FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
(As Amended by Patents Amendment Rules-2006)
COMPLETESPECIFICATION (See Section 10 and Rule 13)
TITLE OF THE INVENTION
A system and method for production of anode stem by extrusion process
APPLICANT
Hindalco Industries Limited, an Indian company and having address as Aditya Birla Centre,
S K Ahire Marg, Worli, Mumbai- 400030, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes this invention and the manner in which it is to be performed

TECHNICAL FIELD OF THE INVENTION
[001] The present invention in general relates to a field of metal forming
technology. More particularly, the invention relates to the production of anode stems by extrusion process.
DESCRIPTION OF THE PRIOR ART
[002] An anode stem plays a major role in the extractive metallurgy to extract base
metals like silver, copper, aluminium and others from the ore in the smelters. The anode stem is a metallic part usually formed in rectangular shape and is used in anode assembly mainly for carrying current and supporting an anode. The materialistic property of the anode stem should be such that the anode stem should have a high conductivity along with enough strength and hardness to support the anode below the anode stem.
[003] Currently the anode stem is produced by casting process as the casting
process the enables production at large scale. The anode stem is preferably casted by direct chill casting method. Though casting is suitable for large scale production, it has many disadvantages especially if the anode stem is produced using direct chill casting. For example, in the direct chill casting, thermal contraction occurs because of different thermal history of various sections of the anode stem and the various sections contract at different times and at different rates. This differential in contraction produces stress, as one section restrains another. The level of the stress in an inherent aspect of the direct chill casting process. Inability to acknowledge and control the stress produced during casting will inevitably lead to scrap and hazardous situations.
[004] Once a section has solidified and contracted, the section resists further
contraction. Consequently, when adjacent sections solidify and attempt to shrink stress is usually produced. Similarly, the shrinkage of the solid will not be uniform but will be determined by the thermal gradients present. It is this difference that gives rise to the variation in shape of the roll face of the anode stem produced using direct chill casting.
[005] The problem of thermal contraction may further be observed in cases where
the anode stem comprises circular sections. With the circular sections, in the mould,

metal first solidifies as a ring or annulus of solid forms. Each circular section is cooled by the water spray and thermal contraction takes place. As the casting continues, the metal in the centre will freeze and its natural tendency would be to shrink. However, at this stage the surface material is almost at the water temperature and has no tendency to contract. This may lead the outer section to have compressive stress and the inner section to have tensile stress.
[006] Casting process has also a disadvantage of tooling cost, as large number of
tools are required for different types of casting. Further, the anode stem produced by casting is also prone to shrinkage defects and shrinkage porosity. These defects are formed when the molten metal is poured and chilled directly by water. The metal starts to shrink at mushy zone and solidifies quickly by forming hollow air pipes and caved surfaces to compensate the shrinkage volume. These shrinkage defects are formed due to hotspots in the metal and other impurities in metal which have different cooling rates. These defects may lower the internal soundness, smoothness and surface finish of the anode stems.
[007] Gas porosity is another defect which may lower the internal soundness of the
casted product. It occurs because molten metal has the capability of holding large amount of dissolved gases and the molten metal may lose this capability when the molten metal solidifies leaving gas bubble inside the solid structure.
[008] In addition to defects, certain properties like hardness and electrical
conductivity are also hampered due to the defects formed in casting. The defects occurring in the casting process are unavoidable and can be reduced only to a certain extent. Casting process requires close process control and monitoring.
SUMMARY OF THE INVENTION
[009] In an aspect of the present invention, a method of producing an anode stem is
described that may comprise casting a uniformly grained aluminium material. The method may further comprise extruding the uniformly grained aluminium material through a feeder die and a bolster to obtain an extruded aluminium material with

required profile and length. The method may further comprise traversing the extruded aluminium material towards a hot saw cutter via one or more rollers and a puller. The method may further comprise cutting the extruded aluminium material, using the hot saw cutter into one or more aluminium pieces of equal length, wherein an aluminium piece of the one or more aluminium pieces indicates an anode stem to be used for supporting an anode in a smelting process.
[0010] In some embodiments, the method of producing an anode stem further includes cooling the anode stem using a quenching means, fabricating the anode stem using a fabricating means, and straightening the anode stem using a pressing means.
[0011] In another aspect of the present invention, a system for producing an anode stem is described that may comprise a casting means for casting a uniformly grained aluminium material. The system may further comprise extruding means for extruding the uniformly grained aluminium material through a feeder die and a bolster to obtain an extruded aluminium material with required profile and length. The system may further comprise traversing means for traversing the extruded aluminium material towards a hot saw cutter via one or more rollers and a puller. The system may further comprise cutter to cut the extruded aluminium material, using the hot saw cutter, into one or more aluminium pieces of equal length are disclosed, wherein an aluminium piece of the one or more aluminium pieces indicates an anode stem to be used for supporting an anode in a smelting process.
[0012] In some embodiments, the uniformly grained aluminium material is casted by hot top casting by establishing airflow levels in moulds to develop an air-slip in order to cool the aluminium material and to obtain uniformly grained surface finish on the casted aluminium material.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The detailed description is described with reference to the accompanying Figures. In the Figures, the left-most digit(s) of a reference number identifies the Figure in

which the reference number first appears. The same numbers are used throughout the drawings to refer like features and components.
[0014] Figure 1 illustrates a system architecture for producing the anode stem from raw aluminium material, according to an embodiment of the present invention;
[0015] Figure 2 illustrates an assembly line from the extrusion of the uniformly grained aluminium material to the cutting of the extruded aluminium material, according to another embodiment of the present invention; and
[0016] Figure 3 illustrates a method of producing the aluminium anode stem of FIG.l according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
[0017] The present invention in general relates to a metal forming process, such as aluminium or aluminium alloys. More particularly, the invention relates to a method of production of aluminium anode stem using an extrusion process and the arrangements in the machineries and process to overcome the limitations occurring in producing the anode stem by extrusion process.
[0018] Anode stems (hereinafter also referred aluminium anode stems) are longitudinal metallic elements used in metal extracting smelters. The anode stems are used mainly for carrying current and supporting an anode. The anode may be a carbon anode or a graphite anode. The physical and chemical properties of the anode stem are such that the anode stem should have enough strength and hardness to support the anode below them and should have least electrical resistance to carry large amount of current.
[0019] For the purpose of this invention 'smelting' is a form of extractive metallurgy. The main use of smelting is to produce a base metal from its ore. Base metal includes production of silver, iron, copper and other base metals from base metal ores. The Smelting process make use of heat and a chemical reducing agent to decompose the ore,

driving off other elements as gases or slag and leaving just the metal base behind. The reducing agent is commonly a source of carbon such as graphite, coke, or in earlier times charcoal. The carbon (or carbon monoxide derived from it) removes oxygen from the ore, leaving behind the elemental metal. The carbon is thus oxidized in two stages, producing first carbon monoxide and then carbon dioxide. The plant in which smelting is executed is known as smelter.
[0020] The extrusion produces compressive and shear forces in the stock. No tensile stress is produced, which makes high deformation possible, without tearing the metal. The cavity in which the raw material is contained is lined with a wear resistant material. This can withstand the high radial loads that are created when the material is pushed by the die. Extrusions often minimize the need for secondary machining.
[0021] Referring to Figure 1, an architecture of the system is represented along with its components for producing the aluminium anode stems by extrusion process. The system comprises a casting means (101), an extruding means (102), a traversing means (103), a hot saw cutter (104) (hereinafter also referred as cutting means), material handling means (105), quenching means (106), a fabricating means (107), a pressing means (108) and other auxiliary equipment (not shown). It is to be noted that the present embodiment describes invention for aluminium anode stem, however this system and method may be applied over a range of composition of aluminium alloys and other metals capable of extrusion.
[0022] In an embodiment, the casting means (101) is required for producing a semifinished uniformly grained aluminium casting material or a billet (hereinafter also referred as billet aluminium) which may be further used for extrusion. The billet is one of the four types of raw materials or semi-finished products. The other three raw materials or semi-finished products include ingots, blooms and slabs. The billets have the advantages comprising cost effectiveness in low quantities, high degree of precision, very short lead times, structurally the parts are stronger. The billet aluminium is formed in a completely different manner. It must be noted that the billet (or the billet aluminium) is a length of metal that has a round or square cross-section. The billet may be created

directly via hot top casting, continuous casting or extrusion or indirectly via hot rolling an ingot or bloom. While casting the billets by hot top casting, an airflow level may be established in individual moulds to develop air-slip. The Air slip may provide most of the cooling through direct water quench, resulting in a shallow sump and a very thin-shelled, uniform-grained billet with excellent surface smoothness. The size of the billet ranges from 13 inch to 14-inch diameter. Due to a large size casting, higher metal flow rate occurred which further resulted in risk of bleed out. Therefore, to avoid the bleed out in the billet, immediate plugging of mould was executed by plugging materials comprising fibreglass, wax, UV cure polyester resin, gloss resin.
[0023] In an embodiment, extruding means (102) further comprises a hot extrusion chamber, an extrusion press, a ram, a feeder die (hereinafter also referred as die), a bolster, and a bearing. The billet may form here as the blank or the material for extrusion. The extrusion is executed by placing the billet in a heavy walled container. The billet is pushed through the die by the ram. There is a reusable dummy block between the ram and the billet to keep them separated. The design of an extrusion profile has a large impact on how readily billet can be extruded. The maximum size for the extrusion is determined by finding the smallest circle that will fit around the cross-section, this is called the circumscribing circle. This diameter, in turn, controls the size of the die required, which ultimately determines if the part will fit in a given press.
[0024] In an exemplary embodiment, the circumscribing diameter here will be of 301±2 mm to produce an extruded anode stem of 220 x 220 mm with a tolerance of ±4 mm. The feeder die is designed such that along with the required profile, an extrusion length limit of about 2.47 to 2.51 meter with the upper and lower tolerance limits respectively is desired. The bearing for the extrusion die was blended by computer numeric controlled machine to meet the required level of fitting. The bolster provide support for the die during the extrusion process and contribute to improved tolerance controls and extrusion speeds.
[0025] In an embodiment, traversing means (103) comprise the equipment used after immediate extrusion of billets. The traversing means may be rollers for sliding the

extruded stem forward, pullers to hold and pull the extruded material and send the extruded material to the hot saw cutter (104). Due to the large size of the extruded material, a provision may be needed to support one or more rollers for bearing the load of the extruded material. The rollers are generally supported by pneumatic actuators which make the rollers to stand still by absorbing the load of the extruded material. Due to heavy load of the extruded aluminium material, the height of the rollers may be lowered and therefore the extruded aluminium material may not proceed directly in the hot saw opening and may hit in the area below the opening. In order to raise the rollers permanently, one or more brackets (208) are designed and installed below the rollers in order to withstand the weight of the anode stems by the rollers. To synchronise in height with the permanently raised rollers, the puller is raised to the required height. The hot saw cutter (104) is used to cut the hot extruded aluminium material smoothly. The hot saw cutter (104) may be made up of cemented carbide steel, high speed and high temperature tool steel. In order to avoid jamming of the hot saw blade in the extruded section, the speed of the cutter (104) may be reduced to obtain high torque in blade to overcome the jamming force.
[0026] In an embodiment, the material handling means (105) comprises overhead crane, wooden fixture, billet tongs, pressure tongs, gripping tongs and the like. The material handling means (105) are capable of handling the anode stem in the range of 120 - 140 kg/meter with the help of overhead cranes and tongs. Provision of holding the anode stems while machining is enabled by the overhead cranes.
[0027] In an embodiment, quenching (106) means further comprise a quenching box, a quenching medium (also referred as a quenchant) and other miscellaneous devices. The quenching box may be a container filled with the quenching medium comprising, brine, oil or water to increase the severity of the quenching. The objective of the quenching is to ensure that the dissolved constituents remain in solution down to room temperature. The quenching box is so designed to meet the work load and the ability of the quenchant to extract the heat at sufficient rate to achieve the desired results. The anode stem after extrusion are quenched to ambient temperature for facilitating its handling at down line.

[0028] In an embodiment, the fabricating means (107) further comprise a horizontal boring machine, a drilling machine, and a vertical press machine. Chamfering of the anode stem may be performed on the boring machine. A hole of 63 ± 5 mm may be drilled using the drilling machine. Further, a sleeve may be machined on a lathe machine and the sleeve is pressed in the hole by the vertical press machine.
[0029] In one embodiment, the vertical press machine may also be used for straightening of the anode stem. It is to be noted that the straightening after extrusion is required on regular basis, however, by stabilizing the manufacturing process, need for straightening of anode stems may be reduced with time.
[0030] Referring figure 2, an assembly line comprising the extruding means 102, the traversing means (103) and the hot saw cutter (104) is illustrated. The extruding means (102) comprises the ram (201) for pressing the billet aluminium material (202) which is casted in the form of one or more billets.
[0031] In an embodiment, a billet aluminium material (202) may be used in the blank
chamber (203) for each extrusion process. The ram (201) forces the uniformly grained billet aluminium material (202) to deform and shear through a die (204) and a bolster (205) to produce an extruded aluminium material (206).
[0032] In an implementation, the extruded aluminium material (206) may be traversed through the traversing means (103) comprising one or more rollers (207) and a puller (209). The one or more rollers (207) may be raised permanently to bear the heavy load of the extruded aluminium material (206) and to traverse the extruded aluminium material (206) to the hot saw cutter (104). The raising of the one or more rollers (207) may be enabled by fabricating and attaching a bracket (208) below each roller (207). In order to synchronise with the height of the rollers (207) raised, the height of the puller (209) may be raised relative to puller's traversing track to form a parallel traversing of the extruded aluminium material (206) with ground.

[0033] In another implementation, an opening (210) of the hot saw cutter (104) may be enlarged or increase to accommodate the safe input of the extruded aluminium material (206) in the hot saw cutter. The hot saw cutter (104) may be a circular cutter capable of cutting by continuous rotation. The hot saw cutter may be made up of high speed tool cutting steel, carbide cemented material and the like. Extruded aluminium material (206) of equal length may be cut by the hot saw cutter (104) to produce one or more pieces of aluminium material wherein an aluminium piece from one or more aluminium pieces indicates the anode stem.
[0034] Referring Figure 3, a method is represented to execute the one or more processes required to produce the finished aluminium anode stem from the aluminium raw material. At step 301, the aluminium alloy material is casted from the aluminium alloy's parent material which is mainly aluminium along with alloying elements. The aluminium material is casted by hot top casting method by developing air flow levels in the mould to obtain an air-slip for cooling purpose. The air slip may obtain uniformly grained aluminium billets (202).
[0035] The uniformly grained aluminium billet (202) is used as a blank material for extrusion of the aluminium material. At step 302, before proceeding for the extrusion of the uniformly grained aluminium material (202) certain provisions are made for the traversing means (103) of the extrusion comprising rollers (207), pullers (209) and hot saw cutter (104) along with its opening (210). The rollers (207) carry the weight of the extruded aluminium material (206) by the help of pneumatic actuators which absorb the weight of the extruded aluminium material and maintain the same level of height. But due the large weight of the extruded material ranging (206) from 120 k/m to 140 kg/m the pneumatic actuators may not bear the load and may suppress the height level resulting the lead of extruded aluminium material to go in a non-routed direction. To overcome lowering of the height of the roller (207), a provision is made for the roller (207) with bracket (208) designed to overcome the heavy weight and to raise the rollers (207) permanently. To synchronise the height for the permanently raised rollers (207), the height of the pullers (209) is also raised to the level of the rollers (207). This change in

downline equipment may help in the traversing of the extruded aluminium material towards the opening (210) of the hot saw cutter (104). The opening (210) of the hot saw cutter (104) is increased so as to accommodate the profile of the extruded material. To avoid jamming of the hot saw cutter (104) while cutting the extruded aluminium material, the cutter speed is decreased in order to get an increased torque in the cutter wheel which enables the teeth of the cutter to cut smoothly with greater force.
[0036] At step 303, a feeder die (204) arrangement along with the bolster (205) is designed and implemented to obtain the required square profile of side 220 ± 4 mm with a circumscribing circle diameter of 301 mm ± 2mm. The use of the bolster (205) along with the feeder die (204) is designed so as to improve the extrusion finish and the speed of extrusion. The assembly of the feeder die (204) may extrude a length of 2.47 to 2.51 metre of extruded aluminium by its lower and upper dimensions respectively. For fitting the bearing of the feeder the die (204), the bearing is blended on computer numeric controlled machines to obtain optimum level of precision.
[0037] At step 304, after complete set up of the extruding means (102), the casted uniformly grained billet aluminium material (202) is extruded to form extruded aluminium bars (206) or material and cut into one or more aluminium pieces to form one or more aluminium stems. The length of the aluminium stem may range between 2000 ± 50 mm.
[0038] At step, 305 the freshly cut one or more hot aluminium anode stems are uniformly cooled by quenching in a suitable quenching box containing quenching media comprising brine, water or oil. In an embodiment, the quenching may also be enabled by quenching medium comprising air, nitrogen etc.
[0039] At step, 306 each anode stem is further fabricated by machining operations to enable the anode stem for its end use. The anode stem being hold by the overhead crane is chamfered at anode stem's end by horizontal boring machine. Furthermore, the anode stem is drilled at its end on drilling machine with 60-65 mm diameter hole. A sleeve of suitable material and dimension is machined on the lathe machine to fit it in the drilled

hole. The sleeves were press fitted in the drilled hole via a press machines and then flared at its offset.
[0040] At step, 307 each anode stem is straightened by pressing bent anode stem by the pressing machine. To avoid dents and scratches on the lower side of anode stem, jute bags were inserted. Set the anode stem bent on a punch and press the anode bent portion below the punch. This process is iterative by checking the straightness with the help of straight edge. Anode stem bending may also be executed on used anode stem and hence it may be repetitive process.
[0041] At step, 308 each anode stem is tested ultrasonically to check internal soundness and optically to check the microstructure.
[0042] By producing the anode stem by extrusion process over casting process an increase in electrical conductivity with 51.5 IACS as compared with 40.61 IACS in casting process. Lower hardness (RH 68 - RH 70) obtained by extruded method of the stems leads to better grip with the bus bar thereby ensuring smooth & trouble free operation. Internal soundness of the extruded stem was found better as compared to casted. Non porous structure in the extruded enable better micro-structure.
[0043] The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

We Claim:
1. A method of producing an anode stem, the method comprising:
casting a uniformly grained aluminium material (202); extruding a uniformly grained aluminium material through a feeder die (204) and a bolster (205) to obtain an extruded aluminium material (206) with required profile and length;
traversing the extruded aluminium material (206) towards a hot saw cutter (104) via one or more rollers (207) and one or more pullers (209); and
cutting the extruded aluminium material, using the hot saw cutter (104), into one or more aluminium pieces of equal length,
wherein an aluminium piece of the one or more aluminium pieces indicates an anode stem to be used for supporting an anode in a smelting process.
2. The method as claimed in claim 1, further comprising
cooling the anode stem using a quenching means (106); fabricating the anode stem using a fabricating means (107); and straightening the anode stem using a pressing means (108).
3. The method as claimed in claim 1, further including providing a fabricating bracket (208) for raising position of the one or more rollers (207) and fetching the weight of the extruded aluminium material (206).
4. The method as claimed in claim 3, wherein the one or more pullers (209) are raised relative to track of the one or more pullers in order to match with the one or more rollers (207) raised.
5. The method as claimed in claim 1, wherein the opening (210) of the hot saw cutter (104) is increased to accommodate the profile of the extruded aluminium material (206).

6. The method as claimed in claim 1, wherein the rotational speed of the hot saw cutter (104) is decreased to increase torque of the hot saw cutter (104) while cutting the extruded aluminium material.
7. The method of claim 2, wherein the fabricating of anode stem further comprises:
chamfering on boring machine;
drilling one or more holes on the anode stem for sleeve fitting; machining one or more sleeves on a lathe machine; and pressing, via a press machine, one or more ends of the anode stem in order to flare the one or more sleeves in hot condition.
8. A system for producing an anode stem, the system comprising:
a casting means (101) for casting a uniformly grained aluminium material (202);
an extruding means (102) for extruding the uniformly grained aluminium material (202) through a feeder die (204) and a bolster (205) to obtain an extruded aluminium material (206) with required profile and length;
a traversing means (103) for traversing the extruded aluminium material towards a hot saw cutter (104) via one or more rollers (207) and one or more pullers (209); and
a cutter (104) to cut the extruded aluminium material, using the hot saw cutter (104), into one or more aluminium pieces of equal length, wherein an aluminium piece of the one or more aluminium pieces indicates an anode stem to be used for supporting an anode in a smelting process.
9. The system as claimed in claim 8, wherein the uniformly grained aluminium
material (202) is casted by hot top casting by establishing air flow levels in moulds to
develop an air-slip in order to cool the aluminium material and to obtain uniformly
grained surface finish on the casted aluminium material (202).

lO.The system as claimed in claim 8, wherein the extruded aluminium material is of a cross section in the range of 40,000 - 50,000 mm2, weight in the range of 120-140 kg/m and length in the range of 2400-2500 mm.