EP0150652A1 - Process and device for elaborating and casting an alloy under vacuum - Google Patents

Abstract

The invention relates to centrifugal casting. The furnace (1) processes the metal in a vessel (3) under vacuum. The liquid metal is poured into the spout (10) and then centrifuged at (7) in the vessel (6) under vacuum. The valve (5) can separate the two vessels (3) and (6). Application: processing of special alloys for centrifugal casting. <IMAGE>

Description

The present invention relates to a method and a device for the preparation under vacuum of a metallic alloy and for its shaping by centrifugation.

The purpose of vacuum metallurgy is to allow the development of alloys, certain constituents of which combine at the temperature of the liquid metal with one or the other of the constituents of air (oxygen, nitrogen, hydrogen, etc.). .) or to allow a better elaboration of alloys which can be elaborated in air, but whose mechanical, physical characteristics etc. are improved by an elaboration in the absence of atmosphere.

The melting and vacuum production of metal alloys is a known technique.

In a conventional arrangement, a melting furnace, generally with electric induction, is placed in a sealed enclosure comprising an access device provided with an equally sealed closure. '' A charge, composed of the alloy, is introduced into this oven to melt or metallic elements or master alloys allowing the constitution of the alloy and, after having closed the enclosure and having extracted the gaseous mass which it contains using the appropriate pumps until a vacuum is obtained more or less pushed, to apply the energy necessary for the fusion of one alloy.

Once the alloy has melted, and its composition verified, it is generally transferred from the oven to a mold or an ingot mold, located in the same enclosure.

After the metal has solidified, the air is allowed to enter the enclosure until the atmospheric pressure is restored. We can then take the ingot or the part thus molded.

Among the methods of forming alloys by fusion, then solidification, centrifugation or centrifugal casting, is known as being a process which makes it possible to obtain tubular or annular hollow bodies, or even shaped parts, particularly healthy and having good physical and mechanical characteristics.

It consists in introducing a liquid metal into a generally cylindrical mold, generally turning around its geometric axis so that the alloy, entrained by the rotation of the mold, comes to be pressed against the walls of the mold, thus producing a hollow body whose solification occurs during rotation, and this under the constant effect of centrifugal force.

The axis of rotation of the mold, generally called a shell, can be horizontal vertical, or even oblique.

One can, theoretically, centrifuge a liquid alloy under vacuum, by placing in the same sealed enclosure, and after having evacuated there, a melting furnace and a centrifuge machine, and by transferring the molten metal after melting, from the furnace into the centrifuge shell.

However, this method, valid at the laboratory level, for test pieces, or very small series of pieces, would not apply well to industrial production.

Indeed, more generally in the case of metal centrifugation shells, a mold preparation must precede centrifugal casting.

• 1 - Nettoyer les parois internes de la coquille
• 2 - Préchauffer la coquille pour lui conférer une géographie thermique bien déterminée
• 3 - Poteyer ses parois internes , c'est-à-dire leur appliquer un revêtement conducteur ou isolant , d'épaisseur et de nature très variées.

A classic sequence consists of:

• 1 - Clean the internal walls of the shell
• 2 - Preheat the shell to give it a well-defined thermal geography
• 3 - Poteyer its internal walls, that is to say apply a conductive or insulating coating, of very varied thickness and nature.

This sequence ends shortly before the metal is poured into the shell.

The above operations cannot easily be carried out under vacuum, even by automatic machines, during the melting of the alloy

• 1 . Le nettoyage produit des résidus pulvérulents qui pollueraient l'alliage en fusion .
• 2 . Le préchauffage ne pourrait être fait que par induction et de ce fait peu facile à moduler.
• 3 . Le poteyage nécessite une application des enduits de paroi en phase liquide ou par pulvérisation, et le brouillard qui en résulterait , ainsi que les vapeurs dégagées, viendraient aussi polluer le vide requis pour la fusion du métal.

Indeed :

• 1. Cleaning produces powdery residues which would pollute the molten alloy.
• 2. Preheating could only be done by induction and therefore not easy to modulate.
• 3. Potting requires the application of plaster king in liquid phase or by spraying, and the fog which would result from it, as well as the vapors released, would also pollute the vacuum required for the fusion of the metal.

It is therefore necessary to carry out these preliminary operations on the shells in a normal atmosphere, and then put them under vacuum, without disturbing the environment of the melting furnace so as to make the timing of the centrifugal casting coincide with that of the end of the alloy development

The object of the present invention is to avoid the aforementioned drawbacks by making the manufacturing process easier.

• - une première enceinte étanche munie de sespropres moyens d' accès , d'obturation et de mise sous vide , cette première enceinte contenant le premier matériel ;
• - une seconde enceinte étanche , munie de ses propres moyens d'accès , d'obturation et de mise sous vide , cette seconde enceinte contenant le second matériel ;
• - un conduit étanche reliant la première enceinte à la seconde enceinte , et pourvu d'une vanne d'obturation étanche commandée depuis l'extérieur à l'ouverture et à la fermeture ;
• - et des moyens de transfert permettant , après ouverture de la vanne du conduit étanche , de déverser dans le second matériel de la seconde enceinte , l'alliage liquide reçu du premier matériel de la première enceinte .

The device according to the invention comprises a first material for developing, melting and controlling the centrifugal alloy, as well as a second material for casting the alloy by centrifugal casting, and it is characterized in that it also includes:

• - A first sealed enclosure provided with its own means of access, closure and evacuation, this first enclosure containing the first material;
• - a second sealed enclosure, provided with its own means of access, closure and evacuation, this second enclosure containing the second material;
• - a sealed conduit connecting the first enclosure to the second enclosure, and provided with a sealed shut-off valve controlled from the outside upon opening and closing;
• - And transfer means allowing, after opening the valve of the sealed conduit, to pour into the second material of the second enclosure, the liquid alloy received from the first material of the first enclosure.

• Figures 1 et 2 montrent un dispositif permettant la mise en oeuvre du procédé selon l'invention , pour la centrifugation horizontale de corps métalliques tubulaires.
• Figures 3 et 4 correspondent à deux va- riantes pour la centrifugation horizontale.
• Figure 5 montre , en plan ,une variante où les coquilles de centrifugation sont montées sur un carrousel .
• Figure 6 illustre une autre variante à deux enceintes opposées.
• Figure 7 montre une autre variante dont 1' enceinte contient plusieurs fours.
• Figure 8 illustre une variante supplémentaire pour la centrifugation verticale.

The appended drawing, given by way of nonlimiting example, will allow a better understanding of the characteristics of the invention.

• Figures 1 and 2 show a device for implementing the method according to the invention, for the horizontal centrifugation of tubular metal bodies.
• Figures 3 and 4 correspond to two values laughing for horizontal centrifugation.
• Figure 5 shows, in plan, a variant where the centrifugation shells are mounted on a carousel.
• Figure 6 illustrates another variant with two opposite enclosures.
• Figure 7 shows another variant of which the enclosure contains several ovens.
• Figure 8 illustrates an additional variant for vertical centrifugation.

The device illustrated in Figures 1 and 2 is intended to centrifuge tubular metal parts around a horizontal axis.

For this, use is made, in known manner, of a melting furnace 1, the emptying of which is effected by a chute 2 when it is tilted.

According to the invention, the oven 1 is housed inside a first enclosure 3 in which one can, at will, create a vacuum. By a sealed conduit 4 provided with a sealed closure valve 5, the first enclosure 3 communicates with the second enclosure 6 in which a vacuum can be created, independently of the first enclosure 1.

Enclosures 3 and 6 each have their own opening and access device, allowing equipment, materials or people to enter it, if necessary.

Enclosure 3 is equipped with all the equipment for developing, melting and controlling the alloy to be centrifuged.

In enclosure 6 there is a mechanical device for driving a centrifuge shell 7. This mechanism, known in itself, can be constituted by four rollers 8, at least one of which is the author, the whole having been designed to be able to operate under vacuum.

The general reference 9 designates the device and the material necessary for cleaning, preheating, poteying a horizontal centrifugation shell. J In enclosure 3 there is also a chute 10, carried by a translation device capable of operating under vacuum, so that the pouring tube 11 of this chute can come, after opening the valve 5, to protrude into the enclosure 6, while its receptacle takes place under the pouring spout 2 of the furnace 1 (position in solid lines, in FIG. 1). The horizontal translation of the chute 10 takes place between this position in solid lines and that shown in FIG. 1, in broken lines,

The operation is as follows:

Phase 1

• - enclosure 3 is open. The solid materials are loaded into the furnace 1;
• - the enclosure 6 is open;
• - the centrifugation shell is placed on the device 9.

Phase 2

• - we close enclosure 3
• - the valve 5 is closed
• - there is a vacuum in enclosure 3
• - we apply the power to oven 1, to melt the metal
• - Preparing the contrifugation shell on the device 9 (cleaning, preheating, poteyage).

Phase 3.

• - a little before the material is ready to be poured, the centrifuge shell 7 is introduced into the enclosure 6 and it is placed on the device intended to set it in rotation (rollers 8)
• - we close enclosure 6
• - there is a vacuum in enclosure 6.

Phase 4

• - the valve 5 is opened, which makes the two empty chambers 3 and 6 communicate
• - It causes the displacement of the chute 10 so that its pouring spout 11 is introduced into the centrifuge shell, while the receptacle formed by its funnel is placed under the emptying spout 2 of the fourl.

This chute 11 will have been electrically preheated during the melting of the metal in the furnace 1

Phase 5

• - the shell 7 is put in rotation, if the casting is to be carried out in a rotating shell (In some cases, in fact, the casting is carried out in a fixed shell which is put into rotation after filling)
• - the oven 1 is emptied into the chute 10 which passes the liquid alloy through the shell 7
• - The metal alloy which solidifies under vacuum is thus centrifuged.

Phase 6

After solidification, two cases can occur:

A - or else the furnace 1 still contains elaborate and molten-vacuum metal

• - the chute 11 is brought back into the enclosure 3
• - the valve 5 is closed
• - we let the air enter the enclosure 6 and we open it
• - the shell 7 is extracted from the enclosure 6 with an appropriate device
• - the centrifuged part is extracted from the shell 7
• - The cycle concerning the shell 7 is restarted with the same shell 7 until the liquid metal in the oven is used up;

B - or else the entire load contained in the oven 1 has been transferred to the centrifuge shell 7

• - if necessary, the chute 11 is brought back into the enclosure 3
• - the air is allowed to enter the two chambers 3 and 6
• - the shell 7 is extracted from the enclosure 6
• - the centrifuged part is extracted from the shell 7.

It recomn _e nce then the whole cycle (six phases above) to make a new part.

In another variant, around a melting enclosure 1 containing one or more ovens, several centrifuging enclosures which can be intended to receive the liquid metal produced under vacuum in horizontal or vertical centrifuge machines are placed.

There is shown in Figure 3 a variant where two speakers 6 are located on the same side of the girdle 3 and each contain a horizontal centrifuge machine.

In the case of FIG. 4, two chambers 6 are diametrically opposite on either side of the chamber 3, and each contain a horizontal centrifuge machine.

FIG. 5 shows a variant in which the device comprises a feed carousel 12, making it possible to present the shells 7 one by one in front of the second enclosure 6.

If the oven contains enough alloys to centrifuge several pieces under vacuum, several identical centrifuge shells 7 can be used which alternately undergo the various treatments prior to centrifugal casting, cooling, cleaning, preheating, vacuum coating in the second enclosure 6 .

A carrousel 12 has thus been formed where each position of a shell 7 corresponds to an operation of the above range or else a series of identical waiting devices, on each of which each shell 7 is the subject of the following range operations before and after vacuuming.

In the variant of FIG. 6, two chambers 6 and 13 are diametrically opposite, but of different natures: they contain, one a horizontal centrifuge machine, the other a vertical centrifuge machine, which gives the installation a wide range of possibilities.

In a variant illustrated in FIG. 7, the enclosure 3 contains several ovens such as 1 and 21, of identical or different capacities, in order to have either an increased metal capacity or a great flexibility, to make vary the mass of metal used.

The ovens 1, 21 are arranged such that their pouring spout 2, 22, etc. allows the simultaneous or successive emptying thereof, in the same chute 10 in the working position.

One of the provisions of this variant consists in supplying the two ovens 1 and 21 with different alloys and thus producing by centrifugation a bi-metallic tube by centrifuging successively the two alloys; the first then constitutes the external envelope of the bi-metallic tube, the second the internal coating.

In another variant (FIG. 8), a completely similar assembly has been shown, different only by the fact that the second enclosure 6 contains a vertical centrifuge machine 14.

Here, the shell is also prepared outside the enclosure 3, during the melting of the alloy, then it is introduced into the enclosure 6, fixed to the plate of the machine 14 by a quick-locking device of known type , and surmounted by a preheated pouring funnel 15.

After evacuating the enclosure 6, and opening the valve 5, the chute 10 is moved as for horizontal centrifugation, so that its pouring spout 11 comes above the funnel 15, and the alloy is centrifuged under vacuum as soon as the oven 1 is tipped over.

The different working methods are, in this variant, quite comparable to those involved in the horizontal process.

According to yet another variant, it is possible to have around a melting enclosure 3, containing one or more ovens 1, 21, etc., several centrifugation enclosures 6, which can be intended to receive the liquid metal produced under vacuum in horizontal or vertical centrifuge machines.

Claims (12)

1 -Centrifugal casting device comprising a first material for developing, melting and controlling the centrifugal alloy, as well as a second material for casting the alloy by centrifugal casting, and characterized in that it comprises otherwise : - A first sealed enclosure (3) provided with its own means of access, closure and evacuation, this first enclosure containing the first material (1), (2); - a second sealed enclosure (6) provided with its own means of access, closure and evacuation, this second enclosure containing the second material (7), (8); - A sealed duct (4) connecting the first enclosure (3) to the second enclosure (6), and provided with a shut-off valve (5) controlled from the outside when opening and closing; - And transfer means (10), (11), allowing, after opening the valve (5) of the sealed conduit, to pour into the second material of the second enclosure (6), the liquid alloy received from the first material of the first enclosure (3). 2 - Device according to claim 1, characterized in that the first material comprises, inside the first sealed enclosure (3), a melting furnace (1), the emptying of which is effected by a chute (2) when you tip it 3 - Device according to claim 1, characterized in that the second material comprises, inside the second sealed enclosure (6), a mechanical roller device (8), for driving a centrifuge shell ( 7). 4 - Device according to claim 1, characterized in that, in the enclosure (3), there is also a chute (10), carried by a translation device which can operate under vacuum, so that the pouring tube (11) of this chute can come, after opening the valve (5), protrude into the enclosure (6), while its receptacle takes place under the pouring spout (2) of the oven (1). 5 - Device according to any one of the preceding claims, characterized in that around the melting chamber (3) are arranged several centrifuge chambers (6) which can be intended to receive the liquid metal produced under vacuum in horizontal or vertical centrifuge machines. , each enclosure (6) communicating with the enclosure (3) by a conduit (4) and a sealed valve (5). 6 - Device according to claim 5, characterized in that two chambers (6) are located on the same side of the chamber (3) and each contain a horizontal centrifuge machine (FIG. 3). 7 - Device according to any one of claims 1 to 5, characterized in that two enclosures (6) are diametrically opposite, on either side of the enclosure (3) and each contain a horizontal centrifuge machine (Figure 4). 8 - Device according to any one of claims 1 to 5, characterized in that it comprises a feed carousel (12), allowing to present one by one the shells (7) in front of the second enclosure (6). (figure 5). 9 - Device according to any one of claims 1 to 5, characterized in that two chambers (6) and (13) are diametrically opposite, but of different natures: they contain, one (6) a horizontal centrifuge machine , the other (13), a vertical centrifuge machine, which gives the installation a wide range of possibilities (Figure 6). 10 - Device according to any one of claims 1 to 5, characterized in that the enclosure (3) contains several ovens such as (1) and (21), of identical or different capacities, in order to have either increased capacity of metal, or great flexibility, to vary the mass of metal used (Figure 7). 11 - Device according to any one of the preceding claims, characterized in that the second enclosure (6) contains a vertical centrifuge machine ( ₁₄ ). 12 - Process for the centrifugal casting of metal parts by implementing the device according to 1 "any one of the preceding claims, characterized in that it comprises in combination, the following phases: Phase 1 - the enclosure (3) is open. Solid materials are loaded into the oven (1); - the enclosure (6) is open; - the centrifuge shell is placed on the device (9). Phase 2 - the enclosure is closed (3) - the valve (5) is closed - there is a vacuum in the enclosure (3) - we apply the power to the oven (1), to melt the metal - Preparing the centrifugation shell on the device (9) (cleaning, preheating, potage). Phase 3 - a little before the material is ready to be poured, the centrifuge shell (7) is introduced into the enclosure (6) and it is placed on the device intended to set it in rotation (rollers (8) - the enclosure is closed (6) - there is a vacuum in the enclosure (6). Phase 4 - the valve (5) is opened, which makes the two empty enclosures (3) and (6) communicate - It causes the displacement of the chute (10), so that its pouring spout (11) is introduced into the centrifuge shell, while the receptacle formed by its funnel is placed under the emptying spout (2) of the oven (1)
This chute (11) will have been electrically preheated during the melting of the metal in the oven (1). Phase 5 - the shell (7) is put in rotation, if the casting is to be carried out in a rotating shell (In certain cases, indeed, the casting takes place in a fixed shell, which is rotated after filling) - the oven (1) is emptied into the chute (10) which passes the liquid alloy through the shell (7) - The metal alloy which solidifies under vacuum is thus centrifuged.

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