RU84386U1 - ANODE DEVICE FOR ALUMINUM ELECTROLYZER - Google Patents

Abstract

An anode device of an aluminum electrolyzer containing an aluminum busbar, a monolithic steel pin and a copper-aluminum block connected by explosion welding, characterized in that the block is made of a three-layer one, in which between the aluminum and copper layers there is an anti-diffusion layer made of nitrided steel with a thickness of 0.5-0.8 mm, and all layers are interconnected over the entire cylindrical area of the block by simultaneous explosion welding.

Description

The invention relates to ferrous metallurgy and is intended for use in a current-conducting anode device of an aluminum electrolyzer.

A known design of the current-conducting anode device of an aluminum electrolyzer (Metallurgical non-ferrous metals reference book. Aluminum production. - M .: Metallurgy, 1971. - P.178-182), in which the block is made of monolithic aluminum, and the steel pin is made integral, equipped with a copper jacket to improve contact with the aluminum block and reduce the voltage drop, and to save copper, the shirt can be combined: one half of the circumference of the pin is made of copper (copper insert), and the second is made of steel.

The disadvantage of this design is the low strength and reduced service life associated with the gradual deformation of the block and a decrease in its contact area with the copper-steel pin due to the inability of a very ductile aluminum block having low hardness to withstand the significant and long-term pressing forces required to ensure tight contact. Another disadvantage of this design is the significant cost involved in the manufacture of the composite pin, which is associated with the use of a large mass of scarce copper insert (about 6 kg) and expensive welding wire (about 1 kg) for welding a copper insert to a steel pin.

A known design of the current-conducting anode device of an aluminum electrolyzer (US Pat. RF No. 2153028, IPC C25C 3/16, publ. 20.07.2000), when the block and the pressure lever are made of antimagnetic material.

The disadvantage of this design is the high transient electrical resistance due to the lack of tight contact between the pad and the pin and the possibility of its rapid contamination and oxidation during operation, since the lever does not allow the large pressing forces necessary for good contact and provides only a surface less dense contact compared to traditional bolted contact connection. In addition, the service life of the anode device is reduced due to gradual deformation and the presence of a high transient electrical resistance, which is characteristic of a detachable steel-antimagnetic type contact material, the transient electrical resistance of which is much greater than, for example, the most preferred copper-aluminum contact, which means that contact overheating and premature failure of the entire structure.

The closest in technical essence is the design of the current-conducting anode device of the aluminum electrolyzer (US Pat. RF No. 2232831, IPC С25С 3/16, publ. 07.20.2004 Bull. No. 20), in which the pin is made of monolithic steel, and the block is made of bimetallic copper-aluminum with a thickness of the copper layer of 1.2-1.5 mm, which is connected to the aluminum layer by explosion welding over the entire radius and in the sections of the slope of the block, where the width of the copper layer is not less than 0.6 of the width of the slope.

The disadvantage of this design is the decrease in strength and transient electrical resistance associated with the prolonged exposure to high temperatures on the anode device (according to the technical specifications, the unit is in operation for at least 5 years), which leads to the development of diffusion processes and the formation of brittle intermetallic compounds at the aluminum-copper interface, sharply reducing the strength and conductivity of the compound, which is characteristic of a given pair of metals, prone to the formation of chemical compounds at its high temperature urnom heating. Other disadvantages of this design include the increase in the cost of manufacturing blocks associated with the additional costs of expensive copper and explosives required for welding by explosion of copper to aluminum in the areas of the slope of the block, as well as the inability to obtain a high-quality welded joint over the entire contact area of aluminum with copper from due to the formation of a large amount of brittle molten metal on the slope sections of the shoe, which is associated with the use of these traditionally difficult to weld curves in the linear sections of additional detonation initiators from detonating cord segments having a stable detonation velocity but with an ultrahigh brisant action (the detonation cord detonation velocity is ~ 6500 m / s, and the optimum detonation velocity during copper and aluminum explosion welding should be in the range of 1800-2500 m / from).

The technical result that is ensured by the implementation of the invention is an increase in the strength and service life of the anode device, as well as a decrease in transient electrical resistance.

The technical result achieved is achieved by the fact that in the anode device of the aluminum electrolyzer containing an aluminum busbar, a monolithic steel pin and a copper-aluminum block connected by explosion welding, made of a three-layer layer, in which an anti-diffusion layer of nitrided steel 0.5- 0.5 mm thick is installed between the aluminum and copper layers 0.8 mm, with all layers interconnected over the entire cylindrical area of the block by simultaneous explosion welding.

In contrast to the prototype, in the claimed object, the block is made of three layers, which allows to increase the strength and service life of the anode assembly due to the introduction of a third heat-resistant and more durable (compared to aluminum and copper) material that can successfully withstand long-term operational thermal deformation loads.

The implementation of the anti-diffusion layer of nitrided steel allows one to increase thermal strength and maintain a low transient electrical resistance due to the creation of a diffusion barrier in the form of a nitrided layer, which will not allow the formation of brittle intermetallic compounds between aluminum and copper, which sharply reduce the strength and electrical conductivity of the composite.

The implementation of the anti-diffusion layer of nitrided steel with a thickness of 0.5-0.8 mm allows to increase the strength and service life of the anode assembly by creating the ability to successfully withstand significant pressure from the pressing force necessary to ensure tight contact of the block with a steel pin, not plastic copper-aluminum pad layers, and a more durable copper-steel-aluminum composite, which will eliminate the possibility of deformation of such a reinforced composite pad and thereby ensure the constancy of the initial p dimensions of the pads, and hence the constancy of the electrical contact "block-pin" during a long period of operation of the node. When the thickness of the interlayer of nitrided steel is less than 0.5 mm, the strength of the joint decreases due to the formation of welding defects in the form of burn throughs and lack of fusion due to the cumulative effect, which is characteristic of explosion welding of metals of small thicknesses. The thickness of the layer of nitrided steel more than 0.8 mm is not economically feasible due to the increased consumption of nitrided steel, as well as the possibility of deformation of the block due to an increase in the height of the explosive charge, and, consequently, its power.

The implementation of the connections of all layers to each other over the entire cylindrical area of the block allows to increase the strength of the connection by simplifying the shape of the contact copper layer and thereby eliminating its explosion explosion on difficult to weld areas of the slope of the block having a large amount of molten metal. Expenses of expensive copper and explosives will also significantly decrease (by more than 20%) due to the exclusion of the copper layer and explosives necessary in the case of explosion welding in the areas of the slope of the block.

The connection of all layers of the block with simultaneous explosion welding allows to obtain high strength and quality of the welded joint due to the absence of welding defects such as burn-throughs, lack of fusion, melted metal, since, for example, during sequential welding by explosion of each layer of the block (in two explosive operations), defects can be formed such as burn-throughs, lack of fusion, brittle alloys, etc. In addition, simultaneous explosion welding reduces the complexity of manufacturing and the consumption of explosive materials (explosive of substances elektrodetorov, detonation wires) through the use of only one blasting operation.

The invention is illustrated by drawings, where figure 1 shows a General view of the current-conducting anode device of an aluminum electrolyzer, figure 2 is the same, top view.

The anode device of the aluminum electrolyzer consists of an aluminum bus 1, a steel pin 2 and a three-layer block consisting of a main aluminum layer 3, a contact copper layer 5 and an intermediate anti-diffusion layer of nitrided steel 4 with a thickness of 0.5-0.8 mm, all layers being connected between each other over the entire cylindrical area of the block by simultaneous explosion welding, while the block is pressed against the pin with the help of a cover 6, studs 7 and nuts 8, which allows to increase strength, service life of the anode device and reduce transition f electrical resistance due to the creation of a diffusion barrier in the form of a nitrided layer, which will not allow the formation of brittle intermetallic compounds between aluminum and copper, which sharply reduce the strength and conductivity of the composite, and also reduce the complexity of manufacturing and reduce the cost of expensive copper and explosive substances by simplifying the shape of the contact copper layer.

The operation of the anode device of an aluminum electrolyzer is as follows. From the common electric circuit, current is supplied to the aluminum bus 1, then the current passes through a three-layer block, first along the main aluminum layer 3, then through the intermediate anti-diffusion layer of nitrided steel 4 and the copper layer 5, the current is supplied to the steel pin 2, which is immersed in the anode mass of self-calcining anode. During operation of the anode assembly, the block is constantly exposed to prolonged exposure to mechanical stress at high temperatures. Therefore, the design of the current-conducting anode device of an aluminum electrolyzer is subject to increased requirements, which are to provide high strength, durability with minimal transient electrical resistance. These requirements are ensured by the fact that the block is made in three layers, in which an anti-diffusion layer of nitrided steel 0.5-0.8 mm thick is installed between the aluminum and copper layers, and all layers are interconnected over the entire cylindrical area of the block by simultaneous explosion welding.

Assembly of the proposed design of the anode assembly of an aluminum electrolyzer occurs in the following sequence. First, the manufacture is carried out by simultaneous explosion welding of a three-layer block. For this, a three-layer package is assembled so that the anti-diffusion layer of nitrided steel is between the aluminum and copper layers, while the explosive charge is placed on top of the contact copper layer. The three-layer (copper-steel-aluminum) block obtained by simultaneous explosion welding is fusion-welded to an aluminum rail. Then, the three-layer block is docked with the steel pin directly on the aluminum electrolyzer, while in order to ensure a stable tight electrical contact, the block from the side of the copper layer is pressed against the steel pin with the help of plates, studs and nuts.

Execution example

The starting materials for the manufacture of the current-carrying anode device were: a pin made of steel of grade St.3 with a diameter of 120 mm; A5 standard aluminum block 110 × 200 mm in size and 60 mm in radius; anti-diffusion layer of nitrated steel grade St.3 with a thickness of 0.2-1.0 mm; 1.5 mm thick copper interlayer; A5 standard aluminum tire with a cross-section of 35 × 310 mm.

At the first stage, the production of three-layer (copper-steel-aluminum) blocks by simultaneous explosion welding was carried out. In this case, the thickness of the anti-diffusion layer of nitrided steel varied from 0.2 to 1.0 mm. Obtained by explosion welding, composite pads with different thicknesses of nitrided steel layer were cut into samples for mechanical tests, metallographic and electrophysical studies. Data on the effect of the thickness of the anti-diffusion layer on the strength, the number of melts and the transient electrical resistance of a three-layer block are given in Table 1. The obtained research results showed that the optimal thickness of the anti-diffusion layer of nitrided steel is 0.5-0.8 mm. With such a thickness of the anti-diffusion layer, the highest bond strength (σ _com. = 107-108 MPa) and the lowest transient electrical resistance (R = 8-10 μOhm · mm ² ) are achieved. When the thickness of the interlayer of nitrided steel is less than 0.5 mm, there is a decrease in strength and an increase in transient electrical resistance due to the formation of welding defects such as burn-throughs, lack of fusion, brittle alloys, which is typical for explosion welding of metals of small thicknesses. The thickness of the layer of nitrided steel more than 0.8 mm is not economically feasible due to the increased consumption of nitrided steel, as well as the possibility of deformation of the block due to an increase in the height of the explosive charge, and, consequently, its power.

Table 1 The effect of the thickness of the nitrided steel layer on the number of melts, bond strength and transient electrical resistance The thickness of the nitrided steel layer, mm Materials to be welded Consumption of nitrided steel layer, kg The presence of welding defects The amount of molten metal,% The strength of the connection, MPa Transient electrical resistance, μOhm × mm ² 0.2 M1 + St. 3 (nitrogen.) + A5 0,028 Burns, lack of fusion 48 54 56 0.3 M1 + St. 3 (nitrogen.) + A5 0,042 Burns, lack of fusion 27 68 37 0.4 M1 + St. 3 (nitrogen.) + A5 0.056 Local Burns fourteen 88 21 0.5 M1 + St. 3 (nitrogen.) + A5 0,070 no 6 107 10 0.6 M1 + St. 3 (nitrogen.) + A5 0,084 no 5 108 8 0.7 M1 + St. 3 (nitrogen.) + A5 0,098 no 5 108 8 0.8 M1 + St. 3 (nitrogen.) + A5 0,112 no 5 108 8 0.9 M1 + St. 3 (nitrogen.) + A5 0.126 no 6 107 10 1,0 M1 + St. 3 (nitrogen.) + A5 0.140 no 5 108 8

table 2 Comparative data on thermomechanical tests and electrophysical studies of anode devices of various designs Controlled object Materials to be welded Thickness of materials to be welded, mm Consumption of materials, kg Pads properties after explosion welding Pads properties after explosion welding and heat treatment (Т = 300 ° С, t = 3 h) copper nitrided steel explosive The amount of molten metal,% Bond strength,
MPa Transient electrical resistance μOhm × mm ² The number of charges and inter-lead,% The strength of the connection, MPa Transient resistance μOhm × mm ² Proposed M1 + St. 3 nitrogen. + A5 1.5 + 0.6 + 80 0.240 0,084 0.180 5 108 8 7 106 12 Prototype (RF Patent No. 2232831) M1 + A5 1,5 + 80 0.294 - 0.220 eleven 92 17 100 (continuous layer) 46 104

Comparative data of thermomechanical tests and electrophysical studies of various designs of the anode device are given in table 2. The obtained research results showed that the proposed design of the anode device in comparison with the prototype has higher strength and durability with minimal transient electrical resistance.

Claims (1)

An anode device of an aluminum electrolyzer containing an aluminum busbar, a monolithic steel pin and a copper-aluminum block connected by explosion welding, characterized in that the block is made of a three-layer one, in which between the aluminum and copper layers there is an anti-diffusion layer made of nitrided steel with a thickness of 0.5-0.8 mm, and all layers are interconnected over the entire cylindrical area of the block by simultaneous explosion welding.