EP1065287A1 - Heat treatment installation with at least a muffle furnace - Google Patents

Abstract

The furnace (1) is designed to open laterally to allow the pot (5) carried by the handling unit, to enter into the oven and to leave it by lateral displacement.

Description

The present invention relates to a heat treatment installation for parts grouped in the form of a load in pots, the installation comprising stations and a handling device to transport the pots from a station to a other, at least one of the stations comprising an oven arranged to receive and laterally surround one of the pots to subject it to a processing step thermal.

The technology of so-called "pot ovens" has been known for many years in the field of heat treatment of formed metal parts in loads or in batches (arranged pieces, arrangements of baskets of loose pieces or not).

In general, pot ovens are intended for loads of large volume (typically greater than 0.5 m ³ ), contained in generally cylindrical pots whose vertical dimension (height or depth) is much greater than the diameter. Heights of several meters are common.

• d'une part on distingue les traitements au cours desquels la charge des pièces est retirée du four et du pot à haute température par un mouvement vertical, une fois que le couvercle du pot est ouvert, et déplacée au dessus d'une cellule dite de trempe dans laquelle elle est ensuite immergée (les bains de trempe peuvent être de l'eau, des solutions de polymères, de l'huile, des mélanges de sels fondu ou du gaz);
• d'autre part on distingue les procédés pour lesquels les pièces et la charge restent en permanence à l'intérieur du pot fermé et pour lesquels le pot fermé et la charge de pièces sont retirés du four par un mouvement d'élévation vertical du pot à une température donnée pour être déplacés au dessus d'une autre station dans laquelle ils sont introduits par un mouvement d'abaissement vertical. Ces opérations de manutention sont nécessaires pour passer par exemple d'un four à un autre four, ou d'un four à une station de refroidissement (afin notamment de ne pas avoir à refroidir le four, ou pour des raisons liées au traitement métallurgique). Les procédés utilisant cette technologie sont par exemple le revenu, le recuit, l'austénitisation, la nitruration, la nitrocarburation, le préfrittage, etc.

Installations of pot or well ovens include one or more heat treatment furnaces in which pots of refractory material are housed, containing the charge of the parts to be treated and closed by a cover with or without a setting device. circulation of treatment gases which are introduced into the pot during the course of the heat treatment at temperature. There are two types of heat treatment processes associated with this type of installation:

• on the one hand we distinguish the treatments during which the load of the parts is removed from the oven and the pot at high temperature by a vertical movement, once the lid of the pot is open, and moved above a cell called quenching in which it is then immersed (the quenching baths can be water, solutions of polymers, oil, mixtures of molten salts or gas);
• on the other hand, a distinction is made between the processes for which the parts and the load remain permanently inside the closed pot and for which the closed pot and the load of parts are removed from the oven by a vertical elevation movement of the pot to a given temperature to be moved above another station into which they are introduced by a vertical lowering movement. These handling operations are necessary to pass for example from an oven to another oven, or from an oven to a cooling station (in particular so as not to have to cool the oven, or for reasons related to metallurgical treatment) . The processes using this technology are for example tempering, annealing, austenitization, nitriding, nitrocarburizing, pre-sintering, etc.

In both cases, the movements of raising and lowering are carried out for example by means of a hoist suspended from the building.

The present invention applies essentially to installations of the second category, for which the charge remains inside the pot.

Known installations of this kind have several disadvantages.

First, they require a very high building height important to allow the pots to be inserted into ovens open upwards, extract them and transfer them to other stations. In most of case, the size of the workshops does not allow easy integration of furnace installations with pots. The civil works necessary to place the ovens in pits are very expensive and are not achievable in most cases.

Second, the transfer of the pot from the oven to a cooling station taking place at a high temperature (typically between 500 ° C and 1100 ° C), it a strong release of heat and a strong thermal radiation occurs during transfer of the pot, which are harmful to the ergonomics and safety of users.

Third, the different gases and other supplies (water from cooling, electricity, etc.) are manually disconnected from the pot due to the amplitude of the movements of elevation of translation and lowering, to be reconnected manually once the pot is housed in another station. This disconnection of the pot from its control and safety devices is considered to be delicate and dangerous, especially since the hot pot can contain significant amounts hydrogen.

In some cases it is possible to provide supply lines flexible enough to accommodate movement, but this measure is very expensive and the pipes must be shielded to resist radiation from the hot pot being treated. Finally, we understand that it is thus practically impossible to perform transfer operations automatically, this which induces a very significant labor cost for the use of the installations of pot ovens.

The subject of the invention is an installation comprising one or more ovens with pots and to overcome all of these disadvantages.

To this end, the invention relates to an installation of the type indicated in preamble, characterized in that the oven is arranged to open laterally for allow the jar transported by the handling device to enter the oven and to get out of it by lateral displacement.

Thanks to this arrangement, each pot can enter and leave the oven without have to be raised to its full height. As the pot usually rests on the top of the oven, just lift it a few inches to then be able to move it horizontally for transfer between the oven and the other stations. If the pot is suspended from a cart running on a track, the cart may be a low height above the oven and other devices forming the stations the installation, i.e. the height of the entire building housing installation can be significantly reduced. In addition, the size of the screens protecting the around the stations against the thermal radiation of the pots can also be scaled down. Finally, as the vertical amplitudes of the pot movements are very reduced, it is much easier to keep any possible pipeline connections between central power supplies and pots during movement.

la figure 1 est une vue en coupe horizontale schématique d'une première forme de réalisation d'une installation selon l'invention, comportant un four à pot;

la figure 2 est une vue en coupe verticale schématique du four de l'installation selon la figure 1;

la figure 3 est une vue en plan schématique partiellement coupée d'une seconde forme de réalisation d'une installation selon l'invention, comportant deux fours à pots et un chariot de transfert; et

la figure 4 est une vue en coupe verticale schématique d'un four de l'installation selon la figure 3.

Other characteristics and advantages of the invention will emerge from the following description of two embodiments, presented by way of nonlimiting examples with reference to the appended drawings, in which:

Figure 1 is a schematic horizontal sectional view of a first embodiment of an installation according to the invention, comprising a pot furnace;

Figure 2 is a schematic vertical sectional view of the installation furnace according to Figure 1;

Figure 3 is a partially cut schematic plan view of a second embodiment of an installation according to the invention, comprising two pot ovens and a transfer carriage; and

FIG. 4 is a schematic vertical section view of an oven of the installation according to FIG. 3.

In the first embodiment shown in FIGS. 1 and 2,
the installation comprises a pot furnace 1 open upwards, comprising for example an external carcass 2, a layer of thermal insulation 3 and heating elements 4 here represented by electric heating bodies. Other heating means such as gas or oil burners are obviously possible. This oven is designed to receive a substantially cylindrical treatment pot 5, of diameter D and of length H, provided with a removable cover 6 which can be made integral with the pot by means of fasteners not shown and possibly provided with means for mixing the confined atmosphere in the pot, as will be described in the second example, as well as various connections 7 for supplying the pot with treatment gas and electricity.

The installation further includes a cooling cell or station 8 and a handling device for raising, lowering and moving the pots, shown here by a hoist 11 rolling on a track 29 fixed under an upper structure 13 of the building, the hoist being provided with a winch 14. The cooling cell 8 is mainly consisting of a chassis and a thermally insulated carcass 9 or no, which supports the treatment pot 5 once engaged in the cell. Cell 8 can be fitted with a fan 12 which brings cold air into contact with the pot when it is housed in the cell. Cooling cells like this can also be equipped with numerous devices to increase the speed of cooling of the treatment pot 5, such as for example injection devices sprayed liquids, nozzles arranged around the pot, etc.

It is understood that the installation may include several furnaces treatment or tempering 1, several pots 5 and several cooling cells 8.

The oven 1 is designed to open in two parts 10 and 10 'so that the spacing of the two parts of the oven, equal to or greater than the outside diameter D of the treatment pot 5, allows the treatment pot 5 to be moved laterally from the center from oven 1 to a position outside the open or closed oven, without it being necessary to completely remove the pot 5 from the oven 1 by a vertical movement on its entire height H before any lateral translational movement of the pot.

The means allowing the complete or partial opening of the oven are not indicated but can typically include a combination of cylinders, chains pushers or racks, etc. and relative sliding plans between the fixed and mobile parts. In Figure 1, the moving parts of the oven are shown by two half-shells 10 and 10 'obtained by cutting the oven according to a passing plane by the vertical axis of the oven. Other embodiments are possible, for example in the case of ovens (round base, square rectangular, polygonal, etc.) for which the two moving parts 10 and 10 ′ have a height less than the full height of the oven 1, but preferably extend over most of the height H and at less to the top of the oven. In such a case, the pot should be raised in a limited measure before moving it sideways.

In the example shown, the two movable parts 10 and 10 'deviate one on the other so as to provide a larger free space than D, which allows the translational movement of the pot in two opposite directions. We can obviously consider another arrangement where the two moving parts 10 and 10 ' move away from each other by pivoting on a hinge located on a generator of the outer casing 2 of the oven.

The cooling cell 8 is designed on the same principle as the oven 1 and has two movable parts 15 and 15 'whose height agrees with that of parts 10 and 10 'of the oven.

In the example described here, we consider a situation where the track 29 of the hoist 11 extends above the furnace 1 and the cooling cell 8 and is located at a low height from the top of the oven. This allows the support structure 13 to be, above the oven 1 and the pot 5, at a limited height H 'which represents the vertical dimensions of the handling device. This height H 'is much less than the height of the pot H, so that the vertical movement of the pot 5 ensured by the winch 14 is only a few centimeters, for example 10 cm so that the pot has a height H of more than 200 cm.

First, the load to be treated is placed in the pot 5 and the pot is closed by means of cover 6. The various fluid lines and supplies necessary for the course of treatment are connected to pot 5 at by means of the connections 7 located for example on the cover 6. The length and the nature of the pipes and supplies between connections 7 and the cabinets distribution (not shown) are studied so that the pot 5 is connected in permanence at the central distribution regardless of its position in the installation.

The assembly consisting of the pot 5 and its cover 6 is attached to the hoist 11 and raised a few centimeters to provide a small distance between its edge upper 16 and the top of the oven 1. The oven 1, which may already be at a temperature high (between 500 ° C and 1000 ° C), is opened by the relative movement of its parts mobile 10 and 10 '. The pot 5 provided with its cover 6 is introduced into the center of the oven in the by means of a lateral translation effected by the hoist 11. The oven 1 is then closed and the pot 5 is lowered into the oven so that its rim 16 rests on the upper part of the oven 1. At this stage, the hoist 11 can be separated from the pot if necessary. The heat treatment cycle in the oven can then begin.

At the end of the heat treatment cycle in the oven, the hoist 11 is returned integral with the assembly consisting of the pot 5 and its cover 6, the pot is raised by i a few centimeters above the top of oven 1, oven 1 is open as in the case of the loading described above, the cooling cell 8 is also open by moving the moving parts 15 and 15 'to allow the hoist 11 to bring the pot 5 to the center of the cell 8 by horizontal translation, the cell 8 is closed, the winch 14 deposits the pot 5 provided with its cover 6 on the upper part of cell 8 and the cooling cycle can be carried out.

The relative vertical movement between the constituted surfaces respectively by the upper part of the oven 1 and by the upper rim 16 of the pot is not absolutely necessary. In the case described, this movement is ensured by the winch 14 but it’s perfectly imaginable, in case this movement is necessary, whether it is carried out by a vertical movement of the furnace or the cooling or by a fixed or mobile device arranged on the furnace or the cooling cell.

It will also be noted that it would be sufficient for only one of the parts 10 and 10 'of the furnace 1 and / or only one of the parts 15 and 15 ′ of the cooling cell 8 is movable at the way of a door to allow to move the pot 5 laterally.

Instead of rolling on track 29, the hoist 11 could for example be suspended to a pivoting bracket whose axis would be between the oven 1 and the cell 8. On the other hand, instead of the hoist 11, we can consider handling the pot 5 with a device supporting the pot from below, for example a transport cart whose surface upper has thermal insulation, this carriage circulating below the treatment stations.

In Figures 3 and 4 are shown a treatment oven 1 opening in two parts 10 and 10 'as in the previous example, two cells of cooling 17 and 18 also opening in two parts similarly to the oven 1, and a tempering oven 19 also opening in two parts 20 and 20 '. The installation also includes a station 21 which makes it possible to enter the pot or pots 5 in the installation and extract them. In this example, the cover 6 of each pot is equipped with an atmosphere stirring device, comprising a motor 30 mounted on the cover 6, a shaft and a stirring wheel 31 disposed under the lid inside the pot 5.

A cart 22 for handling and transporting the pots is arranged above of the plane defined by the upper surface of the ovens and other stations the installation. The carriage 22 is equipped with a device 23 for gripping the assemblies each consisting of a pot 5 and its lid 6. The gripping device 23 can by example be made by pliers or by a cam mechanism or by a bayonet system. The gripping device 23 couples to the cover 6 to lift and transport the entire pot and lid. Also it can handle the lid only when it is detached from the pot. The carriage 22 is movable along the installation to allow the pots to be moved by translation in all of the elements or stations making up the installation.

In the example shown, the carriage 22 is movable on a track 24 consisting for example of two rails, by means of wheels 25 and a means of translation not shown. Track 24 can be supported for example by a structure of the building or by porticoes. As a means of translation, we can by example imagine an electric motor driving a pinion on a rack, a jack or a device using a push chain. The example of Figures 3 and 4 is not unique and one can perfectly imagine a track arranged on the side of the elements or on the ground and consisting of one or more rails or any other guiding and moving means. There can also be multiple carts and several tracks supporting wheels or for example slides with marbles.

The closed jar (s) are permanently connected to the power supplies power plants (process gas, power supply, water supply from cooling, etc.) by means, for example, of flexible pipes 26 arranged in a cable chain 27.

This installation makes it possible to move the pot (s) 5 automatically in the various stations to carry out treatment sequences such as for example austenitization in oven 1, quenching in the cell cooling 18, a first tempering in the tempering furnace 19 followed by a cooling in the cooling cell 18, a second tempering in the furnace income 19 and so on. All movement movements of the pot (s) 5 are carried out by the handling device consisting of the carriage 22, the device 23 and the track 24. The handling operation sequences can be controlled by a conventional programmable controller.

The installation can also be equipped with an external fairing 25 which confines the radiation of transfer pots.

By design, the installation described is not limited to a configuration where the different elements or stations of the installation are arranged on a line or a map. Arrangements on several lines, parallel or not, are perfectly achievable, either by a transfer member (carriage) on several axes, or by allowing the various elements of the installation to pivot.

• une diminution très importante des hauteurs de bâtiments nécessaires à la mécanisation de la manutention des pots, en rendant possible un transfert horizontal des pots sans nécessiter de mouvements verticaux des pots;
• une parfaite maítrise de la sécurité lors du transfert des pots (les pots restent connectés en permanence aux alimentations centrales), permettant de mettre en oeuvre les opérations d'urgence en cas de problème;
• un confinement des rayonnements et des dégagements de chaleur lors du transfert des pots en évitant de devoir extraire les pots au-dessus des fours;
• une automation des enchaínements de transfert des pots.

The invention described therefore overcomes the main problems associated with pot furnace installations, namely:

• a very significant reduction in the heights of buildings necessary for the mechanization of the handling of the pots, making it possible to transfer the pots horizontally without requiring vertical movements of the pots;
• perfect control of security during the transfer of the pots (the pots remain permanently connected to the central power supplies), allowing emergency operations to be implemented in the event of a problem;
• containment of radiation and heat generation during the transfer of the pots, avoiding having to extract the pots above the ovens;
• automation of the pot transfer sequences.

Thanks to the invention, these essential advantages are obtained by means of simple and inexpensive solutions that give an extremely profitable character to the invention.

Claims (10)

Installation for heat treatment of parts grouped in the form of a load in pots (5), the installation comprising stations and a handling device (11, 22-24) for transporting the pots from one station to another, at least one of the stations comprising an oven (1) arranged to receive and laterally surround one of the pots to subject it to a heat treatment step,
characterized in that the oven (1) is arranged to open laterally to allow the pot (5) transported by the handling device to enter and exit the oven by lateral movement. Installation according to claim 1, characterized in that the furnace opens laterally to a height substantially equal to the height (H) of the pot (5). Installation according to claim 1, characterized in that the furnace opens laterally to a height corresponding to most of the height (H) from the pot. Installation according to claim 1, characterized in that the furnace (1) is open upwards, in that an upper part of each pot (5) has means (16) for resting on an upper part of the oven and in that the device handling (11, 22-24) extends above the oven and other stations installation, the pot being suspended from this device for transport. Installation according to claim 4, characterized in that the device handling has a height (H ') above the oven (1) which is smaller as the height (H) of said pot (5). Installation according to claim 4, characterized in that the device handling comprises means (14) for raising and lowering the pot (5) in each station. Installation according to one of claims 4 to 6, characterized in that each pot has an upper lid (6) removably attached to the pot and in that the handling device comprises gripping means (23) arranged to hang on to said lid and thus support the entire pot and lid. Installation according to one of the preceding claims, characterized in that the oven (1) has two movable parts (10, 10 ') joined along planes vertical and arranged to move laterally apart from one another to open the oven. Installation according to one of the preceding claims, characterized in that said stations also include at least one preparation station, conditioning, heat treatment or cooling (17, 18, 19), which comprises an enclosure arranged to laterally surround one of the pots (5) and for open laterally similar to the oven (1) for the entry and exit of the pot. Installation according to one of the preceding claims, characterized in that each pot (5) has connections (7) for its supply of fluids or in energy and in that the installation comprises flexible pipes supply (26) arranged to remain connected to said connections (7) for transport of pots.

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