuated by drive means 19, 20, in order to be raised or lowered in the vertical axis of the furnace 1. In the embodiment of FIG. 1, these drive means in the embodiment shown two guide columns 19, vertical, and a support 20, horizontal, carried by the columns 19. The plug 11 is fixed on the support 20. The drive means further comprise a reduction motor assembly and a rack, or any other means such as ball screw, pushing chain, actuator etc., similar, having the function of raising or lowering the support 20 and therefore the plug 11.

In one possible embodiment, no pit is dug intended to place the drive means, so as to reduce the civil engineering costs associated with the installation of the installation.

The drive means 19, 20 are arranged and in particular sized to allow the plug 11 to be raised and lowered and the load 5 once it has been placed on the plug 11. The total weight typically varies from 50 kg to several tonnes depending on the size of the oven. In general, the movement of raising and lowering of the plug 11 is associated with a position control means using for example an encoder, in order to allow the plug to be positioned precisely throughout its travel.

The distance between the furnace 1 and the ground is adapted to the height H of the load 5 so that the load can be placed on the plug 11 once it has been lowered to its lower position. Preferably, we seek to minimize the overall height of the installation, by adjusting the distance from the floor to the oven 1 as best as possible.

The establishment and removal of the load 5 on the plug 11 is typically carried out in the low position of the plug 11, using a pallet truck or a loading robot according to the degree of automation desired. The plug 11 is also provided with a rotation device without the horizontal plane, along the axis of the furnace 1, over 360 ° C. This rotation device comprises for example a bearing 21, a circular rack or a large pinion 22 driven by a reduction motor 23 provided with a pinion 24. Other embodiments are also possible. As for the drive means 19, 20, an incremental or absolute encoder can be used to control the angular position of the plug 11. In one embodiment, the rotation of the plug 11 relative to the furnace 1 or relative to the support 20 can occur over the entire vertical stroke of the plug 11, the rotation device and its actuator being on board the plug 11. In another embodiment, the rotation of the plug may not be actuated at any point in its vertical stroke.

At its base, the oven 1 is equipped with a vestibule 25 integral with the enclosure 8 or with the carcass 2 if there is no enclosure.

Vestibule 25 is open downwards.

The vestibule 25 is connected to the enclosure 8 or to the carcass 2, respectively, by means for example of a gas-tight seal system 26.

The vestibule 25 can be considered as an extension of the furnace 1, respectively of its enclosure 8 or of its carcass 2, downwards.

The vestibule 25 extends vertically under the oven 1 over a height typically between 100 mm and the distance separating the bottom of the oven from the floor. For example, we can consider for the vestibule a height of about 300 mm.

The vestibule 25 can be formed for example by a sort of ferrule made of rolled or folded sheet steel, thermally insulated or not, heated or not.

The vestibule 25 is arranged to allow the passage of the support plate 7 and the plug 11 when the plug 11 is raised or lowered.

The lower part of the vestibule 25 is arranged to prevent gas from remaining trapped in the vestibule 25. For example, it is devoid of sealing means. The vestibule 25 also includes one or at least one lateral opening 27 whose function is to allow one or more pieces 6 to be taken from the load 5 in order to bring them onto the quenching press or presses. Given its function, the opening 27 is of sufficient size to allow the passage of the parts 6.

The opening 27 is made in the upper part of the vestibule, closest to the oven 1.

In one possible embodiment, the opening 27 is furnished with a door 28 or with a curtain mounted movable by pivoting or sliding by means, for example, of a pneumatic cylinder 29 carried by the wall of the vestibule 25 in order to be able to open or close the opening 27. This door 28 can for example roll over part of the wall of the vestibule while being guided by a device of rails and rollers 30.

When the plug 11 of the furnace 1 is opened, the supply of treatment gas to the furnace 1 through the injector (s) 16 is maintained, which avoids air damaging the quality of the parts 6 does not enter the oven 1 by creating an overpressure.

If flammable treatment gases are used, an igniter 31 placed in the immediate vicinity of the bottom of the oven 1, or even of the lower end of the vestibule 25, is used to allow a curtain of flames to be created which prevents possible air intrusion in the oven 1.

The sealed connection 26 between the vestibule 25 and the enclosure 8 (or the carcass 3) makes it possible, when the plug 11 is opened, to shift the interface between the atmosphere of the furnace 1 and the ambient air by the axial height of the vestibule 25. Thus, each time the plug 11 is opened, the volume delimited by the vestibule 25 is filled with gases from the oven 1.

According to one embodiment (see FIG. 2), there is a seal 32 disposed on the door 28 or on the wall of the vestibule 25 to ensure gas tightness when the door 28 is closed under the action of its drive cylinder. According to one embodiment, a manual device for opening the door 28 is provided.

In certain cases, in particular for ovens with large diameters (more than 1000 mm in diameter), it is possible to provide a supply of protective gas directly into the vestibule 25 by means for example of an additional injector 33 shown here in the form of '' a ring with holes or injection nozzles.

The construction of the vestibule 25 makes it possible to bring the pieces 6 into the vestibule 25 by lowering the plug 11 or by raising the oven 1. The oven 1 is, depending on the embodiments, fixed or mobile in horizontal and / or vertical movements. In all cases, the installation is such that the vestibule 25 allows relative movement with the plug 11 of the oven.

The operation of the installation according to the invention will now be described.

Firstly, the oven 1 is empty and closed at the bottom by the plug 11.

The plug 11 is lowered by the drive means 19, 20 used for this purpose to bring it into its lower position.

The plug 11 being in its lower position, the load 5 is placed on it (FIG. 5a) previously constituted with the parts to be treated 6 using the means provided for this purpose (pallet truck, robot, etc.).

The plug 11 is then raised and therefore the load 5 (FIG. 5b) which it supports thanks to the drive means 19, 20 used for this purpose to bring the plug into its upper position in which it closes the oven 1 ( Figure 5c). In addition, the load 5 is thus brought into the internal central part of the oven 1 forming a receiving space. In this situation, the door 28 of the opening 27 is closed. The gas burners 4 or other similar elements intended to bring the load 5 to the temperature required by the thermochemical treatment are then used. If a thermochemical treatment is required, it takes place once the pieces 6 of the charge have reached the treatment temperature. These thermochemical treatments are generally of long duration, typically from 3 to 48 hours.

At the end of the thermochemical treatment, the atmosphere of the oven 1 is conditioned in order to pass to the quenching step. In this case, the treatment gases are limited to a protective role to prevent the composition of the surface of the parts 6 from being modified. Typically, either a neutral atmosphere such as nitrogen, mixtures of methane hydrogen nitrogen, ammonia, or controlled atmospheres such as endothermic gas are used, the oxidizing or fuel power of which is regulated by additions of propane or air. Once the thermochemical and quenching treatment is complete, the plug 11 is opened by lowering it (FIG. 6a). The treatment gases then fill the vestibule 25 to form an interface with the air located at the lower end of the vestibule 25.

The plug 11 and the load 5 are lowered (FIG. 6b) thanks to the drive means 19, 20 implemented for this purpose so as to bring the parts 6 disposed on the first intermediate plate 34 'horizontally opposite the opening lateral 27 formed in the vestibule 25. By first intermediate plate 34 ′, it is understood the plate closest to the plug 11 and supporting parts 6. The parts 6 located in the vestibule 25 are protected from surface alteration by the process gases therein. The rooms 6 of the upper levels are also protected by the atmosphere of the oven and are located for the most part in a heated area, which means that they are kept at working temperature. The door 28 of the opening 27 is then opened by means of the jack 29 (FIG. 6c) or by other similar means. In this situation, and as a result of the lowering of the plug 11 and of the load 5, there is a part 6 located directly opposite the opening 27 then open. In this situation, one is able to grasp this part by means of pliers or by means of a robot, from outside the vestibule 25 and through the opening 27 (FIG. 7a). We can then remove this part 6 of the load 5 and take it out of the vestibule 25 by means of pliers or the robot and bring it under the soaking press. This operation only takes a few seconds (Figures 7b and 8)

The part 6 in question is then treated, by means of the dipping press.

The door 28 is closed to avoid contamination of the atmosphere of the vestibule 25.

In general, an installation of this type comprises several ovens and several dipping presses. Depending on the availability of the dipping presses and / or the mass or the number of parts 6 placed on the plate 34 ', two operating modes can be provided.

For massive pieces 6, which cool very little when they are positioned in the unheated vestibule 25, it can be considered that all the pieces 6 located on the same tray 34 will be removed without the cap 11 being closed, it that is to say without the parts 6 of said plate 34 being then replaced in the oven 1 by raising the plug 11. Once the first part 6 has been removed, the device 21, 22, 23, 24 for rotating the plug 11 is put in place. work (Figure 9) so as to operate an angular rotation of the plug 11 adapted to allow to present another part 6 opposite the opening 27. This other part can then be removed. The process is thus repeated until all the parts 6 of the first plate 34 'are removed from the installation.

If the availability of the dipping presses is insufficient to quickly absorb the parts to be treated, or if they risk cooling too quickly, the plug 11 is raised to replace the parts of the tray 34 'in the oven 1, respectively in the zone heated. Once the parts have warmed up, the operation described above takes place again. The rotation of the plug 11 in order to present the parts 6 facing the opening 27 can be carried out at any height situated between the upper position of the plug 11 and that corresponding to the placing of the parts 6 of the tray in question and of the opening 27 .

All the operations which have just been exposed can be commanded and controlled using process management software, by associating with each part 6 a maximum duration of maintenance in the vestibule 25.

Once all the parts 6 have been removed from a plate 34, and depending on the availability of the dipping press, the plug 11 is closed.

The operation continues in the same sequence (Figure 10) until all the parts 6 of all the trays 34 are removed from the load 5 and the oven l.

The invention is not limited to the embodiment which has just been described. Thus, it can be envisaged that all of the plates 34 and of the support 7 remain integral with the plug 11 in production. The loading of the parts to be treated 6 is then done one by one according to a process which is the reverse of that described above for unloading. In this case, the loading is carried out through the opening 27, or through another similar opening provided for this purpose and arranged elsewhere on the wall of the vestibule.

Likewise, the relative elevation movement between the furnace and the plug can be reversed, the furnace 1 provided with its vestibule 25 being provided with drive means similar to the means 19, 20 described and moved in translation upwards and towards the bottom. In this embodiment, the plug 11 remains in the same vertical position. He can keep his rotation device 21, 22, 23, 24. We now describe a second possible embodiment of the installation with reference to Figures 4a, 4b, 4c and 4d.

In this second embodiment, the furnace 1 is also disposed in the upper position, but it is movable horizontally in lateral translation by means for example of wheels 35 mounted rolling on a track which, in one embodiment is in the form of guide means such as rails 36. The displacement means 35, 36 allow the oven 1 to be placed above different stations 37 located in the lower part. The furnace 1 can be driven by a motor and rack assembly or by any other similar means.

A locking device is disposed in the oven 1. This device comprises, in the embodiment under consideration, projecting means 38. The projecting means 38 are arranged and able to receive the support 7 of the load 5 and thus to support the latter. They thus allow the load 5 to be locked. The load 5 is anchored in the oven 1 can be carried out by lateral or rotary relative movements of the oven 1 and the plug 11 or by rotation of the projecting means 38.

The locking device keeps the load 5 in the oven 1 when the plug 39 is removed, which closes the oven 1 at its base. The plug 39 is generally similar to the plug 11 previously described. As previously in the corresponding embodiment, the plug 39 is provided with drive means for lifting or lowering it 40.

As indicated, the installation may also include one or more stations 37 which extend under the horizontal axis of movement of the oven (s) 1, in addition to the ovens 1 which can move horizontally. These stations 37 can for example be quenching tanks containing liquid or gaseous fluids (FIG. 4d). These stations 37 are conventionally provided with an autonomous elevator 41 whose stroke is adapted to allow the load 5 to be transferred from its position in the oven 1 to its position in one of the lower stations 37. As this As a result of FIG. 4a, the furnace (s) 1 are movable above the lower stations 37 to allow the loads 5 to be transferred to one or the other of said lower stations.

Reference is now made to FIG. 4c which illustrates an installation embodiment which also comprises at least one specific station 42 intended for quenching in press. This station 42 includes a rotary plug assembly 43 provided with its drive means 44, which are similar to those 19, 20, already described in relation to the first embodiment of FIG. 1. The press quenching station 42 also includes a vestibule 45 analogous to vestibule 25 of the first embodiment of FIG. 1, provided with a lateral opening 46 and with a door 47 but open both upwards and downwards.

At its upper end, the vestibule 45 has a gas seal system 48 which makes it possible to seal between the oven 1 and the vestibule 44 once the oven 1 has been placed above the station press quenching 42. This arrangement allows the load 5 to be transferred to the cap 43 of the press quenching station 42. Several embodiments within the reach of those skilled in the art can be envisaged to ensure sealing by arranging a small spacing of the order of a few millimeters for example between the lower plane of the oven and the seal system 48 to allow the displacement of the oven 1: inflatable seal, brush-type static seal, relative vertical movement of the oven and the vestibule, etc. . Once oven 1 and the vestibule 45 are placed in superposition and tightly coupled by means of the seal system 48, there is an arrangement similar to that already described in relation to the first embodiment of FIG. 1.

The quenching operations in the press, or more precisely the removal of parts from the oven, are carried out in a manner analogous to what has already been described. The invention allows a rationalization of production and flexibility unmatched until now. Indeed, an installation can typically comprise several static or mobile ovens, several quenching stations with fluids or in press.

In contrast to known techniques, the invention, by its modular nature, makes it possible to adapt production variations or productivity at any time by adding modules or by increasing the number of available processes (multiple quenching possibilities, multiple thermochemical processes , etc.).

Claims

1. A method of heat treatment of metal parts (6) arranged as a load (5) in which successively the load (5) of parts (6) is brought into a vertical treatment oven (1) capable of being opened downwards, the oven (1) is closed by means of a closure plug (11) capable of supporting the load (5), the desired heat treatment carried out by the oven (1) is then provided, and once this treatment has been carried out, opens the plug (11) characterized in that a process gas interface is created between the opening of the oven and the ambient air in a vestibule (25), one or more pieces (6) of the charge are brought (5) horizontally opposite a lateral opening (27) formed in the wall of the vestibule (25), this or these pieces (6) are grasped from the outside through said opening, this or these pieces are removed ( 6) of the load (5) and it is taken out of the vestibule (25), so that the part or parts (6) located in the vestibule (25) are protected affected by surface alteration by the process gases therein.

2. Method according to claim 1, characterized in that once the part or parts (6) removed from the load (5) and out of the vestibule (25), they are treated by means of a press (42) to soak.

3. Method according to any one of claims 1 and 2, characterized in that one or parts (6) of the load (5) is brought horizontally opposite a lateral opening (27) formed in the wall of the vestibule (25) ensuring relative movement between the plug (11) supporting the load (5) and the oven (1).

4. Method according to any one of claims 1 to 3, characterized in that the parts (6) are removed from the same level of the load (5) and they are removed from the vestibule (25) successively by pivoting the plug (11) supporting the load (5).

5. Method according to any one of claims 1 to 4, characterized in that the operation consisting in bringing a part (6) opposite the lateral opening (27) of the vestibule (25) is repeated, grasp this part (6) from the outside, remove this part from the load (5) and take it out of the vestibule (25), successively for each part (6) or each group of parts to be treated by means of the press (42) to soak.

6. Method according to any one of claims 1 to 5, characterized in that to bring the load (5) of parts (6) in the oven (1), the plug is opened (11) and it is spread below from the oven (1), the load (5) is brought to the plug (11), and a relative movement of the plug (11) is provided relative to the oven (1) corresponding to an elevation of the plug until he comes to close the load (5).

7. Method according to any one of claims 1 to 5, characterized in that to bring the load (5) of parts (6) in the oven (1), the parts (6) are brought on the load (5) to through the lateral opening (27) of the vestibule (25) and the operation is repeated by carrying out a relative movement of the plug (11) and the oven (1) until the plug (11) comes to close the load ( 5).

8. Method according to any one of claims 1 to 7, characterized in that one implements a stationary oven or a mobile oven in horizontal and / or vertical movement.

9. Method according to any one of claims 1 to 8, characterized in that the charge is kept (5) in the oven (1) during the heat treatment by resting it on the plug (11) or on means projections (38) of the oven (1).

10. Installation for heat treatment of metal parts (6) arranged in charge (5) specially intended for the implementation of the method according to any one of claims 1 to 9, this installation comprising at least one treatment oven (1) vertical able to be opened downwards, fixed or movable in horizontal and vertical movements, a plug (11) for closing the oven (1) capable of supporting the load (5), a vestibule (25) extending under the oven (1) and comprising a lateral opening (27), drive means (19, 20) having the function of allowing relative movement between the plug (11) and the oven (1), means for extracting the parts (6) treated in the oven (1) through the lateral opening (27) of the vestibule (25), and at least one quenching press (42) with which the extraction means cooperate.

11. Installation for heat treatment of metal parts (6) arranged as a load (5) comprising at least one furnace (1) for vertical treatment capable of being open downwards, fixed or movable in horizontal and vertical movements, a plug (11 ) closing the oven (1) capable of supporting the load (5), a vestibule (25) extending under the oven (1), open downwards, fixed in horizontal movement, comprising above its lower edge a lateral opening (27) having the function of allowing the extraction of the parts (6) from the inside to the outside of the vestibule (25), drive means (19, 20) making it possible to perform relative vertical movements between the plug (11) and the oven (1), means for extracting the treated parts (6) to remove them from the load (5) and take them out of the vestibule (25), sealing means (26) between the oven (1) and the vestibule (25) to allow the oven's protective gas (1) to fill the vestibule (25) once the oven (1) is open, means (16) for injecting protective gas when the oven (1) is opened, resulting from the separation of the plug (11) and the oven (1 ).

12. Installation according to claim 11, characterized in that it further comprises at least one quenching press (42) with which the means for extracting the parts (6) from the vestibule (25) cooperate.

13. Installation according to any one of claims 11 and 12, characterized in that the lateral opening (27) of the vestibule (25) comprises a closing door (28).

14. Installation according to any one of claims 11 to 13, characterized in that it further comprises a rotation device (21, 22, 23, 24) of the plug (11) relative to a vertical axis of symmetry.

15. Installation according to any one of claims 11 to 14, characterized in that the oven (s) (1) are arranged in a so-called upper position, are provided with means for maintaining the load (38) in the absence of plug (11) and can be moved horizontally on a track.

16. Installation according to claim 15, characterized in that it further comprises one or more stations or quenching tanks (42) fixed each comprising an autonomous elevator, and in that the oven (s) (1) are horizontally displaceable for come above the quenching stations or tanks (42).

17. Installation according to claim 15, characterized in that the furnace (s) (1) can be moved above at least one station arranged in a lower position and comprising a vestibule (25) with an opening (27), a plug (11) and lifting means (19, 20) of said plug.

18. Installation according to claim 17 characterized in that the seal between the oven (s) (1) and the vestibule (s) (25) is ensured by a relative vertical movement of the furnace (1) and the vestibule (25) and of a joint system (26).