WO2016108696A1

WO2016108696A1 - Anode hanger (anode yoke)

Info

Publication number: WO2016108696A1
Application number: PCT/NO2015/050249
Authority: WO
Inventors: Nils SANDE
Original assignee: Storvik As
Priority date: 2014-12-30
Filing date: 2015-12-17
Publication date: 2016-07-07
Also published as: NO20141570A1; NO341533B1

Abstract

An anode hanger for an electrode of electrolysis cells for production of aluminium, comprises an inner portion of copper material having a first surface and an outer portion of steel material covering and bonded to a substantial part of said first surface of the inner portion. An interface between said inner portion and said outer portion provides a substantially continuous metal-to-metal bond between said inner portion and said outer portion.

Description

ANODE HANGER (ANODE YOKE)

The present invention regards devices to conduct current to or from the electrodes of electrolysis cells for production of aluminium by electrolysis of alumina solved in a melted electrolyte.

Background.

Electrolysis is the chemical process which takes place at the electrodes when electric current is passed through an electrolyte in contact with electrodes. In the process, compounds which are dissociated into ions in the electrolyte is reduced at the cathode and oxidized at the anode, by means of the electric current. An important electrolysis processes is electrolysis of alumina solved in a melted halogenide electrolysis bath, for example an electrolysis bath of cryolite. The process often utilized when producing aluminium, is the Hall-Heroult-process, in which the electrolyte of the electrolysis bath is at a temperature up to 980 °C.

In the electrolysis of alumina for production of aluminium, energy losses due to reduced electrical current efficiency is a very significant part of the total cost, and a better electrical current efficiency would lead to significant savings.

The terms voltage drop, conductivity, resistance and current efficiency are used interchangeably in the following as it is found natural and are used in general by skilled persons, and the relationship between the terms, for example by the Ohm's law and Faraday's law for electrolysis are assumed well known to a person skilled in the art to which the present invention is related.

In cells for electrolysis of alumina for production of aluminium the anodes are usually formed of carbon with an inner current bus bar, namely anode hangers and anode bolt, whereto current is applied. The electrical current is passed from said current conducting devices through the carbon of the anode and into the electrolyte where electrolysis takes place, and further into the cathode, , and to the current conduction devices of the cathode.

A voltage drop appears all over the electrolysis cell, of which the most significant voltage drop appears over the electrolyte. However, voltage drop also appears over the current conducting devices comprising the anode hangers and the anode bolts, and current bus bars of the cathodes. The elctrical current through a typical electrolysis oven is typically in a range from 100000 ampere to 300000 ampere. Hence, only a small reduction of the voltage drop will significantly reduce electrical losses.

At present materials as iron or steel or iron- and steel alloys are used in the devices for conducting current, and some designs include outer or inner parts of copper or aluminium to minimize the voltage drop.

Electrical cathode bus bars are typically manufactured from massive steel, at least in the part which is to be incorporated into the cathode. Ends extending from the electrolysis cell could be of another material with a better electrical conductivity, such as for example copper. Also the part of the anode hanger or anode bolt for incorporation into the carbon is typically manufactured from steel. The upper, upwardly extending part via a bimetal transition is manufactured from aluminium. Several designs contain several welds, typically manual welds performed in difficult welding positions, with resulting poor quality with low conductivity and strength. The bimetal transition typically results in three welds represented by the manual welds above and below, and the high temperature and high pressure roll-welded bimetal welding.

In patent publication NO 162083 an anode hanger for holding a carbon containing anode in cells for production of aluminium has been described. The anode hanger disclosed in NO 162083 for use in Hall-Heroult-process cells for production of aluminium, includes an upper part of a metal such as aluminium, copper or steel, which is joined by an anode beam or something corresponding, and a lower current conducting steel part which is fastened to the upper part. The lower steel part comprises a yoke with downward extending nipples whereto the carbon containing anode is secured. The upper part is fastened to the lower steel part by means of a cast-joining of aluminium or copper. The yoke is according to NO 162083 produced by filling a void in the steel yoke by a melted suitable metal, with aluminium as the preferred metal for the application, which then solidifies and makes the inner part of the yoke.

In the aluminium production industry, the need for good heat and electrical conductors that are resistant towards corrosive environments dictates use of a metal of good conductivity, such as copper (Cu) and aluminium (Al). Cu is more expensive than Aluminium and the density is higher for Cu compared with Al. A reason for using Al, as disclosed in NO 162083, rather than copper, is less weight for the same conductance. Iron/steel are used in areas which are exposed for corrosion and high temperatures, this material(s) also have very good mechanical properties, however the electrical conductivity is relatively poor compared with Cu and AL.

Patent publication N0315090 to Servico AS, of 27.11.2000, and the corresponding publication WO/2002/042525, disclose an anode hanger comprising a steel outer portion covering a copper core portion, the copper core portion being a copper part shrink fitted to the the steel outer portion, or the steel outer portion being fitted over the copper core portion. According to the description in page 3, lines 2 - 35, the objective of the design disclosed in WO/2002/042525 is to provide improvements over the design disclosed in NO 162083, said to appear by experience not to be industrially applicable, one reason being the joining between the yoke components of cast metal and surrounding steel has not sufficient mechanical strength under the hars conditions to withstand thermal expansion, and that the components are disintegrated, in particular the joinings steel/aluminium.

Patent publication CN1626701 doscloses an anode hanger made from steel and having an internal space for accommodating an aluminium core.

It is an object of the invention to provide an anode hanger with improved performance, that solves problems of known anode hangers for reduced energy consumption, more cost effective manufacturing, reduced thermal and mechanical tress, reduced need for maintenance, overhaul and repair, lowered rate of failure, and an improved life cycle cost, thereby providing in most ways a more efficient process for production of metal by the electrolytic production process.

Summary of the invention.

The present invention provides an anode hanger according to the accompanying patent claim 1.

Further features of the anode hanger of the invention are recited in the accompanying dependent patent claims 2 - 15. In a first aspect, the an anode hanger according to the present invention, for an electrode of electrolysis cells for production of aluminium, comprises an inner portion of a copper material, and an outer portion of steel material. The outer portion is covering and bonded to a substantial part of said inner portion. Substantially all of an interface formed between said inner portion of a copper material and said outer portion of a steel material, where the outer portion is covering said substantial part of said inner portion, is provided by a bond at a molecular or atomic level between said copper material of said inner portion and said steel material of said outer portion.

According to a second aspect, in an advantageous embodiment of the anode hanger according to the first aspect above, said outer portion is covering at least 85% of an outer surface of said inner portion.

According to a third aspect, in a further advantageous embodiment of the anode hanger according to the first aspect above, said outer portion is covering at least 85% of an outer surface of said inner portion.

According to a fourth aspect, in a yet further advantageous embodiment of the anode hanger according to the first aspect above, said outer portion is covering at least 90% of an outer surface of said inner portion.

According to a fifth aspect, in a yet further advantageous embodiment of the anode hanger according to the first aspect above, said outer portion is covering at least 95% of an outer surface of said inner portion.

According to a sixth aspect, in an embodiment of the anode hanger according to any of the above aspects, at least 95% of said interface between said inner portion and said outer portion is providing a molecular or atomic level bond between said inner portion and said outer portion.

According to a sixth aspect, in an embodiment of the anode hanger according to any of the above first to fifth aspects, at least 98% of said interface between said inner portion and said outer portion is providing a molecular or atomic level bond between said inner portion and said outer portion. According to a seventh aspect, in an embodiment of the anode hanger according to any of the above first to fifth aspects, at least 99,5% of said interface between said inner portion and said outer portion is providing a molecular or atomic level bond between said inner portion and said outer portion.

According to an eigth aspect, in an embodiment of the anode hanger according to any of the above first to fifth aspects, at least 99,95% of said interface between said inner portion and said outer portion is providing a molecular or atomic level bond between said inner portion and said outer portion.

According to a nineth aspect, in an embodiment of the anode hanger according to any of the above aspects, the molecular or atomic level bond is substantially a metallic bond.

According to a tenth aspect, in an embodiment of the anode hanger according to the above nineth aspect, at least 95% of said molecular or atomic level bond is a metallic bond.

According to a eleventh aspect, in an embodiment of the anode hanger according to the above nineth aspect, at least 98% of said molecular or atomic level bond is a metallic bond.

According to a twelvth aspect, in an embodiment of the anode hanger according to the above nineth aspect, at least 99,5% of said molecular or atomic level bond is a metallic bond.

According to a thirteenth aspect, in an embodiment of the anode hanger according to the above nineth aspect, at least 99,95%> of said molecular or atomic level bond is a metallic bond.

In an embodiment of the anode hanger of the invention according to any of the above first to thirteenth aspects, the anode hanger comprises a yoke portion with a coupling portion for coupling the hanger to an electric feed bar, and a plurality of nipple portions, wherein an inner portion of copper material extending at least from the coupling portion and into each of said plurality of nipple portions provides a path of low electrical resistance and a continuous electrical connection to the surrounding steel material. In an embodiment of the anode hanger of the invention according to any of the above first to thirteenth aspects, the anode hanger comprises a yoke portion with a coupling portion for coupling the hanger to an electric feed bar, and a plurality of nipple portions, wherein the inner portion of copper material extends at least from the coupling portion and into each of said plurality of nipple portions, and ratio of an effective diameter of said inner protion and a thickness of said outer portion at a mid point between the coupling portion and any one of said plurality of nipple portions is at least %% .

In a first method for manufacturing the anode hanger of the present invention, the anode hanger is formed by pouring molten steel material at a high temperature into a properly shaped casting mould, inside which has been placed, before pouring of the molten steel, a premade body of a copper material. On bringing the molten steel into contact with the premade body of copper material, the copper material at the surface of the premade body reaches a temperature at which it mixes with or diffuses into adjacently located parts of molten steel material, and vice versa. The poured steel material and the copper body is then cooled down to normal temperatures in a controlled fashion. As the poured steel material and the copper body is cooled down and molten material solidifies, a solid metal-to-metal molecular or atomic level bond is formed at substantially all of the interface between the body of copper material and surrounding steel material that has been cast onto the copper body.

According to a fourteenth aspect, in an embodiment of the above first method for manufacturing the anode hanger of the present invention, the premade body of copper material is preheated and at an elevated temperature at the time when the molten steel material is poured into the casting mould.

According to a fifteenth aspect, in an embodiment of the above first method for manufacturing the anode hanger of the present invention, the premade body of copper material is kept at temperatures well below the melting point of the copper material at the time when the molten steel material is poured into the casting mould. After pouring of the molten steel material into the casting mould, heat is supplied to the casting mould and its content in order for a surface of the premade copper body that is in contact with the surrounding steel material to reach a temperature at which it reachs a soft or fluid state at which it is allowed to at least in part blend in with a surrounding steel fluid. When cooled to a temperature at which the copper solidifies, a strong metal-to-metal bond between the copper body and surrounding solidified steel material is formed over most of the surface of the copper body.

Detailed description.

In the following, the invention will be described by way of example and with reference to the accompanying drawings, in which

Figures 1 A, IB, 1C and ID are perspective view, perspective view including fantom lines showing hidden features, top view showing section plane, and side section view, respectively, drawings illustrating a first exemplary two nipple embodiment of an anode hanger according to the present invention; figures 2A, 2B, 2C and 2D are perspective view, perspective view including fantom lines showing hidden features, top view showing section plane, and side section view, respectively, drawings illustrating a second exemplary two nipple embodiment of an anode hanger according to the present invention; figures 3A, 3B, 3C and 3D are perspective view, perspective view including fantom lines showing hidden features, top view showing section plane, and side section view, respectively, drawings illustrating a first exemplary three nipple embodiment of an anode hanger according to the present invention; figures 4A, 4B, 4C and 4D are perspective view, perspective view including fantom lines showing hidden features, side section view, and top view showing section plane, respectively, drawings illustrating a first exemplary four nipple embodiment of an anode hanger according to the present invention; figures 5A, 5B, 5C and 5D are perspective view, perspective view including fantom lines showing hidden features, side section view, and top view showing section plane, respectively, drawings illustrating a first exemplary five nipple embodiment of an anode hanger according to the present invention; figures 6A, 6B, 6C and 6D are perspective view, perspective view including fantom lines showing hidden features, side section view, and top view showing section plane, respectively, drawings illustrating a first exemplary six nipple embodiment of an anode hanger according to the present invention; figure 6E is a perspective view drawing illustrating an inner part of copper material of the first exemplary six nipple embodiment of an anode hanger according to the present invention illustrated in figures figures 6A, 6B, 6C and 6D; figure 7 is a photography of a cross section of a nipple cut away from an anode hanger according to the present invention, illustrating the central location of the inner copper part, Cu, and the steel part, Fe, cast over and surrounding the inner copper part, and also the substantially uninterrupted Cu to Fe interface, I; figures 8A and 8B are partial photographies in a perspective view of a test block and in a side view of a specimen S cut from the test block, respectively; figure 9 is a graph showing a Fe-Cu phase diagram; figure 10 is a lk magnification SEM image showing on a microscopic scale of a representative part of an area comprising the interface I of the specimen S of figure 8B; figure 11 A is a SEM image in a slightly lower magnification than that of figure 10 of the representative part of the area comprising the interface I of the specimen S shown in figure 10; figures 1 IB, 11C , and 1 ID are graphs of chemical analysis linescans of 200um over the area comprising the interface I of figure 11 A showing the Wt% concentrations of Fe, Cu, and Si, respectively; figure 12A is a SEM image on a slightly higher magnification than that of figure 10 of the representative part of the area comprising the interface I of the specimen S shown in figure 10; figures 12B, 12C , 12D, and 12E are graphs of chemical analysis linescans of 50um over the area comprising the interface I of figure 12A showing the Wt% concentrations ofFe, Cu, Si, and Mn, respectively; figure 13 A is a SEM image of a representative part of the Fe material located adjacently to the area comprising the interface I of the specimen S shown in figure 10; figures 13B, 13C , 13D, and 13E are graphs of chemical analysis linsecans of lOOum over the area comprising the Fe material adjacent to the interface I of figure 13 A showing the Wt% concentrations of Fe, Cu, Si, and Mn, respectively; figures 14A and 14B are top view and side view photographies of a test block and a specimen S2 cut from the test block; figure 14C is a side view photographiy of the specimen S2 of figure 14B marked with a test location grid pattern and mounted in a second orientation in a test jig; figure 15A is a first graph illustrating recorded electrical test results with the specimen S2 mounted in a first orientation in the test jig, and figure 15B is a first graph illustrating recorded electrical test results with the specimen S2 mounted in the second orientation in the test jig.

In the following the anode hanger of the invention will be described and explained by way of example and with reference to the accompanying drawings in which the same reference numbers refere to the same or technically equivalent elements, and wherein the terms "inner portion of a copper material" and "copper core" are used

interchangeably, and the terms "outer portion of a steel material" and "steel lining" are used interchangeably.

Reference is first made to the drawings of figures 1 A, IB, 1C and ID, illustrating in two perspective views, in a top view, and in a side section view, respectively, a first exemplary two nipple embodiment of an anode hanger according to the present invention. The line B-B in figure 1C is to indicate the projection of the section plane for the cross section view of figure ID. This two nipple anode hanger embodiment comprises lower "nipple" parts 114, yoke "shoulders" 113, yoke "arms" 112, and yoke "head" 111. In figures 1A and IB is also shown an exposed upper area 121 of the head part of the Cu material inner portion of the yoke "head" 111, at which the anode hanger is connected electrically to a source of electric current for its use in the electrolytic process in metal production. In figure IB is also shown by fanthom lines geometriacal features of the hanger that are not visible in figure 1 A, such as the full contours of the lower faces of the head 11 and nipple 114 parts of the hanger, and the head part 121, arm parts 122, and shoulder parts 123 of the the Cu material inner portion of the yoke. In the cross section view of figure ID is more clearly illustrated a feature detail of this embodiment in which the copper body forming a core of the anode hanger extends from the exposed upper area 121 of the Cu material inner portion in the yoke "head" 111, to a part of the yoke at which the yoke "shoulder" 113 transits into the "nipple" 114.

Accordingly, in this embodiment of the anode hanger of the invention, the lower "nipple" part 114 does not include an inner portion of a copper material and constitutes a substantially all steel material part of the anode hanger. Although the head 111, shoulders 113, and nipple 114 parts of the anode hanger embodiment of these figures are of cylindrical shape with a substantially circular cross section, and the arms 112 are of cylindrical shape with a square or rectangular cross section, other shapes and cross sections geometries are contemplated, such as e.g. arms 113 that extends along a curved line, or wherein one or more of the aforementioned parts of the anode hanger have a non-uniform cross section over a respective length, such as e.g. a conical or an elliptic section.

For the following explanation of a second exemplary two nipple embodiment of an anode hanger according to the present invention, reference is made to the drawings of figures 2A, 2B, 2C and 2D, illustrating the second exemplary two nipple embodiment in two perspective views, in a top view, and in a side section view, respectively. The line B-B in figure 2C is to indicate the projection of the section plane for the cross section view of figure 2D. The overall shape and the main parts of the yoke of this exemplary two nipple embodiment of an anode hanger according to the present invention are substantially the same as those of the first embodiment explained above, however, a substantial difference lies in the shape of the copper core body which extends from the yoke shoulder 113 and into and through most of the nipples 114 by respective nipple part 124 extensions, so as to provide an inner portion of copper material that extends in continuity all the way from the yoke head 111 to that which in the figures 2A, 2B and 2C appear as the lower ends of the nipples 114. In figure 2B is also shown by fanthom lines geometrical features of the hanger that are not visible in figure 2A, such as the full contours of the lower faces of the head 111 and nipple 114 parts of the hanger, and of the head part 121, two arm parts 122, and two shoulder parts 123 of the the Cu material inner portion of the yoke, and of the two nipple parts 124 forming the Cu material inner portions of the nipples 114. As explained above for the first exemplary a two nipple embodiment, such other shapes and cross sections geometries are contemplated also for the second two nipple embodiment of the anode hanger. For the following explanation of a third exemplary three nipple embodiment of an anode hanger according to the present invention, reference is made to the drawings of figures 3 A, 3B, 3C and 3D, illustrating the third exemplary three nipple embodiment in two perspective views, in a top view, and in a side section view, respectively. The line C-C in figure 3C is to indicate the projection of the section plane for the cross section view of figure 3D. The overall shape and the main parts of the yoke of this exemplary three nipple embodiment of an anode hanger according to the present invention correspond to similar parts of the second embodiment explained above, however, a substantial difference lies in the addition of a third nipple 114 provided by an extension to the yoke immediately below the head 111 of the yoke. In figure 3B is also shown by fanthom lines geometrical features of the hanger that are not visible in figure 3 A, such as the full contours of the lower faces of the nipple 114 parts of the hanger, and of the head part 121, two arm parts 122, and two shoulder parts 123 of the the Cu material inner portion of the yoke, and of the three nipple parts 124 forming the Cu material inner portions of the nipples 114. As explained above for the other exemplary embodiments, such other shapes and cross sections geometries are contemplated also for corresponding parts of the three nipple embodiment of the anode hanger.

For the following explanation of a fourth exemplary four nipple embodiment of an anode hanger according to the present invention, reference is made to the drawings of figures 4A, 4B, 4C and 4D, illustrating the fourth exemplary four nipple embodiment in two perspective views, in a side section view and in a top view, respectively. The line D-D in figure ID is to indicate the projection of the section plane for the cross section view of figure 1C. The main parts of the yoke of this exemplary four nipple

embodiment of an anode hanger according to the present invention correspond to similar main parts of the first, second and third embodiments explained above, however, a substantial difference lies in the addition of a fourth nipple 114, and that the four nipples 114 are arranged in-line and symmetrically positioned with two nipples on each side of and spaced from the head 111 of the hanger. In figure 4B is also shown by fanthom lines geometrical features of the hanger that are not visible in figure 3 A, such as the full contours of the lower faces of each of the four nipples 114 of the hanger, and of the head part 121, two arm parts 122, and two shoulder parts 123 of the the Cu material inner portion of the yoke, and of the four nipple parts 124 forming the Cu material inner portions of respective ones of the four nipples 114. As explained above for the other exemplary embodiments, such other shapes and cross sections geometries are contemplated also for corresponding parts of the four nipple embodiment of the anode hanger.

For the following explanation of a fifth exemplary four nipple embodiment of an anode hanger according to the present invention, reference is made to the drawings of figures 5A, 5B, 5C and 5D, illustrating the fifth exemplary four nipple embodiment in two perspective views, in a side section view, and in a top view, respectively. The line M-M in figure 5D is to indicate the projection of the section plane for the cross section view of figure 5C. The main parts of the yoke of this exemplary four nipple embodiment of an anode hanger according to the present invention correspond to similar main parts of the first, second third, and fourth embodiments explained above, however, taking the first and second embodiments of two nipple embodiments as reference in which the two nipples 114 via respective arms 112 are attached to the head 111 at respective 0 and 180 degree positions of a circle about the head 111 with the head 111 at circle center, a substantial difference lies in that there are provided two additional nipples 114 and respective arms arranged in 90 and 270 degree positions of the circle, and the two additional nipples 114 attached to via said respective arms the head 111

correspondingly. In figure 5B is also shown by fanthom lines geometrical features of the hanger that are not visible in figure 5 A, such as the full contours of the lower faces of each of the four nipples 114 of the hanger, and of the head part 121, four arm parts 122, and four shoulder parts 123 of the the Cu material inner portion of the yoke, and of the four nipple parts 124 forming the Cu material inner portions of respective ones of the four nipples 114. As explained above for the other exemplary embodiments, such other shapes and cross sections geometries are contemplated also for corresponding parts of the fifth exemplary four nipple embodiment of the anode hanger.

For the following explanation of a sixth exemplary six nipple embodiment of an anode hanger according to the present invention, reference is made to the drawings of figures 6A, 6B, 6C and 6D, illustrating the fifth exemplary four nipple embodiment in two perspective views, in a side section view, and in a top view, respectively. The line F-F in figure 6D is to indicate the projection of the section plane for the cross section view of figure 6C. The main parts of the yoke of this exemplary six nipple embodiment of an anode hanger according to the present invention correspond to similar main parts of the first, second third, fourth, and fifth embodiments explained above, however, taking the fifth exemplary embodiment of a four nipple anode hanger as reference in which the four nipples 114 via respective arms 112 are attached to the head 111 at respective 0, 90, 180, and 270 degree positions of a circle about the head 111 with the head 111 at circle center, a substantial difference lies in that the arms 112 at 90 and 270 degree positions are extended and split into two branches each carrying a respective one of four nipples, bringing the total of nipples 114 to six, with three of the six nipples arranged in-line with each other on each of two parallel lines spaced from and at respective sides of the head 111. In figure 6B is also shown by fanthom lines some of the geometrical features of the hanger that are not visible in figure 6A, such as the full contours of the head part 121, six arm parts 122, and six shoulder parts 123 of the the Cu material inner portion of the yoke, and of the six nipple parts 124 forming the Cu material inner portions of respective ones of the six nipples 114. As explained above for the other exemplary embodiments, such other shapes and cross sections geometries are contemplated also for corresponding parts of the sixth exemplary four nipple embodiment of the anode hanger.

For the following explanation made by way of example of the copper body provided for the Cu inner portion of an anode hanger according to the invention, reference is made to the drawing of figures 6E illustrating in a perspective view a copper body for the exemplary six nipple anode hanger embodiment. The main parts of the copper body for the exemplary six nipple embodiment of an anode hanger according to the present invention correspond to similar main parts of copper bodies for the first, second third, fourth, and fifth anode hanger embodiments explained above, and comprises at least a head part 121, a plurality of arm parts 122, and a plurality of shoulder parts 123, and optionally also one or more nipple parts 124. Referring again also to the explanation above of the first exemplary embodiment of a two nipple anode hanger, a copper body for the first embodiment does not include nipple parts 124 shown and explained for other embodiments. Accordingly, by optionally including or not including the nipple parts 124 of the copper body, corresponding varieties of the anode hanger of the invention can easily be provided with or without Cu material inner portions in nipples 114. Furthermore, it is contemplated that for anode hangers according to the invention in which the paths along the Cu material inner protion from the head 111 to the nipples 114, along respective arms 112, are not identical in shape or length, the cross section area of parts of the copper body is varied to minimize differences in the voltage drop between the head 111 and the nipples 114. Taking as an example the copper body of figures 6E provided for the Cu inner portion of the exemplary six nipple embodiment anode hanger according to the invention, in which there are four arm parts 122 extending outwards from the head, the portions of two arm parts 122 that are extending from the head part 121 towards respective branching points are provided with a larger cross section area than the portions of the other two arm parts 122 that are extending from the head part 121 to the shoulder parts 123 without branching. It is also contemplated to provide the the portions of four arm parts 122 that are extending from the respective branching points to respective ones of four shoulder parts 123 with a correspondingly larger cross section area, also to provide an electrically better conducting path for current to flow and result in voltage drops between the head 111 and any of the nipples that are substantially the same when the anode hanger is in operation in an electrolysis cell for production of metal or the like.

For the following explanation of details of characteristics of a metal-to-metal bond and typical geometries of a coper core and surrounding steel material of an anode hanger according to the invention, reference is made to figure 7, illustrating in a photography a typical appearance of a cross section of a structure corresponding to that of a nipple, as seen at a point at which it has been cut away from an anode hanger according to the present invention. A clearly visible central area marked Cu, is the inner copper part, showing as a feature of somewhat darker color than the immediately surrounding material of steel material, marked Fe, which has been cast over and is entirely surrounding the inner copper part. The area of the copper core being in contact with the surrounding steel material exhibits an irregular, but substantially uninterrupted Cu to Fe interface, marked I. In the illustrating example of figure 7, part of the copper core that in motlen state has entered a state of relatively low viscosity has flowed to form a clearly visible protuberance into the surrounding steel material, forming a further good electrical and mechanical coupling between the Cu inner portion and the surrounding Fe outer portion.

For the following explanation of details of characteristics of a metal-to-metal bond and typical geometries of a copper core and surrounding steel material of corresponding to that of an anode hanger according to the invention, reference is made to figures 8 A and 8B, illustrating in respective photographies a copper rod Cu cast into and surrounded by a steel material ingot Fe and from which a specimen volume S has been cut away, and of the specimen, respectively. The specimen length is about 100mm long and width is about 20mm. In figure 8A an arrow is pointing to the surface of the specimen that after cutting and polishing has the appearance of the specimen illustrated in the photography of figure 8B. In both figures 8 A and 8B, the bond or interface between the copper material portion and the steel material portion is marked I. A typical characteristic of the bond or interface I is that it runs in continuity without indications of any substantial separation or gap, and that a metal-to-metal bond has been formed between the copper materal portion and the surrounding steel material portion. Also shown in figure 8B is an area C showing a void in the copper material portion, attributed to a presence of an oxide or other constituent of the copper material that would produce a gas bubble when the copper material is heated sufficiently to become a fluid. Other features that differentiate from each other the areas marked A and B of the copper material portion located away from the steel material portion surrounding the copper material portion, are the observed plurality of smaller particles or inclusions of the Fe material randomly distributed in the area marked B that are not present in the area marked A.

For the following further explanation of details of characteristics of a metal-to-metal bond and typical geometries of an interface between a copper core and surrounding steel, and of material located adjacently to the interface are I, corresponding to that of an anode hanger according to the invention, reference is made to figure 10. In figure 10 is illustrated in a photography a lk magnification scanning electron microscope, SEM, image showing on a microscopic scale of a representative part of an area comprising the interface I between the copper material portion and the steel material portion of the specimen S also illustrated in full scale in figure 8B. Also on a microspocic scale is clearly shown the typical characteristic of the metal-to-metal bond or interface I that runs in continuity without indications of any substantial separation or gap, thereby providing an excellent electrical and mechanical coupling between the copper material portion and the steel material portion.

For the following further explanation of details of characteristics of a metal-to-metal bond, of typical geometries of an interface between a copper core and surrounding steel, and of material located adjacently to the interface are I, typical to that of an anode hanger according to the invention, reference is made to figures 11 A- 1 ID. In figure 11 A is shown an SEM image, in a slightly lower magnification than that of figure 10, of the representative part of the area comprising the interface I of the specimen S shown in figure 10, including a substantially horizontal line of length 200um positioned almost symmetricaly with respect to the metal-to- metal bond or interface I, along which a chemical analysis line scan has been made. The results of the chemical analysis line scan has been illustrated in figures 1 lB-1 ID, from which it is seen that in an anode hanger according to the invention, a plurality of smaller steel material inclusions or precipitation could be observed in the copper material portion at a significant distance from the the metal-to- metal bond or interface I, and that in a cross section the metal-to- metal bond or interface I itself exhibits a clearly defined and continuous but somewhat irregular pattern, and that there is a noticeable trace of copper material in the steel material portion to a depth of about 20um from the clearly defined interface I.

For the following further explanation of details of characteristics of a metal-to-metal bond, of typical geometries of an interface between a copper core and surrounding steel, and of material located adjacently to the interface are I, typical to that of an anode hanger according to the invention, reference is made to figures 12A-12E. In figure 12A is shown a further SEM image, in a slightly higher magnification than that of figure 10 (about four times that of figure 11), of a part of the representative part of the area comprising the interface I of the specimen S shown in figure 10, including a

substantially horizontal line of length 50um positioned almost symmetricaly with respect to the metal-to- metal bond or interface I, along which a chemical analysis line scan has been made. The results of the detailed chemical analysis line scan over 50um across the the metal-to- metal bond or interface I has been illustrated in figures 12B- 12E, from which it is seen that in an anode hanger according to the invention steel material inclusion or precipitation could be observed as relatively thinly spread out in the copper material close to the metal-to- metal bond or interface I, and that in a cross section the metal-to- metal bond or interface I itself also at this higher magnification exhibits a clearly defined and continuous but somewhat irregular pattern, and that the observation from figures 11 A-l ID of a noticeable trace of copper material in the steel material portion to a depth of about 20um from the clearly defined interface I is confirmed.

For the following further explanation of details of characteristics of a metal-to-metal bond, of typical geometries of an interface between a copper core and surrounding steel, and of material located adjacently to the interface are I, typical to that of an anode hanger according to the invention, reference is made to figures 13A-13E. In figure 13 A is shown a further SEM image, in a slightly higher magnification than that of figure 10 (about two times that of figure 11), of a part of the representative part of the area comprising the interface I of the specimen S shown in figure 10, including a

substantially horizontal line extending from the metal-to- metal bond or interface I and lOOum into the steel material portion, along which a chemical analysis line scan has been made. The results of the detailed chemical analysis line scan over lOOum from the metal-to- metal bond or interface I has been illustrated in figures 13B-13E, from which it is seen that in an anode hanger according to the invention there is a noticeable depletion of Si and Mn from the steel material portion to about 25um from the metal-to- metal bond or interface I, and that in a cross section the metal-to- metal bond or interface I itself also at this higher magnification exhibits a clearly defined and continuous but somewhat irregular pattern, and that the observation from other chemical analysis linescans of a noticeable trace of copper material in the steel material portion to a depth of about 20um from the clearly defined interface I is confirmed.

For the following explanation of further details of characteristics of a metal-to-metal bond and of typical geometries of an inner copper portion and surrounding steel material corresponding to that of an anode hanger according to the invention, reference is made to figures 14 A, 14B, and 14C, illustrating in respective photographies an image of ingot comprising a copper rod Cu cast into and surrounded by a steel material Fe with a specimen volume S2 cut loose from the ingot, an image of a polished test surface of the specimen S2, and an image of the specimen S2 marked with a test reference pattern and mounted in a test jig, respectively. In figure 14A an arrow is pointing to the surface of the specimen S2 that after cutting and polishing has the appearance of the specimen S2 illustrated by the images of the photographies of figures 14B and 14C. In both figures 14 A, 14B and 14C, the bond or interface between the copper material portion and the steel material portion is marked I, and the copper material and steel material portions Cu and Fe, respectively, are clearly visible by differences in appearance by color. Similar to what has been observed for the specimen S imaged in figures 8B, the typical characteristic of the bond or interface I being that it runs in continuity without indications of any substantial separation or gap, and that a metal-to- metal bond has been formed between the copper materal portion and the surrounding steel material portion, can be observed also from the images of figures 14B and 14C. Figure 14C is an image of the specimen S2 mounted in a second orientation in an electrical test jig, with copper slabs Ell and E12 constitute first and second electrodes that form electrical contacts to oppositely located sides of the specimen S2 for performing electrical testing. With the specimen S2 in the second orientation in the test jig, the slab Ell connects exclusively to the steel material portion furthest away from the interface I, while the slab E12 connects exclusively to the copper material portion furthest away from the interface I, as shown in figure 14C. In the tests, an electric current of 100 A is passed through the specimen S2 from electrode Ell to electrode E12, and a voltage drop in the specimen S2 over a distance equal to the width of one cell of the eight by ten column/row cell grid marked A-H/l-9 is measured on the surface of the cells, along a row or a column, depending on the orientation of the specimen S2 in the test jig. With the specimen S2 positioned in the jig in the second orientation, as illustrated in figure 14C, ten measurements are performed in a first test along each of the columns A-H, the results of which are shown in the line graphs of figure 15B. In a second test with the specimen S2 in the test jig in a first orientation in which it has been rotated 90 degrees from the orientation shown in figure 14C, in which both slabs Ell and EL2 connect to both the steel protion and the copper portion at respective opposite sides of the speciemnt S2, eight measurements are performed along each of the lines 4 and 5 that are located adjacently to and on respective copper and steel material sides of the interface I, the results of which are shown in figure 15 A, in which the lower line graph represents values measured on the line with label 4 in the copper material portion, and the upper line graph represents values measured on the line with label 5 in the steel material portion.

Advantages.

It is estimated that the electrical resistance of the anode hanger according to the invention could be up to 30% lower than the electrical resistance of other comparable anode hangers. Consequently, the electrical power dissipated in the anode hanger is reduced accordingly, having the effects of extending the lifetinme of the anode hanger, reducing cost and resources used for maintaining and replacing anode hangers in a facility for electrolytic cell metal production, and a favorable overall reduction in energy consumption in the process that makes use of the anode hanger. A further effect of the technology of the present invention is increased pot efficiency and a the refractory considerably better lining lifetime. This is mentioned as a reference to our invention and the fact that if the theoretical analysis is correct the distribution of the current can be equally distributed through the cell through the design of the cupper insert in the anode, which will provide an even longer lifetime to the refractory lining

Claims

P a t e n t c l a i m s 1.

An anode hanger for an electrode of electrolysis cells for production of aluminium, comprising

an inner portion of copper material having a first surface and an outer portion of steel material covering and bonded to a substantial part of said first surface of the inner portion,

wherein an interface between said inner portion and said outer portion provides a substantially continuous metal-to-metal bond between said inner portion and said outer portion.

2.

The anode hanger of claim 1, wherein said outer portion is covering at least 85% of an outer surface of said inner portion.

3.

The anode hanger of claim 1, wherein said outer portion is covering at least 90% of an outer surface of said inner portion.

4.

The anode hanger of claim 1, wherein said outer portion is covering at least 95% of an outer surface of said inner portion.

5.

The anode hanger of any one of claims 1, 2, 3 and 4, wherein at least 95% of said interface between said inner portion and said outer portion is providing a metal-to- metal bond between said inner portion and said outer portion.

6.

The anode hanger of any one of claims 1, 2, 3 and 4, wherein at least 98% of said interface between said inner portion and said outer portion is providing a metal-to- metal bond between said inner portion and said outer portion.

7.

The anode hanger of any one of claims 1, 2, 3 and 4, wherein at least 99,5% of said interface between said inner portion and said outer portion is providing a metal-to- metal bond between said inner portion and said outer portion.

8.

The anode hanger of any one of claims 1, 2, 3 and 4, wherein at least 99,95% of said interface between said inner portion and said outer portion is providing a metal-to- metal bond between said inner portion and said outer portion.

9.

The anode hanger of any one of previous claims, wherein the metal-to-metal bond is substantially a metallic bond.

10.

The anode hanger of claim 9, wherein at least 95% of said metal-to-metal bond is a metallic bond.

11.

The anode hanger of claim 9, wherein at least 98% of said metal-to-metal bond is a metallic bond.

12.

The anode hanger of claim 9, wherein at least 99,5% of said metal-to-metal bond is a metallic bond.

13.

The anode hanger of claim 9, wherein at least 99,95% of said metal-to-metal bond is a metallic bond.

14.

The anode hanger of any one of the previous claims, wherein the steel material includes about 0,4Wt% of Si.

15.

The anode hanger of any one of the previous claims, wherein the steel material includes about l,6Wt% of Mn.