RU2244027C1 - Method for reprocessing of junks of magnesium containing based-based alloys - Google Patents

Abstract

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

Description

The invention relates to ferrous metallurgy, in particular to methods for processing aluminum waste.

There is a method of melting ALCH alloy in induction furnaces IAT-2.5 (Kimstach G.M. Preparation of secondary aluminum alloys from shavings at engineering plants. Foundry, 1981, No. 1, pp. 14-15).

The flux consumption in this case is 2 - 2.5%. Good results are provided by a flux of 47% KCl, 30% NaCl, 23% Na ₃ AlF ₆ . The metal burn during melting is ~ 22%.

To improve quality at 740 ° C, the crucible walls are cleaned of flux, slag is removed from the furnace, and 1.5% of flux is fed to the surface of the bath. After melting the flux, the melt is treated with hexachloroethanol, which is introduced at 0.1% by weight of the heat with a total flow rate of 0.7-0.8%.

The specified method does not ensure the conservation of Mg in the melt, since it interacts with cryolite and is removed from the melt. In addition, the use of volatile hexachloroethanol worsens environmental conditions during the smelting of chips. A small amount of refining flux is mixed with oxides and, at the end of smelting, the flux is completely removed from the metal surface, i.e. This is a disposable flux.

A known method of reflow in a salt solution of raw materials containing aluminum and metal inclusions. The raw materials were scrap and waste of aluminum alloys of the AL 34 and AL 104 grades (Mashan A.G., Reznyakov A.A. Reflow in a saline solution of raw materials containing aluminum and metal inclusions. Collection “Light alloys in the national economy”, 1975, pg. 176-181).

When melting in “light” fluxes, i.e. with a specific gravity less than that of aluminum, the highest degree of aluminum recovery (98%) is achieved at 780-800 ° C using fluorspar.

The flux consumption in this case is: for the composition KCl + NaCl + cryolite - 0.5 kg / kg of the charge, and for the composition KCl + NaCl + CaF ₂ - 0.28 kg / kg of the charge. In the first case, the reflow rate is 27 g / min, in the second - 34 g / min.

The disadvantage of the method is the same as in the previous case, cryolite interacts with magnesium and impoverishes its alloy. In addition, a large consumption of fluxes is required.

The closest in technical essence is the method of processing scrap aluminum alloys (RF patent No. 2089630, application. 04/30/93, publ. 09/10/97, BI No. 25, 1997, p.271). According to the known method, the scrap is loaded into a pre-molten flux, heating is performed by passing an alternating electric current of 7-1 kA per square meter of metal surface at a voltage of 10-20 V, and melting is carried out under a flux layer with a thickness of 20-40 cm at a ratio of 1: (5-20) by weight of scrap and flux. As a flux, a mixture of alkali and alkaline earth metal salts with a density lower than the scrap density by 0.3-0.5 g / cm ^{3 is used} .

The disadvantage of this method is the use of electricity in the process and the use of salts containing fluorine to dissolve oxide films on the surface of waste with a developed surface.

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

The technical problem to which the invention is directed is to reduce the burning of metals, primarily Mg, to improve the quality of the metal due to the complete preservation of the initial composition, to exclude the operation of additional grinding of Mg.

The technical effect obtained by using the invention is to reduce the loss of active metal in the alloy by 1.5-2 times, eliminating the operation of additional underlining of Mg and reducing labor costs.

The problem is achieved in that in a method for processing scrap aluminum alloys containing magnesium, comprising loading the scrap into a pre-molten flux in a mass ratio of 1: (5-20), heating to the melting temperature, melting under a flux layer and separating the metal from the flux, according to According to the invention, an equimolar mixture of potassium and sodium chlorides with the addition of magnesium chloride or magnesium fluoride in the amount of 2.9-52.6% of the total mass of the flux is used as the flux, and the melting flux layer is maintained at a thickness of 5-20 cm.

In this case, magnesium chloride with a content of 48% of the total mass of the flux or a mixture of barium and magnesium chlorides in the amount of 15.6% of the total mass of the flux is used as an additive to the flux, and the content of magnesium and barium in the flux is maintained at 1.1-8, 6 times more than the magnesium content in the alloy.

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

With a decrease in temperature <708 ° C, the extraction of Mg drops to 50.8%, and with an increase over 904 ° C it also decreases to 67.7%.

With a decrease in the thickness of the salt layer less than 5 cm, it ceases to work as a protective layer, because the chips are not completely immersed in it.

With a layer thickness of more than 20 cm, the productivity of the process decreases due to a decrease in the volume of the furnace filled with aluminum.

Example 1. In the alundum crucible with a diameter of 50 mm and a height of 120 mm, salts were loaded: NaCl - 58 g, KCl - 72 g, NaF - 20 g and installed in a Tamman furnace, heated to 740 ° C. Measurement of temperature was carried out with a chromel-alumel thermocouple. 235 g of chips of alloy AB of the following composition (wt.%) Were loaded into the molten salt in 10 stages: Cu - 0.235; Mg 0.65; Mn 0.225; Fe 0.28; Si 0.78; Zn - 0.085; Ti - 0.058. The average temperature of the experiment 904 ° C, the melting time of 35 minutes

The melt was poured into a graphite mold, the flux was separated and the salts and metal were weighed. 213.9 g of metal and 114.5 g of flux were recovered. Extraction of Mg in the alloy was 67.7%.

Example 2. In an alundum crucible, 94 g of NaCl, 120 g of KCl and 32 g of MgF ₂ (resp. 38.5-49.2-13.3 wt.%) Were loaded, melted, the temperature was raised to 725 ° C and in 12 doses loaded 300 g of chips of the previous composition. The average temperature of the experiment was 765.5 ° C. Melting time 45 minutes The crucible was removed, the contents were poured, cooled, the metal was separated from the flux and weighed. The Mg recovery was 98.8%.

Example 3. In an alundum crucible, 90 g of NaCl, 170 g of KCl, 30 g of BaCl ₂ and 6 g of MgCl _{2 were} loaded, melted, the temperature was raised to 760 ° C, and 300 g of the old chip was loaded in 8 doses. The average temperature of the experiment was 774.7 ° C. Melting time 61 minutes The crucible was removed, the contents were poured, cooled, the metal was separated from the flux, weighed, analyzed. The Mg recovery was 96%.

Example 4. 190 g of a mixture of 9.0% NaCl, 39.0% KCl, 48.0% MgCl _{2 was} loaded into an alundum crucible, melted, heated to 770 ° С and 300 g of chips were loaded in 8 steps, part of the metal turned out Kings, 70% of the metal was transferred to the ingot, the magnesium content in the metal was 86.2%.

Example 5. Salts from a previous experiment with the addition of 20 g of MgF ₂ (8.2% NaCl, 35.6% KCl, 43.8% MgCl ₂ , 8.8% MgF ₂ ) were loaded into an alundum crucible, melted, heated to 775 ° C, loaded into 8 doses of 300 g of chip. The average temperature is 768.7 ° C. The experiment time is 85 minutes It was poured into the mold, the ingot was separated from the flux, the metal was weighed and analyzed, magnesium extraction was 90.6%.

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

Table 2 shows that the salt compositions containing NaF allow magnesium to be extracted into the salable alloy by no more than 83% (op. 1-7, 18-1, 19-1). The most promising compositions containing MgF ₂ (op. 12 and 24) and carnallite, as well as mixtures thereof. In addition, a good result was shown by an experiment 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 initial and obtained after remelting aluminum alloys in laboratory and industrial conditions, containing magnesium from 0.65 to 5.78%.

Table 1.
Smelting conditions for chips containing magnesium. No. t ° C τ time Salt consumption Metal consumption Extraction Extraction experience swimming trunks, min. Loading., G. It is poured, g. Losses % loss Loading., G. It is poured, g. Losses % loss all metals,% magnesium from the loaded,% 2 904 35 150 114.5 35.5 23.7 235 213.9 21.1 8.9 91.0 67.7 3 708 28 180 127.2 62.8 34.9 360 291 69 19.16 80.8 50.8 4 837.9 58 177.2 167.1 10,2 5.7 400 432.5 +32.5 +8.12 95.2 78.5 5 846.3 52 252 250 2 0.8 300 287 thirteen 4.3 95.7 70.8 6 831.2 49 250 203 47 18.8 300 288.6 11,4 3.8 96.2 72.8 7 818.2 58 214.4 160 54,4 25,4 300 283.2 16.8 5,4 94.6 83.1 10 744.1 110 165 148 17 10.3 300 282 eighteen 6 94.0 61.0 12 765.5 45 244 158 86 35,2 300 282 eighteen 6 94.0 98.8 14 771.7 70 230 223 7 3.04 300 261 39 12.9 87.1 81.2 fifteen 774.8 60 163 159.7 3.3 2.02 300 276.3 23.7 7.9 92.1 81.4 16 774.9 61 203 176 27 13.3 300 296.0 4.0 1.3 98.7 96.0 +27 s 19 769.2 28 180 207 box +15.0 300 211.5 88.5 29.5 70.5 86.2 met. 23 768.7 85 227 153 74 32,5 300 332.5 +32 +10.8 110.8 90.6 24 800 60 405 380 25 6.17 600 595 5 0.85 99.15 99.15

Table 2.
Dependence of metal recovery on salt composition. No. The composition of the salts in wt.% Ex. Mg% Ex. Al% experience NaCl KCl NaF BaCl ₂ MgCl ₂ MgF ₂ ∑ 1 37,4 47.6 15.0 - - - 100 95.65 2 38.7 48.0 13.3 - - - 100 67.7 91.1 3 37.3 47.7 15.0 - - - 100 50.8 80.8 4 39.2 50,0 10.8 - - - 100 78.5 98.12 5 37.3 47.6 15.1 - - - 100 70.8 95.7 6 37.3 47.6 15.1 - - - 100 72.3 96.2 7 37.3 47.6 15.1 - - - 100 83.3 94.6 8 44,4 55.6 - - - - 100 - 7.7 10 37.3 47.6 15,2 - - - 100 61 95.5 12 38.5 49.2 - - - 13.3 100 98.8 94 14 39.1 47.8 - 13.1 - - 100 81.2 87 fifteen 39.1 47.8 - 13.1 - - 100 81.4 92.1 16 37.9 46.48 - 12.7 - 2.9 100 96 98.66 19 9.0 39.0 - - 48.0 - 96 86.2 70.5 23 8.2 35.6 - - 43.8 8.8 96.4 90.6 99.8 19-1 37,4 47.6 15.0 - - - 100 80.5 95.9 18-1 37,4 47.6 15.0 - - - 100 76.5 94.5 24 37.9 46.8 - - - 15.3 100 99.15 99.15

Table 3.
The chemical composition of the feedstock and the resulting alloys. No. Salt composition The chemical composition in mass percent (Al the rest) experience Cu Mg Mn Fe Si Zn Ti Cr % extracted Mg Chip feedstock Alloy AB 0.235 0.65 0.225 0.28 0.78 0,085 0.058 0.010 Alloy D 16 4.25 1.33 0.38 0.39 0.10 0,090 0.1 - AMG alloy - 5.89 0.62 0.40 0.40 0.20 0,07 - The resulting alloys 2 Alloy AB 0.27 0.440 0.237 0.29 0.69 0,095 0.051 0.008 67.7 3 Alloy AB 0.24 0.330 0.241 0.29 0.55 0,084 0,068 0.009 50.8 4 Alloy AB 0.28 0.510 0.245 0.32 0.71 0,100 0,082 0.009 78.5 5 Alloy AB 0.25 0.460 0.240 0.23 0.63 0,064 0,060 0.010 70.8 b Alloy AB 0.24 0.470 0.239 0.24 0.55 0,084 0,062 0.010 72.3 7 Alloy AB 0.28 0.540 0.222 0.37 0.55 0.116 0,064 0.008 83.1 10 Alloy AB 0.28 0.397 0.240 0.386 0.51 0,088 0,070 0.009 61.1 12 Alloy AB 0.28 0.642 0.217 0.274 0.54 0,088 0,069 0.009 98.8 14 Alloy AB 0.29 0.528 0.214 0.329 0.59 0,088 0,067 0.011 81.2 fifteen Alloy AB 0.29 0.530 0.211 0.410 0.58 0,087 0,068 0.007 81.4 16 Alloy AB 0.29 0.624 0.216 0,305 0.58 0,088 0,072 0.011 96.0 19 Alloy AB 0.29 0.560 0.221 0.343 0.58 0,071 0,070 0.012 86.2 23 Alloy AB 0.33 0.589 0.224 0.499 0.68 0.181 0.058 0.009 90.6 25 Alloy D 16 4.24 1,302 0.370 0.401 0.09 0,040 0.11 - 97.9 thirty AMG alloy - 5.78 0.63 0.42 0.38 0.18 0.06 - 98.1

Sources of information

1. Kimstach G.M. Preparation of secondary aluminum alloys from shavings at engineering plants. Foundry, 1981, No. 1, pp. 14-15.

2. Mashan A.G., Reznyakov A.A. Salt fusion of raw materials containing aluminum and metallic inclusions. ” Collection “Light alloys in the national economy, 1975, pp. 176-181.

3. Kazantsev G.F., Barbin N.M., Kalashnikov V.A. RF patent No. 2089630 “Method for processing scrap aluminum alloys”. 04/30/1993

Claims (4)

1. A method of processing scrap aluminum alloys containing magnesium, comprising loading the scrap into a pre-molten flux in a mass ratio of 1: (5-10), heating to the melting temperature, melting under a flux layer and separating the metal from the flux, characterized in that as fluxes use an equimolar mixture of potassium and sodium chlorides with the addition of magnesium chloride or magnesium fluoride in the amount of 2.9-52.6% of the total mass of the flux and the flux layer during melting is supported with a thickness of 5-20 cm. 2. The method according to claim 1, characterized in that magnesium chloride is used as an additive to the flux with a content of 48% of the total mass of the flux. 3. The method according to claim 1, characterized in that the additive is magnesium chloride mixed with barium chloride with a mixture amount of 15.6% of the total mass of flux, while the content of magnesium and barium in the flux is maintained in 1.1-8 6 times more than the magnesium content in the alloy. 4. The method according to claim 1, characterized in that the melting temperature is maintained within the range of 708-904 ° C, preferably 765-800 ° C.