Method for reprocessing of junks of magnesium containing based-based alloys

FIELD: non-iron metallurgy, in particular reprocessing of aluminum waste.

SUBSTANCE: claimed method includes junk charge into premelted flux at ratio of 1:(5-10); heating up to melt temperature; smelting under flux layer, and separation of metal from flux. Equimolar mixture of sodium chloride and potassium chloride with addition of 2.9-52.6 % (in respect to total flux weight) magnesium fluoride is used as flux, and in melting process flux layer with thickness of 4.5-20 cm is maintained. Method affords the ability to conserve original composition and eliminate additional burdening with magnesium.

EFFECT: decreased burn-off loss, especially for magnesium, metal of improved quality.

4 cl, 3 tbl, 5 ex

The invention relates to ferrous metallurgy, in particular to a method of recycling aluminum.

A known method of melting alloy ALC in induction furnaces IAT-2,5 (Kimstach G.M. Preparation of secondary aluminum alloys of chips at machine-building plants. Foundry, 1981, No. 1, p.14-15).

Flux consumption is 2 to 2.5%. Good results provides a flux of 47% KCl, 30% such as NaCl, 23% Na₃AlF₆. The frenzy of metal smelting is ~22%.

To improve the quality at 740°With the crucible wall clear of flux, slag is removed from the furnace and on the surface of the bath serves to 1.5% of the flux. Upon melting of the flux melt is treated with hexachloroethane, which introduce 0.1% of the mass of trunks with a total flow rate of 0.7-0.8%.

This method does not ensure the preservation of Mg in the melt, as it interacts with cryolite and withdrawn from the melt. In addition, the use of volatile hexachlorethane affects the environmental conditions during the melting chips. A small amount of refining flux is mixed with oxides and after melting the flux is completely removed from the metal surface, i.e. the flux single use.

There is a method of melting in saline raw materials containing aluminum and metal inclusions. Raw materials as well as waste and scrap of aluminium alloys brands AL 34 AL 104 (maöan A.G., znakov A.A. Melt in saline raw materials containing aluminum and metal inclusions. The book “Light alloys in the national economy”, 1975, str-181).

When you melt into light fluxes, i.e. with a specific gravity less than that of aluminum, the highest degree of extraction of aluminium (98%) is achieved at 780-800°with the use of fluorspar.

The consumption of flux is: for composition KCl+NaCl+ cryolite - 0.5 kg/kg of the charge, and for the composition of KCl+NaCl+Caf₂- 0.28 kg/kg of charge. In the first case, the rate of melting of 27 g/min, the second 34 g/min

The disadvantage of this method is the same as in the previous case, cryolite interacts with magnesium and impoverishes them alloy. It also requires a large consumption of flux.

The closest in technical essence is a way of scrap aluminum alloys (RF patent No. 2089630, Appl. 30.04.93,, publ. 10.09.97, BI No. 25, 1997, s). According to the method load of scrap is carried out in a pre-fused flux, heating is carried out by passing an alternating electric current power 7-1 kA per square meter of the surface of the metal at a voltage of 10-20 V, and the smelting of lead under the flux layer thickness of 20-40 cm in the ratio 1:(5-20) by weight of scrap and flux. As a flux, a mixture of salts of alkaline and alkaline-earth metals with a density less than the density of the scrap 0.3-0.5 g/cm³.

Defects in the rigid of this method is the use of electricity in the process and the use of salts, containing fluorine, for dissolution of oxide films on the surface of the waste with a developed surface.

Salt in the form of cryolite and NaF interact with Mg, and its content in the alloy decreases.

Technical problem on which the invention is directed, is the reduction of waste metals, primarily Mg, improving the quality of the metal due to the complete preservation of the original composition, excluding operations for more podshihtovkoj Mg.

The technical effect obtained by the use of the invention is to reduce the loss of active metal in the alloy in 1,5-2 times, excluding operations for more podshihtovkoj Mg and reduce labor costs.

This object is achieved in that in the method of recycling scrap aluminum alloys containing magnesium, including loading scrap in pre-fused flux mass ratio of 1:(5-20), heating up to the melting temperature, melting under a layer of flux and separation of the metal from the flux, according to the invention in use as a flux equinology mixture of the chlorides of potassium and sodium with the addition of magnesium chloride or of magnesium fluoride in the amount of 2.9-52,6% of the total mass flux, and the flux in the melting of the support with a thickness of 5-20 see

Thus as an additive to the flux used magnesium chloride content of 48% of the total mass flux or a mixture of the chlorides of barium and communicated to the I in the amount of 15.6% of the total mass flux, and the content of magnesium and barium in the flux support 1.1-8.6 times greater than the content of magnesium in the alloy.

The melting temperature maintained within the range of 708-904°C, preferably 765-800°C.

When the temperature drops <708°removing Mg falls to 50.8%, while increasing over 904°also reduced by up to 67.7 percent.

By reducing the thickness of the layer of salt is less than 5 cm, it ceases to function as a protective layer, because the chips are immersed in him, not completely.

When the layer thickness of more than 20 cm process productivity falls due to the reduction furnace filled with aluminum.

Example 1. In Lundby crucible with a diameter of 50 mm and a height of 120 mm was loaded salt such as NaCl is 58 g, KCl - 72 g, NaF - 20 g and set in the oven tammana, was heated to 740°C. temperature Measurements were made chromel-alumel thermocouple. In the molten salt in 10 receptions downloaded 235 g chips alloy AB of the following composition (weight%): C - 0,235; Mg Is 0.65; Mn - 0,225; Fe - 0,28; Si - 0,78; Zn - 0,085; Ti - 0,058. The average temperature of the experience 904°C, the melting time 35 minutes

The melt was poured into a graphite mold, separated flux and weighed salts and metal. Drew 213,9 g of metal and of 114.5 g of flux. Extraction of Mg in the alloy was 67.7 percent.

Example 2. In Lundby crucible downloaded 94 g NaCl, 120 g of KCl and 32 g MgF₂(ACC. 38,5-49,2-13.3 wt.%), melted, raised the temperature to 725°and 12 receptions downloaded 300 g of chips of the former staff. The average pace is the atur experience was 765,5° C. the melting Time of 45 minutes, the Crucible was removed, the contents were poured, cooled, and separated the metal from the flux and weighed. Removing the Mg was 98,8%.

Example 3. In alongby the crucible was loaded to 90 g NaCl, 170 g KS1, 30 g l₂and 6 g of MgCl₂, melted, raised the temperature to 760°, downloaded 8 receptions 300 g of chips of the former staff. The average temperature of the experience was 774,7°C. the melting Time of 61 minutes, the Crucible was removed, the contents were poured, cooled, and separated the metal from the flux, weighed, and analyzed. Removing the Mg was 96%.

Example 4. In alongby the crucible has uploaded 190 g of a mixture of 9.0% NaCl, 39,0% KCl, 48,0% MgCl₂, melted, heated to 770°and 8 receptions downloaded 300 g of chips, a piece of metal that came out in the form of goldcrests in the ingot has passed 70% metal, the content of magnesium in the metal 86.2 per cent.

Example 5. Salt from previous experience with the addition of 20 g MgF₂(8,2% NaCl, 35,6% KCl, 43.8% Of MgCl₂, 8.8% of MgF₂) downloaded in alongby the crucible, melted, heated to 775°, downloaded 8 receptions 300 g chip. Average temperature 768,7°C. experience Time 85 minutes Poured into the mold, separated the bar from the flux, weighed, and analyzed the metal, removing the magnesium happened 90,6%.

The results of experiments on the melting chips and other waste containing magnesium, are shown in tables 1, 2, 3.

Table 2 shows that the compositions of the salts containing NaF, allow to extract magnesium tourny alloy is not more than 83% (op. 1-7, 18-1, 19-1). The most promising formulations containing MgF₂(op. 12 and 24) and carnallite, and mixtures thereof. In addition, good results have demonstrated experience with the presence of barium chloride and magnesium fluoride (experiment 16).

The highest extraction of magnesium occurred in the temperature range 765-800°C.

Table 3 shows the chemical composition of the source and obtained after melting of aluminum alloys in laboratory and industrial conditions containing magnesium from 0.65 to 5.78 percent.

Sources of information

1. Kimstach G.M. Preparation of secondary aluminum alloys of chips at machine-building plants. Foundry, 1981, No. 1, p.14-15.

2. Maöan A.G., Resnekov A.A. Melt in saline raw materials containing aluminum and metal inclusions”. The book “Light alloys in the national economy, 1975, str-181.

3. Kazantsev GF, Barbin NM, Kalashnikov, VA Patent RF №2089630 “Method of recycling scrap aluminum alloys”. 30.04.1993,

1. Method of recycling scrap aluminum alloys containing magnesium, including loading scrap in pre-fused flux mass ratio of 1:(5-10), heating up to the melting temperature, melting under a layer of flux and separation of the metal from the flux, characterized in that as a flux used equinology mixture of the chlorides of potassium and sodium with the addition of magnesium chloride or of magnesium fluoride in the amount of 2.9-52,6% of the total mass flux and the flux layer by melting a support with a thickness of 5-20 see

2. The method according to claim 1, characterized in that as an additive to the flux used magnesium chloride content of 48% of the total mass of the flux.

3. The method according to claim 1, characterized in that the additive use magnesium chloride in a mixture with barium chloride with an amount of the mixture of 15.6% of the total mass flux, the content of magnesium and barium in the flux support 1.1-8.6 times greater than the content of magnesium in the alloy.

4. The method according to claim 1, characterized in that the melting temperature maintained within the range of 708-904°C, preferably 765-800°C.