AU2019407845B2

AU2019407845B2 - Anode assembly and associated manufacturing method

Info

Publication number: AU2019407845B2
Application number: AU2019407845A
Authority: AU
Inventors: Jean-Louis ABEILLE
Original assignee: Rio Tinto Alcan International Ltd
Current assignee: Rio Tinto Alcan International Ltd
Priority date: 2018-12-20
Filing date: 2019-12-12
Publication date: 2024-09-26
Anticipated expiration: 2039-12-12
Also published as: AU2019407845A1; PY19106395A; EP3899105A4; WO2020124209A1; EP3899105A1; AR117450A1; CN113195792A; CA3122504A1; FR3090699A1; FR3090699B1; CN113195792B

Abstract

The present invention relates to a method for manufacturing (100) an anode assembly (10) which is intended for the vessels for producing aluminium by electrolysis, the anode assembly (10) comprising an anode rod (1), a metal block (2) which is secured to one (11) of the ends of the anode rod (1), the metal block (2) being able to expand in a longitudinal direction under the effect of heat, and a carbon-containing anode (3) including a recess (30), in which the metal block (2) is received for sealing the metal block (2) to the carbon-containing anode (3), a sealed zone (41) which is filled with sealing material extending between the metal block (2) and the carbon-containing anode (3), characterised in that the method (100) comprises a step (102) of forming at least a first cavity (42) inside the carbon-containing anode (3), the at least first cavity (42) forming with the recess (30) a first zone of reduced thickness (43) inside the carbon-containing anode (3), the first zone of reduced thickness (43) being capable of becoming deformed or fracturing under the effect of the expansion of the metal block (2) in the longitudinal direction.

Description

Description Title: Anode assembly and associated manufacturing method

Technical Field

This invention relates to an anode assembly for cells designed to produce aluminum by electrolysis, as well as a manufacturing method such an anode assembly.

It is particularly suitable for electrolytic cells with pre-baked anodes.

Background of the Invention

Aluminum is essentially produced by electrolysis of alumina dissolved in a cryolite bath. The electrolytic cell that allows this operation is constituted by a steel box and lined internally with refractory insulating products.

A cathode formed of carbonaceous blocks is placed in the box. It is surmounted by an anode or a plurality of carbonaceous anodes, or carbonaceous anode blocks, plunging into the cryolite bath. This (or these) carbonaceous anode(s) is (are) oxidized(s) gradually by the oxygen from the decomposition of the alumina.

The passage of the current is produced from the anode to the cathode through the cryolite bath, maintained in the liquid state by the Joule effect.

The usual operating temperatures of a cell being between 930 and 980°C, the aluminum produced is liquid and is deposited by gravity on the cathode. Periodically, the aluminum produced, or a part of the aluminum produced, is extracted using a casting ladle and transferred into foundry furnaces. Once the anodes are spent, they are replaced by new anodes. To allow handling and its power supply, each anode is generally associated with a structure to form an anode assembly. This structure is generally composed of: - an anode rod of material with high electrical conductivity, such as aluminum or copper,

and - a means of attachment made of a material that is resistant to the elevated temperatures

encountered when using the anode, such as steel. The means of attachment generally comprise a multipode shaped as an integral crossbar on the base of the rod associated with a plurality of advantageously cylindrical blocks whose axis is parallel to the rod.

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The blocks are partially introduced inside recesses made on the upper surface of the anode, and the gaps existing between the blocks and the recesses are filled by casting a molten metal, typically cast iron. The metal cylinders thus produced make it possible to ensure

(44682068_1):KRM good mechanical fastening and a good electrical connection between the rod and the anode.

However, it has been found in the prior art that the presence of blocks induce an ohmic drop in the connection of the anode, as well as thermal losses through the anode assembly.

This is why document WO 2012/100340 proposes an anode assembly in which the assembly composed of the crossbar and the blocks is replaced by a longitudinal connection bar. When sealing, this connecting bar is introduced into a longitudinal groove made on the upper surface of the anode. Molten cast iron is then deposited at the periphery of the connection bar to fill the space between the connection bar and the groove.

This solution makes it possible to improve the distribution of currents within the anode, to reduce the ohmic drop at the contact between the carbon and cast iron and to limit heat losses, as had already been taught in document FR 1,326,481 which proposed an identical solution to WO 2012/100340.

However, if the anode assemblies of the prior art, preferably included cylindrical blocks, it was to chiefly limit the deterioration risks of the anode due to the expansion undergone by the means of attachment during the introduction of the anode into the cryolite bath whose temperature is between 930 and 980°C.

Indeed, unlike cylindrical blocks whose expansion induces the application of a radial thermal expansion force on the anode, the thermal expansion of a metal bar induces the application of transverse and longitudinal forces on the anode which are likely to crack it.

No solution to this cracking problem is proposed in FR 1,326,481 or in WO 2012/100340.

In document WO 2015/110906, a solution is proposed to this problem of cracking. This solution consists of providing at least one space with no sealing material at one of the longitudinal ends of the connecting bar, said space being advantageously able to be lined with a compressible packing material, such as refractory fiber. Thus, during the expansion of the connection bar, the refractory fiber absorbs the forces applied longitudinally by it, thus preventing a crack in the anode under the effect of said forces. However, this solution has the disadvantage of requiring a manual placement of the refractory fiber before the casting the sealing material. This therefore exaggerates the costs and manufacturing times. In addition, once the electrolysis is carried out, the refractory fiber must be removed from the anode assembly to be able to recycle the carbon. This operation also increases costs and recycling times.

One purpose of this invention is to propose a manufacturing method that less costly and less complex than that proposed in document WO 2015/110906. This manufacturing method for forming an anode assembly having a lower risk of the anode cracking under the effect of the thermal expansion of the connecting bar.

Another purpose of this invention is to provide an anode assembly that is obtainable by said manufacturing method.

Summary of the Invention

Accordingly, in an aspect, the present invention proposes a manufacturing method an anode assembly for the cells for producing aluminum by electrolysis, the anode assembly being of the type comprising an anode rod, a metal block integral with one of the ends of the anode rod, said metal block being able to expand in a longitudinal direction under the effect of heat, and a carbonaceous anode including a recess in which is housed the metal block for sealing the metal block at the carbonaceous anode, a sealed area filled with sealing material extending between the metal block and the carbonaceous anode, wherein the method comprises a step of forming at least afirst cavity inside the carbonaceous anode, said at least first cavity that forms with said recess a first zone of lesser thickness inside the carbonaceous anode, said first zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block, and wherein said first zone of lesser thickness is adjacent to a transverse internal side wall of said recess. Thus configured, the manufacturing method according to the invention makes it possible to form an anode assembly presenting less risk of cracking of the carbonaceous anode under the effect of the expansion of the metal block.

Indeed, a part of the forces applied to the anode by the metal block during its expansion in the longitudinal direction is absorbed by the area of reduced thickness and the cavity.

Advantageously, the method of the invention may further comprise a step of forming at least a second cavity inside the carbonaceous anode, said at least second cavity that forms with said recess a second zone of lesser thickness inside the carbonaceous anode, said second zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block. In an alternative embodiment, the metal block has a substantially a parallelepiped shape specifically defined by four longitudinal surfaces connected by two transverse surfaces, said at least first zone of lesser thickness and respectively, said at least second zone of lesser thickness, being placed parallely to one of said transverse surfaces and being separated therefrom by the sealed area.

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In the case of an anode assembly comprising two zones of lesser thickness, each zone of lesser thickness will advantageously extend to a respective longitudinal end of the metal block. The areas of lesser thickness will then be distributed on either side of the anode rod, which on the one hand, will allow a better distribution of the intensity of forces during the expansion, and on the other hand, a better balance of the masses of the anode assembly.

In a variant of the embodiment, the step of forming said at least first cavity, respectively of said at least second cavity, may comprise a step of placing an insert in a mold intended to form the carbonaceous anode so as to define at least one projecting part inside the mold, said projecting part being designed to form said at leastfirst cavity and respectively, said at least second cavity.

In another variant of the embodiment, the step to form said at leastfirst cavity, respectively of said at least second cavity, may comprise a step of machining the carbonaceous anode.

In another aspect, the present invention provides an anode assembly for cells to produce aluminum by electrolysis, the anode assembly comprising an anode rod, a metal block integral with one of the ends of the anode rod, said metal block being able to expand in a longitudinal direction under the effect of heat, and a carbonaceous anode including a recess in which is housed the metal block for sealing the metal block at the carbonaceous anode, a sealed area filled with sealing material extending between the metal block and the carbonaceous anode, wherein the carbonaceous anode comprises at least a first cavity, said at least first cavity that forms with said recess a first zone of lesser thickness inside the carbonaceous anode, said first zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block, and wherein said first zone of lesser thickness is adjacent to a transverse internal side wall of said recess. Preferred but non-limiting aspects of the anode assembly are as follows: - the carbonaceous anode comprises at least a second cavity, said at least second cavity that forms with said recess a second zone of lesser thickness inside the carbonaceous anode, said second zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block; - the metal block has a substantially parallelepiped shape defined in particular by four

longitudinal surfaces connected by two transverse surfaces, said at least first zone of lesser thickness, and respectively, said at least second zone of lesser thickness, being placed parallely to one of said transverse surfaces and being separated therefrom by the sealed area;

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4a

the first, respectively the second cavity, protrudes transversely and vertically from a longitudinal projection of a transverse internal side wall of the recess, the excess being preferably less than 5 cm; - the first, respectively the second, zone of lesser thickness has a substantially flat profile and is oriented perpendicularly to said longitudinal direction;

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- the first, respectively the second, zone of lesser thickness has a three-part profile, i.e., a central part surrounded by two end parts, said central part being substantially flat and oriented perpendicularly to said longitudinal direction and said end parts being oriented obliquely with respect to said central part; - the first, respectively the second, zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a biconvex profile, and wherein the first, respectively the second, zone of lesser thickness is less thick at said attachment zone; - the first, respectively the second, zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a flat profile, and wherein the first, respectively the second, zone of lesser thickness is less thick at said attachment zone; - the first, respectively the second, zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a flat-biconvex profile, and wherein the first, respectively the second, zone of lesser thickness is less thick at said attachment zone.

Brief Description of the Figures

Other advantages and characteristics of the anode assembly and its associated manufacturing method will emerge from the following description of several alternative embodiments, given by way of non-limiting examples, from the appended drawings in which:

[Fig. 1] Figure 1 is a view in perspective of an anode assembly in accordance with a first variant of an embodiment of the invention.

[Fig 2] Figure 2 is a view in perspective of the metal block attached to the anode rod prior to its integration into the anode assembly shown in Figure 1,

[Fig 3] Figure 3 is a view in perspective of the carbonaceous anode used for manufacturing the anode assembly shown in Figure 1,

[Fig. 4] Figure 4 is a top view of an anode assembly in accordance with a second variant of an embodiment of the invention.

[Fig. 5] Figure 5 is a cross-sectional view along CC'of the anode assembly represented in Figure 4,

[Fig. 6] Figures 6a-6e are partial views, from above of several variants of embodiments of the invention,

[Fig. 7] Figure 7 is a block diagram of a manufacturing method for an anode assembly according to the invention.

Detailed Description

An example of a manufacturing method for an anode assembly as well as examples of anode assemblies obtained from the process will now be described. In these different figures, the equivalent elements bear the same numerical references. In the rest of the text, the terms "sidesurface", "lowersurface", "upper surface", "side walls" and "bottom"will be used with reference to an anode rod extending along A-A' axis

. The reader will appreciate that within the context of this invention, the following is meant: - "lowersurface"or "upper surface", a surface extending in a plane perpendicular to the A-A' axis , the upper surface of a given piece being closer to the anode rod than to the lower surface,

- "surface/side wall"means a surface/wall extending in a plane parallel to the A-A' axis of the anode rod,

- "surface/longitudinal wall"means a surface/wall extending parallel to a longitudinal axis of a longitudinal object (for example a recess or a metal block),

- "surface/transverse wall", means a surface/wall extending perpendicularly to a longitudinal axis of a longitudinal object,

- "longitudinal direction"or "longitudinally", a direction parallel to the longitudinal axis of a longitudinal object (for example a recess or a metal block),

- "outer wall"or "inner wall"of a cavity, a wall that is the farthest, respectively, the least remote, from the A-A' axis.

Figure 1 illustrates an example of an anode assembly according to the invention. With reference to Figures 1 to 3, the anode assembly 10 comprises an anode rod 1, a metal block 2, and a carbonaceous anode 3.

The anode rod 1 is made of an electrically conductive material. It extends along the A-A' axis. The anode rod is of a type commonly known to those skilled in the art and will not be described in more detail below.

The metal block 2 forms a means of attachment. The metal block 2 is in an electrically conductive material capable of withstanding the high temperatures of use of the anode assembly. For example, the metal block is made of steel.

The dimensions of the metal block 2 may be as follows:

- length L between 80 and 200 centimeters,

- width I and height h between 5 and 50 centimeters.

In all cases, the length L is at least two times greater than the width I of the metal block 2.

The metal block 2 is integral with the anode rod 1 at one of its ends 11 and extends along a longitudinal B-B'axis perpendicular to the A-A'axis. The metal block 2 comprises an upper surface 23 in contact with the anode rod 1, a lower surface 24 opposite the upper surface 23, two longitudinal side surfaces 22 and two transverse side surfaces 21. The metal block 2 is for example a bar, possibly having a rectangular parallelepiped shape, and may comprise teeth, in particular of a rounded shape, on its side surfaces 21, 22 and/or its lower surface 24.

The anode 3 is an anode block of pre-baked carbon material whose composition and general form are known to those skilled in the art and will not be described in more detail later. The upper surface of the anode 3 has a recess 30 in which is housed the metal block 2.

Advantageously, the recess 30 may be of a shape complementary to that of the metal block 2. In this case, the recess 30 has longitudinal internal side walls 32, transverse internal side walls 31, and a bottom 34.

The width I' of the recess or groove is greater than the width I of the metal block 2 to allow the insertion of the metal block 2.

The anode assembly further comprises sealed areas filled with a sealing material 41. The sealed zones extend between the longitudinal internal walls 32 of the recess 30, and the longitudinal side surfaces 22 of the metal block 2.

In the context of this invention, the term "sealing material" is intended to mean a material allowing the formation of a rigid and conductive connection between an anode and a metal block, this connection being typically provided by cast metal between the metal block and the anode, such as cast iron, or a conductive paste.

As shown in Figure 1, the sealing material 41 coats all the side surfaces 21, 22 of the metal block 2. The forces applied longitudinally by the metal block 2 during its expansion will therefore be transmitted integrally, via the sealed zones 41 adjacent to the transverse side surfaces 21 of the metal block 2, to the anode 3.

Indeed, we must remember, that as a guide, the steel metal block having a length equal to 1 meter can undergo a longitudinal expansion of up to 2 centimeters at 1000°C. This longitudinal expansion could potentially induce a very significant deterioration of the anode 3 (cracks, explosions, etc.).

In order to avoid such deterioration of the anode 3 under the effect of said longitudinal forces, the anode 3 is advantageously provided with a pair of cavities 42 placed on either side of the recess 30 along the longitudinal B-B' axis, each of the cavities 42 being located near a sealed zone 41 adjacent to one of the transverse side surfaces 21 of the metal block 2. Thus placed, each of the cavities 42, together with the recess 30, form a zone of lesser thickness 43 in the anode 3, said zone of lesser thickness 43 being between said sealed zone 41 and said cavity 42. This zone of lesser thickness 43 will in particular be configured to be able to deform or fracture under the effect of the forces applied longitudinally by the metal block 2.

The thickness of the zone of least thickness 43 is advantageously less than 5 cm and preferably between 0.5 and 3 cm to be able to deform or fracture without propagation of cracks in the rest of the anode. The cavity 42 will advantageously have a thickness greater than 0.5 cm and preferably greater than 1 cm in order to be able to absorb the deformation of the thickness of the zone of lesser thickness 43 caused by the expansion of the metal block 2.

Thus, during the expansion of the metal block 2, the forces applied longitudinally by the metal block 2 will advantageously be transmitted first to the areas of lesser thickness 43, which will result in either deformation or fracturing of said areas of lesser thickness 43. Because the remainder of the anode 3, in particular the parts of the anode 3 between one of the side edges 33 of the anode 3 and the outer wall of the cavity 42 closest to the latter, is not directly subjected to all the forces applied longitudinally by the metal block, the risk of deterioration is considerably lessened.

In reference to Figures 4 and 5, another embodiment of the anode assembly is illustrated, respectively in top view and in a cross-sectional view along C-C'.

In this variant embodiment, the anode 3 has only one cavity 42 which with the recess 30, defines a single zone of lesser thickness 43. This zone of lesser thickness 43 will, however, be sufficient to limit the risk of damage to the entire anode 3.

Regardless of the embodiment, anode 3 comprises at least one cavity 42 spaced from the recess 30 so that a zone of lesser thickness 43 of the anode 3 is formed between the at least one cavity 42 and said recess 30._Anode 3 therefore comprises at least one zone of lesser thickness 43._The zone of lesser thickness 43 is a structure of the anode 3 which is able to deform or fracture under the effect of the expansion of the metal block, for example in the longitudinal direction.

As can be seen in Figures 4 and 5, the cavity 42 extends transversely and vertically beyond a longitudinal projection of the internal transverse side wall 31. Such a configuration allows cracks within the cavity 42 to fade, extending from the transverse internal side wall in a mainly longitudinal direction slightly away from the C-C'axis. The excess is advantageously less than 5 cm and preferably less than 3 cm so as to avoid weakening the anode 3 and disturbing the distribution of the current to the entire lower surface of the anode 3.

The shape of the zone of lesser thickness 43, the cavity 42 and the recess 30 may vary according to various parameters, such as, in particular, the constituent material, the dimensions and/or the shape of the anode 3 and/or the metal block 2. In particular, in certain embodiments, the shape of the zone of least thickness 43 may comprise at least one fracturing interface of the anode 3 configured so that the zone of lesser thickness 43 is able to fracture at the said at least one fracturing interface, for example under the effect of a given stress resulting from the expansion of the metal block. Such a fracturing interface could abut a concave surface of the recess 30 or the cavity 42. This concave surface could be curved, that is to say defining a curve (as for example at the ends of the cavity 42 of Figure 6a). The curve of such a concave surface could be configured to a greater or lesser extent so that the effect of the concentration of stress in the area of least thickness 43 may be of greater or lesser importance. The concave surface could also be angulated, i.e., defining an angle between two parts of said concave surface (as for example at the ends of the cavity 42 of Figure 6b). The angle of such a concave surface could be configured to a greater or lesser extent so that the effect of the concentration of stress in the area of least thickness 43 may be of greater or lesser importance.

With reference to Figures 6a to 6e, there are shown several advantageous examples of anode 3 that can be used within the anode assembly of this invention.

In the example shown in Figure 6a, the zone of smaller thickness 43 has a substantially flat profile and is perpendicularly oriented towards the B-B' axis of the metal block 2. The transverse internal side wall 31 of the recess 30 adjacent to the zone of lesser thickness 43 and the inner and outer walls of the corresponding cavity 42 are, in this case, of a straight profile and perpendicular to the B-B' axis.

In the example shown in Figure 6b, the zone of lesser thickness 43 has a profile in two parts, i.e., a first part 434 and a second part 435 connected to each other at a attachment zone 430. Each of the parts 434, 435 has a biconvex profile, and the zone of lesser thickness 43 has a lesser thickness at the attachment zone 430. The internal transverse side wall 31 of the recess 30 adjacent to the zone of lesser thickness 43 is, in this case, of a curved profile, complementary to that of the zone of lesser thickness 43, and the inner wall of the corresponding cavity 42 also has a curved profile, complementary to that of the zone of lesser thickness 43.

In the example shown in Figure 6c, the zone of lesser thickness 43 has a two-part profile, i.e., a first part 436 and a second part 437 connected to each other at the attachment zone

430. Each of the parts 436, 437 has a substantially flat profile, and the zone of lesser thickness 43 has a lesser thickness at the attachment zone 430. The internal transverse side wall 31 of the recess 30 adjacent to the zone of lesser thickness 43 and the inner wall of the corresponding cavity 42 are, in this case, substantially straight in profile and perpendicular to the B-B' axis, except for their respective areas which are aligned with the attachment zone 430, for which the profile is substantially triangular.

In the example shown in Figure 6d, the zone of lesser thickness 43 has a three-part profile, i.e., a central part 431 surrounded by two end parts 432 and 433. The central part 431 is substantially flat and is oriented perpendicularly to the B-B'axis, and the end parts 432 and 433 are oriented obliquely with respect to the central part 431. The transverse internal side wall 31 of the recess 30 adjacent to the zone of lesser thickness 43 has, in this case, a straight profile that is perpendicular to the B-B' axis, and the inner and outer walls of the corresponding cavity 42 possess a substantially complementary profile to that of the area of lesser thickness 43.

In the example shown in Figure 6e, the zone of lesser thickness 43 has a two-part profile, i.e., a first part 438 and a second part 439 connected to each other at the attachment zone 430. Each of the parts 438, 439 has a flat-biconvex profile, and the zone of lesser thickness 43 has a lesser thickness at the attachment zone 430. The internal transverse side wall 31 of the recess 30 adjacent to the zone of lesser thickness 43 is, in this case, of a curved profile, complementary to that of the zone of lesser thickness 43, and the inner wall of the corresponding cavity 42 also has a curved profile, complementary to that of the zone of lesser thickness 43. The cavity 42 therefore has, in this case, a gull-wing profile.

An example of a manufacturing method for an anode assembly according to the invention will now be described with reference to Figure 7.

This manufacturing method 100 can be applied to form an anode assembly 10, the anode 3 of which has a single zone of lesser thickness 43 adjacent to one of the internal transverse side walls 31 of the recess 30.

As a variant, this manufacturing method 100 may also be applied to form an anode assembly 10, the anode 3 of which has two zones of lesser thickness 43 placed on either side of a recess 30, each of the zones of lesser thickness 43 are adjacent to one of the transverse internal side walls 31 of the recess 30.

In a first step 101 of the manufacturing method 100, a metal block 2 secured to an anode rod 1 is provided.

In a second step 102, a carbonaceous anode 3 provided with a recess 30 and at least one cavity 42 is formed. The second step 102 may, in a first variant of the method, comprise, prior to a molding step of the carbonaceous anode 3, a step of placing an insert in a mold intended to form the carbonaceous anode 3 so as to define at least one projecting part inside the mold, said projecting part being intended to form said at least one cavity 42.

In a second variant of the method, the second step 102 may comprise a step of molding the carbonaceous anode 3 followed by a step of machining the carbonaceous anode 3 to form said at least one cavity 42.

In the third step 103, the metal block 2 is introduced inside the recess 30 and the gap separating the metal block 2 from the anode 3 is filled with a sealing material so as to form the sealed zone 41.

Thus, with a method easily adapted for use in industry, an anode assembly 10 according to this invention is obtained. Thus formed, this anode assembly 10 makes it possible to limit the risks of cracks and / or bursting of the anode 3 when it is introduced into a cryolite bath.

Claims

1. A manufacturing method of an anode assembly designed for cells for the production of aluminum by electrolysis, the anode assembly being of the type comprising an anode rod, a metal block integral with one of the ends of the anode rod, said metal block being able to expand in a longitudinal direction under the effect of heat, and a carbonaceous anode including a recess in which is housed the metal block for sealing the metal block at the carbonaceous anode, a sealed area filled with sealing material extending between the metal block and the carbonaceous anode, wherein the method comprises a step of forming at least a first cavity inside the carbonaceous anode, said at least first cavity that forms with said recess a first zone of lesser thickness inside the carbonaceous anode, said first zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block, and wherein said first zone of lesser thickness is adjacent to a transverse internal side wall of said recess.

2. A manufacturing method according to Claim 1, further comprising a step of forming at least a second cavity inside the carbonaceous anode, said at least second cavity that forms with said recess a second zone of lesser thickness inside the carbonaceous anode, said second zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block.

3. A manufacturing method according to Claim 1 or 2, wherein the metal block has a substantially parallelepiped shape defined in particular by four longitudinal surfaces connected by two transverse surfaces, said at least first zone of lesser thickness, being arranged parallel to one of said transverse surfaces and being separated therefrom by the sealed area.

4. A manufacturing method according to Claim 1 or 3, wherein the forming step of said at least first cavity comprises a step of placing an insert in a mold intended to form the carbonaceous anode so as to define at least one projecting part inside the mold, said projecting part being designed to form said at least first cavity.

5. A manufacturing method according to Claim 1 or 3, wherein the forming step of said at least first cavity comprises a machining step of the carbonaceous anode.

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6. A manufacturing method according to Claim 1 or 5, wherein said at least first cavity is formed so as to protrude transversely and vertically from a longitudinal projection of the transverse internal side wall of the recess.

7. An anode assembly designed for cells for the production of aluminum by electrolysis, the anode assembly comprising an anode rod, a metal block integral with one of the ends of the anode rod, said metal block being able to expand in a longitudinal direction under the effect of heat, and a carbonaceous anode including a recess in which is housed the metal block for sealing the metal block at the carbonaceous anode, a sealed areafilled with sealing material extending between the metal block and the carbonaceous anode, wherein the carbonaceous anode comprises at least a first cavity, said at least first cavity that forms with said recess a first zone of lesser thickness inside the carbonaceous anode, said first zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block, and wherein said first zone of lesser thickness is adjacent to a transverse internal side wall of said recess.

8. An anode assembly according to Claim 7, wherein the carbonaceous anode comprises at least a second cavity, said at least second cavity that forms with said recess a second zone of lesser thickness inside the carbonaceous anode, said second zone of lesser thickness being able to deform or fracture under the effect of the expansion in the longitudinal direction of the metal block.

9. An anode assembly according to Claim 7 or 8, wherein the metal block has a substantially parallelepiped shape defined in particular by four longitudinal surfaces connected by two transverse surfaces, said at least first zone of lesser thickness, being arranged parallel to one of said transverse surfaces and being separated therefrom by the sealed area.

10. An anode assembly according to any one of Claims 7 to 9, wherein the first zone of lesser thickness has a substantially flat profile and is oriented perpendicularly to said longitudinal direction.

11. An anode assembly according to any one of Claims 7 to 9, wherein the first zone of lesser thickness has a three-part profile, i.e., a central part surrounded by two end parts, said central

(44682068_1):KRM part being substantially flat and oriented perpendicularly to said longitudinal direction and said end parts being oriented obliquely with respect to said central part.

12. An anode assembly according to any one of Claims 7 to 9, wherein the first zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a biconvex profile, and wherein the first zone of lesser thickness is less thick at said attachment zone.

13. An anode assembly according to any one of Claims 7 to 9, wherein the first zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a substantially flat profile, and wherein the first, respectively the second, zone of lesser thickness is less thick at said attachment zone.

14. An anode assembly according to any one of Claims 7 to 9, wherein the first zone of lesser thickness has a two-part profile, i.e., a first part and a second part connected to each other at an attachment zone, each of said first and second parts having a biconvex profile, and wherein the first, respectively the second, zone of lesser thickness is less thick at said attachment zone.

15. An anode assembly according to any one of Claims 7 to 14, wherein said at least first cavity protrudes transversely and vertically from a longitudinal projection of the transverse internal side wall of the recess.

16. An anode assembly according to Claim 15, wherein said at least first cavity protrudes from said longitudinal projection of said transverse internal side wall of said recess by less than 5 cm.

17. A manufacturing method according to Claim 6, wherein said at least first cavity is formed to protrude from said longitudinal projection of said transverse internal side wall of said recess by less than 5 cm.

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[Fig 1]

A

10 1 41 23 2 3

42 42 43 33

43 33

11 41

A'

[Fig 2]

A

1 21 11 23 21 B' B H

22 24

A'

[Fig 3]

32 31 30 32 31 3

33

34

[Fig 4]

42

-3-

-2-

C' C

41 43

[Fig 5]

42

-2-

-3-

41 43

B'

Fig. 6e

438 42

439

B' B

431

Fig. 6d

42 433

432

B' B

430

Fig. 6c

42

436

437

B B'

Fig. 6b

434 42

430 B' B 435

Fig. 6a

42

43

30 B

[Fig 7]

-101-

-102- 100