RU197407U1 - Device for refining liquid metals and alloys - Google Patents

Abstract

The technical solution relates to metallurgy, and in particular to devices for refining liquid metals and alloys, mainly aluminum. The use of the inventive device can improve the efficiency of refining liquid metals and alloys on the way to the foundry machine, as well as improve casting performance and equipment reliability. This is achieved by placing in the channel part of the device, namely in the vertical channels of removable sleeves, in which the inner surface is ribbed. When electric current is passed through the melt to heat it, non-metallic inclusions are removed from it by deposition on the inner surfaces of the removable bushings and in the filter installed at the outlet of the channel part. The possibility of using removable sleeves and, if necessary, replacing them quickly reduces downtime and, consequently, improves the performance of the refining device and the reliability of the transport channel. 3 ill.

Description

The technical solution relates to metallurgy, and in particular, to devices for refining liquid metals and alloys, mainly aluminum.

It is known that in smelting and foundry metal alloys are produced in smelters or mixers by mixing primary metal with alloying elements.

The tendency of aluminum and its alloys to combine with oxygen leads to the formation of a very strong oxide film on its surface. The amount of oxide increases with increasing temperature, as well as with an increase in the content of water vapor in the atmosphere. When alloying, mixing, and removing slag, oxides can pass into the melt and can be found in castings.

In the liquid state, aluminum also has an increased ability to dissolve hydrogen, which is formed by the interaction of liquid aluminum with water vapor. The sources of water vapor formation can be the moisture content of charge materials, furnace linings, and air humidity. The presence of hydrogen in the melt leads to the formation of pores in the castings, which reduces their strength [1].

One of the most effective ways to solve the problem of obtaining the required final impurity content in the castings is the refinement of alloys. Therefore, liquid metal (melt) from the mixer furnace through the transport chute enters the after-furnace refining units for degassing and filtration and then goes to a casting machine for crystallization.

Refining of the melt should be carried out immediately before the casting machine, as the efficiency of processing too early during the process is reduced by subsequent processes during transportation.

One option for refining may be degassing. Two processes of degassing the melt are possible: melt standing in a neutral gas medium or purging (sparging) of it with a neutral gas. Bubbling is a more profitable process as compared to aging: at the same specific gas flow rate it provides a higher degree of hydrogen removal or, with an equal degree of removal, saves refining gas [2].

An effective method of refining aluminum and its alloys from non-metallic inclusions suspended in the melt is also filtering. The essence of filtering consists in passing molten metal through filters made of materials that are neutral or active with respect to it [3].

When filtering through mesh materials, the mechanical separation of inclusions on the mesh filter occurs. Unfortunately, these filters delay only large inclusions, and small ones pass.

The operation of refining plants at metallurgical enterprises revealed their advantages and disadvantages. The main advantage of these plants is a significant improvement in the quality of the alloys produced, the disadvantage is low reliability and high maintenance costs.

It is known that when moving along a transport chute, especially over long distances, the temperature of the melt decreases significantly, so sometimes it is necessary to heat the melt in the transport chute. Indirect heating is known - when the heating element heats the transport channel itself through heat transfer, through which the molten metal flows [4], and direct heating - when the electric current is passed directly through the melt, thereby heating it [5]. The disadvantage of these devices is that they do not include refining of the melt.

Closest to the claimed device is an induction unit for refining aluminum melts [6], installed in the transport chute between the mixer and the casting machine (mold), which contains two vertically arranged cylindrical channels connected from above and below by horizontal channels, a partition installed in the upper horizontal channel, ceramic foam filter and refining gas injection system (hereinafter referred to as a device for refining liquid metals and alloys).

The disadvantages of the known device include the following:

- low reliability of the ceramic foam filter, since all non-metallic inclusions pass through it and quickly clog it;

- during operation, the vertical channels are overgrown with oxides, and their cleaning or replacement is required, which leads to forced downtime and, as a result, to a decrease in productivity.

The new technical solution is based on the task of increasing the efficiency of refining, as well as increasing the productivity of the device for refining.

The problem is solved in that in a device for refining liquid metals and alloys, including a vertically arranged receiving and distributing cylindrical channels connected above and below the respective horizontal channels, a partition installed in the upper horizontal channel, a filter located above the distributing cylindrical channel, and the system refining gas inlet, according to a new technical solution, removable bushings are placed in the receiving and distributing cylindrical channels, internal rotation which are made ribbed.

With induction excitation of electric current in the channels, the partition installed in the upper horizontal channel is made of electrically conductive material.

When conductive excitation of an electric current in the channels, the partition installed in the upper horizontal channel is made of non-conductive material.

In FIG. 1 presents the inventive device for refining liquid metals and alloys, FIG. 2 - the claimed device for refining with induction excitation of electric current in the channel part, in FIG. 3 - the same with the conductive excitation of an electric current in the channel part.

The device for refining liquid metals and alloys contains two vertically arranged cylindrical channels - receiving 1 and distributing 2. These channels are connected above and below by horizontal channels 3 and 4, respectively. In the upper horizontal channel 3, a partition 5 is installed, dividing it into two compartments. At the exit of the dispensing compartment, a filter 6 is installed above the vertical channel 2 (for example, from ceramic foams). Inside the vertical channels 1 and 2 between the horizontal channels 3 and 4, removable sleeves 7 ₁ and 7 ₂ are placed, respectively, while the inner surface of these sleeves is ribbed. Also in the receiving vertical channel 1 is a refining gas input system in the form of a pipe 8 with nozzles 9 in its lower part.

In the refining device during the induction excitation of electric current in the channel part (Fig. 2), the partition 5 installed in the horizontal channel 3 is made of electrically conductive material (for example, graphite) to form a circuit closed for electric current, similar to the channel part of the induction unit of the melting furnace. In this case, at least one of the vertical channels is covered by an inductor 10 with a closed magnetic circuit 11.

In the case of conductive excitation of electric current in the channel part (Fig. 3), the partition 5 installed in the horizontal channel 3 is made of non-conductive material. At the same time, the transport chute from the side of the entrance to the receiving channel 1 and from the side of the exit from the dispensing channel 2 has one section each, in the lining of which electrically conductive bodies 12 are mounted with the possibility of their contact on the one hand with the molten metal, and on the other hand, with the current-carrying bus 13 connected to the secondary winding of the transformer 14.

The operation of the claimed device for refining can be explained as follows.

In the presence of an electric current in a melt unit, energy is released per unit time:

и

- векторы плотности тока (А/м²) и напряженности электрического поля (В/м);Where

and

- vectors of current density (A / m ² ) and electric field strength (V / m);

и

- векторы скорости (м/с) расплава и действующей на него удельной электромагнитной силы (Н/м³);

and

- velocity vectors (m / s) of the melt and the specific electromagnetic force acting on it (N / m ³ );

- модуль плотности тока, А/м²;

- current density modulus, A / m ² ;

σ is the conductivity of the melt, Ohm ^-1 * m ^-1 ;

The first term on the right-hand side of (1) determines the thermal energy, and the second term determines the mechanical work performed in the melt when an electric current flows.

The specific electromagnetic force in the melt is defined as:

- вектор магнитной индукции, Тл.Where

- vector of magnetic induction, T.

If a direct current I flows in a cylindrical conductor with radius R, then

- единичный вектор, направленный по радиусу проводника, а величина ƒ_r определяется в [7] какWhere

is the unit vector directed along the radius of the conductor, and the quantity ƒ _r is defined in [7] as

where μ ₀ = 4π⋅10 ^-7 GN / m.

The Archimedean force acts on a particle in the melt:

- ускорение свободного падения, м/с²,Where

- acceleration of gravity, m / s ² ,

γ is the density of the melt, kg / m ³ ,

γ ₁ and V ₁ - density, kg / m ³ and particle volume, m ³ , respectively.

In addition to the force (4), an additional force acts on the particle caused by the flow of electric current through the melt, which in [5] is defined as

where k is an empirical coefficient equal to 0.75.

направлена к центру проводника, а сила, выталкивающая частицу на поверхность, направлена противоположно.Here, the minus sign indicates that the specific electromagnetic force

directed toward the center of the conductor, and the force that pushes the particle to the surface is directed opposite.

Thus, passing an electric current through the melt facilitates the expulsion of non-metallic inclusions and gas bubbles from it.

During the induction excitation of electric current (Fig. 2), the liquid metal enters the receiving compartment of the refining device through the transport chute. After filling the entire channel part of the refining device with the melt, an inductor 10 is connected to the AC mains; as a result, an electric current I ₂ arises in the liquid metal filling vertical 1, 2 and horizontal 3 and 4 channels, which closes through a partition 5 made of electrically conductive material (for example , from graphite). The direction of current I _{2 is} shown by a dashed line. The appearance of an electric current leads to an increase in the temperature of the liquid melt in the channel part, i.e. allows you to heat the melt in front of the casting machine.

The internal sections of the removable bushings 7 installed in the vertical channels 1 and 2 are smaller than the sections of the horizontal channels 3, 4. In accordance with (3), the electromagnetic force compressing the metal is inversely proportional to the radius of the conductor of the third degree (1 / R ³ ), and therefore , and the force pushing non-metallic inclusions onto the surface of the conductor, according to (5), will be greater in these sections than in other sections of the channel part. As the melt moves along the vertical channels, non-metallic inclusions will settle on the ribbed surfaces of the removable bushings 7. The inert or active gas introduced into the channel 1 through the pipe 8 and nozzles 9 is dispersed into small particles and, moving in the melt stream and colliding with non-metallic inclusions, carries (floats) them to the surface, thereby increasing the efficiency of refining.

The melt flow diagram is shown in FIG. 2 by arrows, most of the non-metallic inclusions settle on the ribbed surfaces of the removable sleeves 7, the rest remains in the filter 6. After the casting is completed, the filter element 6 and the removable sleeves 7 are removed, and they are cleaned or replaced before the next casting.

When conductive excitation of electric current in the channel part of the device for refining (Fig. 3) works as follows. After filling the channel part with liquid metal, the primary winding of the transformer 14 is connected to an alternating voltage network. In the electric circuit, including the secondary winding of the transformer 14 connected in series, the supply bus 13, the sections of the transport chute with the electrically conductive body 12 and the metal melt, an electric current I ₂ arises in the channel part of the refining device and closes along the vertical channels 1.2 and the lower horizontal channel 4 In this case, the metal melt is heated to the required temperature and the non-metallic inclusions settle on the inner surfaces of the removable sleeves 7 and in the filter 6.

After casting is completed, the filter element 6 and removable sleeves 7 are removed, and before the next casting they are cleaned or replaced.

Thus, the claimed device for refining has the following advantages over the known:

- The refining efficiency is increased by passing an electric current through the melt to heat the melt and at the same time removing non-metallic inclusions from it by depositing them on the inner surfaces of the removable sleeves and in the filter.

- The possibility of using removable sleeves and, if necessary, their quick replacement allows to reduce downtime, and, consequently, increase the performance of the refining device and the reliability of the transport channel.

This was confirmed by NPC Magnetohydrodynamics LLC during experiments with refining and heating of aluminum melt in a pilot plant for producing a continuous billet of aluminum alloy. The passage of electric current through the melt in the transport chute made it possible to obtain a cast billet that meets the necessary quality requirements.

Sources of information

1. Gases and oxides in aluminum deformable alloys: Dobatkin VN [et al.] - Moscow: Metallurgy, 1976. - 263 p.

2. Makarov G.S. Refining aluminum alloys with gases / Makarov G.S. - Moscow: Metallurgy, 1977. - 240 p.

3. Kurdyumov A.V. Flux processing and filtering of aluminum melts / Kurdyumov A.V. - Moscow: Metallurgy, 1980 .-- 196 p.

4. Application for invention 2006122205/02, December 7, 2004

5. Patent for utility model No. 192356. Transport chute of a casting complex for liquid metal casting. 12/03/2018

6. Thesis Ph.D. Marakushin NP: Induction installation for refining aluminum melts 05.09.03. - Krasnoyarsk, 2002 .-- 175 p.

7. Shapiro V.E. The action of electromagnetic forces during intense induction heating of a liquid metal in channels. Preprint IFSO-6F, Institute of Physics named after L.V. Kirensky SB AS USSR, Krasnoyarsk, 1972, 26 pp.

Claims (2)

1. A device for refining liquid metals and alloys, containing vertically arranged receiving and distributing cylindrical channels connected above and below the respective horizontal channels, a partition installed in the upper horizontal channel, a ceramic foam filter placed above the distributing cylindrical channel, and a pipe installed in the receiving channel with nozzles for introducing refining gas, characterized in that it is equipped with an inductor with a closed magnetic circuit, made with the possibility of coverage and one of the vertically arranged cylindrical channels, and in the receiving and distributing cylindrical channels are removable sleeves, the inner surface of which is ribbed. 2. A device for refining liquid metals and alloys according to claim 1, characterized in that the partition installed in the upper horizontal channel is made of electrically conductive material.

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