RU2325470C2 - Anode holder and its manufacture method - Google Patents

Abstract

FIELD: metallurgy; electric treatment.

SUBSTANCE: said utility invention relates to the non-ferrous metallurgy, in particular, to an anode holder and its manufacture method and may be used during production of aluminium and magnesium in electrolytic cells using the electrolytic method. The anode holder contains a current-carrying aluminium rod rigidly connected with a steel cross bar by fusion welding, using a bimetallic adapter. The adapter is located between the ends of the rod and the cross bar; the adapter welding areas being equal to the rod and cross bar welding areas. The anode holder manufacture method involves the connection of the current-carrying aluminium rod to the steel cross bar by fusion welding using an adapter. Electron beam welding is used; the adapter is located between the ends of the rod and the cross bar, the welding areas of the adapter is being equal to the welding areas of the rod and the cross bar.

EFFECT: anode holder with high performance characteristics.

2 cl, 1 dwg

Description

The claimed technical solution - the holder of the anode and the method of its manufacture - relates to the field of non-ferrous metallurgy and can be used in the production of aluminum and magnesium by the electrolytic method in electrolyzers.

A technical solution is known [1] - a method for connecting a current path (anode holder) of an electrolyzer to produce aluminum in electrolysis. To connect the electrolyzer current path, the current conductors are placed in the potential of an external magnetic field, after which fusion welding is performed. Welding is carried out by alternating current of increased frequency up to 20,000 Hz with the creation of an additional magnetic field in the welding zone.

This technical solution is aimed at reducing energy consumption by reducing the resistance of the connection (contact) of the conductors, i.e. weldable parts. However, when welding conductors of large thicknesses, up to 200 mm, their middle part is often not penetrated. This is a hotbed for increasing the electrical resistance of the current lead and, as a result, an increase in energy losses.

Also, during the operation of the electrolyzer, a large amount of heat is released from the bath, the conductors are constantly in the zone of elevated temperature. In addition, from the passage of high-density current, the conductors are heated. As a result of this, the undigested portion is corroded, and under the influence of high voltage and the presence of a fracture of the joint, eddy currents arise, which, in interaction with temperature, form electrocorrosion. Over time, the process of fracture of a welded joint is accelerated and has a direct relationship - the larger the fracture zone, the faster the overall process of corrosion of the joint. The area of the destruction site increases, and the area of the connection decreases. Under its own weight, the lower part of the current lead, that is, a traverse with contact elements, breaks off and goes into the molten bath. The melting process of aluminum is terminated.

It takes a long time to restore the process. In addition, in the disclosure and in the example of a specific embodiment of the invention, a method is described that can be performed directly where the electrolyzers work and create the main external magnetic field (OMPF) by the conductive elements.

To conduct the process of welding with alternating current with a frequency of up to 20,000 Hz in the weld formation zone, it is necessary to create an autonomous additional magnetic field (DCM). which prevents the ejection of molten metal from the weld zone, the so-called hydrodynamic effect.

To create DCM, a power source is needed, which is calculated, selected in details according to the scheme and completed in a single device. This amounts to certain costs. In addition, it is harmful and dangerous for a person to repair breakdowns in current leads (anode holders) under elevated temperatures and in the presence of magnetic fields.

A known construction of the anode holder [2], containing an aluminum rod and a steel bracket (traverse) connected by aluminum plates mounted on opposite sides of the rod and the steel bracket. The plates are attached to the aluminum rod by electric arc welding, and to the steel bracket by explosion welding. The disadvantage of this design is the small cross section of explosion-welded plates that work under tension at high ambient temperatures and the holder itself, which is heated by the action of transmitted electricity. As a result - low operational ability and high power consumption.

A known construction of the anode holder [3], containing an aluminum rod and a steel bracket (traverse) with a groove connected on the sides by bimetallic plates (aluminum-steel) with a protrusion. The plates are also attached to the aluminum rod by electric arc welding, and the plates are connected to the steel bracket by means of their protrusions in the groove and fixed by arc welding.

This design requires increased energy consumption due to poor contact between the bimetallic plate and the non-welded sections of the bracket. In addition, when welding aluminum with aluminum and steel with steel, the dissimilar metals of the bimetallic plate are delaminated, resulting from significant shrink stresses.

Also known is the design of the anode holder [4], containing an aluminum current-supply rod rigidly connected to a steel beam with a groove. A rod is located in the groove, on both sides of which there is a bimetallic insert. The contact surfaces of the joints of dissimilar metals of the insert form an angle with the vertical. On both sides of the insert is fixed by arc welding to the rod and traverse. As in the previously described technical solution, in this one, the adjacent surfaces of aluminum to aluminum and steel with steel have large undeveloped areas.

The disadvantage of this design is the loss of electricity due to the large contact resistance of the non-welded sections. In addition, when welding an adapter with an aluminum rod and a steel beam, a high temperature is created that negatively affects the connection of dissimilar metals (aluminum-steel). So, the cause of the destruction of the anode holders is the formation of brittle intermetallic compounds at the boundaries of the compound of dissimilar metals that occur at temperatures (even short-term) above 250 ° C.

The tendency of the embrittlement to embrittlement is also observed at lower temperatures, 150 ° С under the condition of long exposure. This danger remains during the thermal action of the welding source during welding to the adapter of the anode holder elements, and the use of arc welding is especially dangerous in this case. This is primarily due to the fact that arc sources do not allow heat to be focused in a narrow place, but large volumes of nearby metal are heated at the welding site. It follows that the anode holders made according to these sources have low mechanical and electrical characteristics.

To eliminate these drawbacks, the task was to create an anode holder that provides a reliable connection of the rod with the traverse and ensures minimal energy loss during the passage of current.

The problem is solved by the created design of the anode holder and the method of its manufacture.

The proposed design of the anode holder, as well as the known one, contains a conductive aluminum rod rigidly connected to the steel traverse by means of a bimetallic adapter.

Unlike the known technical solution, the adapter is located between the ends of the rod and the beam, while the areas for welding the adapter are equal to the areas for welding the rod and the beam.

A method of manufacturing an anode holder, as well as in the known technical solution, involves fusion welding of a rod with an adapter and a beam with an adapter.

In contrast to the known technical solution, welding is performed in a vacuum by an electron-arc method.

Thus, the distinguishing features have a number of positive qualities that affect the technical result, namely:

- the adapter is located between the ends of the rod and traverse. Since the rod is made of aluminum, and the beam is made of steel, the placement of the adapter between them makes it possible to simplify the design of the anode holder;

- the area for welding the adapter is equal to the areas for welding the rod and traverse. This indicates that the adapter, consisting of two dissimilar metals, has, for example, flat welding areas. The same areas for welding have a rod and a traverse. This feature allows you to achieve the effect of electric power transmission over the entire area of the end of the rod through the entire area of the adapter of the entire end area of the beam. This means that all adjacent conductive and transmitting areas are flat and do not have grooves, bulges or depressions;

- welding is performed in vacuum by electron beam welding, which ensures high-quality welding of homogeneous metals due to the focused beam, which achieves a high melting point of metals and maintaining the molten bath in a small volume. In addition, electron beam welding allows welding of adjacent parts at high speed (10 mm / sec). At this speed, the heating zone of the welded parts is very small. This means that the temperature of the adapter in the zone of the connection "aluminum-steel" reaches low short-term values (100-120 ° C). This temperature does not contribute to the formation of foci of destruction (intermetallic compounds) of the aluminum-steel compound of the bimetallic adapter. In addition, electron beam welding is carried out in vacuum without oxygen. The metal boiling in the molten bath does not oxidize, and the gases emitted are constantly removed, which ensures the compaction of the molten metal, and hence the weld.

The distinguishing features listed above are necessary and sufficient to solve the task. All the distinguishing features are in a causal relationship with the result obtained and allow at a high technical level to create a design and implement a method of manufacturing the anode.

The essence of the technical solution is that when fusion welding aluminum rods and steel yokes, a bimetallic adapter is used, which is welded to the rod end with one side and the yoke at the other end, that is, in the butt. In this case, welding is performed in vacuum by an electron beam.

The essence of the technical solution is illustrated by the drawing.

The drawing shows a section of the connection of the rod with the traverse.

The anode holder includes a rod 1 of aluminum and a traverse 2 of steel. Between the end of the rod 1, the end of the traverse 2 is a bimetallic adapter. One side of adapter 3 is aluminum, the other side 4 is steel. In the drawing, arrows indicate electron beam welding, and thin lines indicate the welding zone.

In accordance with the proposed manufacturing method, the connection (assembly) of the anode holder is carried out in this sequence.

A bimetallic adapter with steel (12X18H10T) side 4 was placed on a vertically mounted crosshead 2 (steel 20L) and pre-fixed by manual argon-arc welding from two opposite sides. After that, the aluminum (A7) rod 1 was installed on the aluminum (A) side 3 of the adapter and, from two opposite sides, the aluminum rod 1 was also preliminarily fixed by argon-arc welding. The preliminary mounting of the beam, adapter and rod was carried out with a gap of not more than 0.1-0.3 mm between the areas to be welded, while the areas to be welded together are equal.

The final fastening of the traverse, adapter and rod was carried out from two loose sides (with reinstallation) by electron beam welding in a vacuum of 10 ^-4 mm Hg, providing guaranteed penetration due to single-pass welding in 2/3 of the thickness of the working section.

To perform the process of connecting the anode holder, the following modes of electron beam welding at a voltage of 60 kV were used:

- for steel:

welding current - 550 mA,

focusing current - 710 mA,

welding speed - 600 mm / min,

Sweep: amplitude - 1.5 mm (transverse)

frequency is 100 Hz;

- for aluminum:

welding current - 330 mA,

focusing current - 720 mA,

welding speed - 600 mm / min,

sweep: amplitude - 2 mm (transverse)

frequency - 200 Hz.

Thus, high-quality welds were obtained without changing the structure of the metals being welded in the heat-affected zone. The width of the weld is within 2-5 mm.

The proposed manufacturing technology of anode holders using electron beam welding allows you to master the production of a new design of the anode holder, which consists in the end connection of the rod, adapter and traverse. This is achieved by welding with a highly focused beam of high power, which ensures complete penetration of the parts to be joined across the entire section (90 × 200), without cutting edges, without the use of filler materials, without oxidation of the weld and with metal heating in the aluminum-steel joint zone bimetallic adapter below the temperature of formation of intermetallic compounds.

This method of manufacturing the anode holder provides a minimum residual voltage that does not cause deformation and destruction of the bimetallic adapter. As shown by mechanical and electrical tests, finished products have high performance characteristics. The DC voltage drop between the boom and the beam at a current of 500 A did not exceed 1.5 mV.

Information sources

1. RF patent No. 2034098, IPC С25С 3/16.

2. A.C. USSR No. 395507.

3. A.S. USSR No. 751174.

4. RF patent №2075553, IPC С25С 3/12 - prototype.

Claims (2)

1. The anode holder containing a current-supplying aluminum rod, rigidly connected by fusion welding with a steel traverse by means of a bimetallic adapter, characterized in that the adapter is located between the ends of the rod and the beam, while the areas for welding the adapter are equal to the areas for welding the rod and beam. 2. A method of manufacturing an anode holder, comprising connecting a current-supplying aluminum rod to a steel beam with fusion welding using a bimetallic adapter, characterized in that the welding is carried out in vacuum by electron beam welding with the adapter located between the ends of the rod and the beam, while the areas for welding the adapter are equal to the areas for welding rods and traverses.