RU2635117C2 - Method for refining magnesium and its alloys - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes introducing the refined metal throgh poring tube into the molten flux furnace, which specific gravity is greater than the specific gravity of the refined metal, and passing the metal through said layer. The refined metal is introduced into the upper part of the molten flux layer to a depth of not more than 1/3 of layer height and is directed horizontally with stream at a molten flux temperature in the injection zone within the range of 270-730°C.

EFFECT: invention provides release of produced magnesium or its high-quality alloy at higher processing rates than when pouring magnesium raw material into magnesium layer of refinery furnace casting chamber, and simplifies the design of the refinery furnace, increases the service life of the interservice period and simplifies its maintenance.

2 dwg

Description

The invention relates to the field of non-ferrous metallurgy, in particular to the development of refining technology for magnesium and its alloys.

A known method of refining raw magnesium in continuous refining furnaces. (VI Shchegolev, OA Lebedev. Electrolytic production of magnesium. Moscow. Publishing house "Ore and metals", 2002).

In the known method, raw magnesium from the electrolysis compartment in vacuum ladles is transported to the refining furnace and poured into the refining chamber into the filling chamber through a pouring pipe located on the furnace floor. At the bottom of the furnace is a molten flux. Refining of magnesium is carried out by settling for 30-50 minutes, that is, the natural deposition of non-metallic impurities and iron due to the difference in the densities of impurities, liquid magnesium and flux in the furnace in the lower part of its volume.

The difference in the densities of flux and liquid magnesium allows it to remain on the surface of the flux throughout the refining period.

During refining, magnesium oxide, nitride, and the resulting intermetallic compounds settle on the bottom of the furnace.

Chlorides contained in raw magnesium (electrolyte of electrolysis baths) adsorb particles of nitride and magnesium oxide during precipitation into the molten salt, which are then deposited on the bottom of the furnace.

Magnesium oxide, nitride and intermetallic compounds accumulated on the bottom of the furnace in the salt composition layer are periodically removed from it using a special technological tool.

The disadvantage of this method is the low quality of the refining of magnesium oxides (MgO) and intermetallic compounds (Mg ₃ N ₂ ), since the purification of raw magnesium is carried out only by settling. It is known that magnesium cannot be purified from fine particles of MgO and Mg ₃ N _{2 by} settling for, for example, 60 minutes. A longer exposure is irrational due to a significant decrease in furnace productivity.

A known method of introducing a refined alloy under a layer of a flux heavier than the alloy, as a result, the alloy spontaneously passes through the flux layer, refines, floats to the surface and is removed. (USSR author's certificate 355242.)

The supply of raw magnesium or its alloy under the flux layer is due to the action of hydrostatic pressure of the magnesium column.

When the next portion of magnesium is supplied, it passes (sparges) through the flux layer of the second chamber and is removed. Impurities of non-metallic inclusions are wetted and deposited on the bottom of the mixer in the form of sludge.

This method is adopted as a prototype.

The disadvantage of the method of refining magnesium and its alloys, adopted as a prototype, is that with each subsequent input of magnesium, it comes into contact with impurities deposited in the sludge, lifting them into the volume of the layer of refined magnesium.

This contributes to the possibility of non-metallic inclusions entering refined magnesium in increased quantities, which ultimately reduces the quality of finished products made from alloys with a high content of non-metallic inclusions.

The objective of the invention is to obtain a method of refining magnesium and its alloys, which allows to reduce the content of non-metallic inclusions in magnesium ingots and its alloys and to exclude the possibility of magnesium oxide from flux entering the castings of magnesium products.

The problem is solved in that in the method of refining magnesium and its alloys from non-metallic inclusions by passing through a layer of molten flux with a specific gravity greater than the refined metal, magnesium is introduced into the flux layer to a depth of not more than 1/3 of the height of the flux layer, while the temperature of the flux layer in the metal entry zone is maintained within 720-730 ° C.

Metal is introduced into the flux layer by a horizontal stream.

In FIG. 1 shows a furnace for implementing the method.

In FIG. 2 shows the lower end of the magnesium fill pipe.

The method is as follows.

Raw magnesium through the pouring pipe 1 from the ladle is poured into the furnace into a flux 2 in the upper part to a depth of not more than 1/3 of the salt flux layer height, while the flux temperature should be maintained within 720-730 ° С to maintain optimal conditions of separation from the metal non-metallic impurities and their deposition on the hearth of the furnace. The raw magnesium is poured into the furnace and the magnesium is taken for casting independently. Refined magnesium is taken from the furnace for casting into ingots through a sampling pipe 3. Express analysis of refined magnesium is performed before it is drained from the furnace to a conveyor or to a mold. The metal from the furnace is taken with a sampler and poured into a chill mold for casting samples 15 minutes before the metal is taken. Depending on the operating mode of the furnace, sampling for analysis of the composition of magnesium is carried out 3-4 times per shift.

Cleaning the furnace from sludge is carried out 1 time in three days. The shaft cover is opened for servicing the furnace 4 and, using a clamshell tool, the sludge settled on the bottom is removed from the furnace. Then, if necessary, an operation is performed to adjust the composition of the flux layer to restore a given chemical composition and its volume.

The set temperature in the flux layer is maintained in automatic mode by changing the current load on the electrodes 5.

Raw magnesium is introduced into the layer of molten salt by a stream directed horizontally. For this, the drain pipe is plugged in the zone of magnesium exit, and on its side surface there is an opening 6.

The design of the lower end of the casting pipe 1 shown in FIG. 2, provides the exit from it of raw magnesium into the flux layer horizontally, which eliminates the agitation of the flux in the lower part and this eliminates the re-entry of non-metallic inclusions into the refined metal.

Using the method allows for the release of the resulting magnesium or its high quality alloy at higher technological parameters than when pouring raw magnesium into the magnesium layer of the casting chamber of the refining furnace.

In addition, the use of the proposed method will simplify the design of the furnace for refining, increase the period of the overhaul period of operation and simplify its maintenance.

Claims (1)

A method for refining magnesium and its alloys from non-metallic inclusions, comprising introducing refined metal using a casting tube into a molten flux furnace, the specific gravity of which is greater than the specific gravity of the refined metal, and passing the metal through said layer, characterized in that the refined metal is introduced into the upper part of the molten flux layer to a depth of not more than 1/3 of the layer height by a horizontally directed jet at a temperature of molten flux in the input zone within 720-730 ° C.

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