LU82135A1 - PROCESS FOR REDUCING THE CONTENT OF MOLTEN MASS CONTAMINANTS OF ALUMINUM AND ALUMINUM ALLOY - Google Patents

Description

S ~ ft — 3 ~ L GRAND-DUCHY OF LUXEMBOURG L-2483

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of ____________________ filTDlIÿ Minister 1¾¾¾ of the National Economy and the Middle Classes

Title issued: ........................................ -V "" en

LUXEMBOURG Industrial Property Service

Patent Application I. Application

Magyar Aluminumipari Trôszt, 56, Pozsonyi ut, Budapest XIII ... "'Hungary,' .......... ^ axwëïTë'r ',' '2I-'2'5 ..... ^ 2T 'ëe' '' 'Bclie'ffër', '

Luxembourg, acting as agent (2) files this cinema ?. February niil nine hundred and ninety (3) t at ... 15.-, 00 ...... hours, at the Ministry of National Economy and Middle Classes, in Luxembourg: 1. this request for the '' obtaining a patent for an invention concerning: ....................................... .................................................. .................................................. .................................................. ............................................-..... ....................................... (4)

Process for ..... reducing the content of ..... mass contaminants ............................... ....

aluminum and aluminum alloy fondue. - declares, assuming responsibility for this declaration, that the inventor (s) is (are): _______________________ (5) 30, Kofém I.tp., Székesfehirvar, Hungary - Laszlo Jekisa, 15, Hosszuséta-têr, ' Szekesfehervar '^ 27, Kof ëiTT.tp. ^

Mihaly Stein, 22, Kofém I.tp., Szëkesfehérvar »Hungary - Ferenc Szabo, 37, Kofém IJL

.................................................. ................ '□' ΤΙΓ ^ ΙΓΓ ............................ ...

2. the delegation of power, dated ........ 9 “&. Epesu____________________________ on ..... ^ çj -January lSSO

3. description in French ................. language ......................... of the invention in two copies; 4 ............ 4 ................. drawing boards, in two copies; 5. the receipt of the taxes paid to the Luxembourg Registration Office on .......... 9.i.nâ ..... February ... mil ..... new .. ... ce.nt .... qUatr.C.-vln.gt _________________________________________________________________________________________ claims for the above patent application the priority of one (s) application (s) of (6) ....... .patent................................................ ............ filed® in (7) -----------------. Hungary ------------- ---------------------------------------------------------- - on .............. eight ..... February ... ^ ..... s „Qixa.nt. £ ..... dixrn £ .uf ..... under .... on ..... no .......... (8) 4 MA-3106 in the name of Magyar Aluminiumipari Troszt .......... .................................................. ................................. (9) elect domicile for him / her and, if designated, for his / her agent, in Luxembourg _____________________________ ••• ι1 · θ & 'η ···· ΐιϊ3 · χ · ν7' © · ΐ-1 · 0 ·: Ε''7 ·· 2 "1—2'5 ··· Alley. .... Se'fre'ff'eryljUX'eiïïbourg ---------------------------------- ---------------------- h®) requests the issuance of an invention patent for the subject described and represented in the abovementioned appendices, - with adjournment from this issue to .................. L .......................... month .

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Π. Deposit Minutes

The above application for a patent for invention has been filed with the Ministry of National Economy and Middle Classes, Industrial Property Service in Luxembourg, on: 05.02.1qftn / '...... \ Pr. Minister at ....... hours of 1,; ®conornie Nationale #t dgs Classes Moyennes, ïwl

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CLAIM OF PRIORITY

Filing of the patent application in Hungary from February 8, 197 9 to US number MA-3106

DESCRIPTIVE MEMORY FILED IN SUPPORT OF A PATENT INVENTION APPLICATION

. IN THE GRAND DUCHY OF LUXEMBOURG

MAGYAR ALUMINUMIPARI TRÖSZT

by;

for; PROCESS FOR REDUCING THE CONTENT OF

MASS CONTAMINANTS OF ALUMINUM AND ALUMINUM ALLOY.

T

PROCESS FOR REDUCING THE CONTENT OF MOLTEN MASS CONTAMINANTS OF ALUMINUM AND ALUMINUM ALLOY

The present invention relates to a method for reducing the content of contaminants present in aluminum or aluminum alloy melts; more particularly, the content of alkali metal, of gaseous hydrogen and of non-metallic solid contaminants, such as oxide, can be reduced by introducing aluminum or aluminum alloy isolated from the air into the melt. and maintained at a temperature between 670 and 860 ° C, an inert gas under a pressure of less than 2 atmospheres, preferably nitrogen gas, containing a powder capable of giving off chlorine gas.

Various processes are known for purifying metals. Among these methods, the most effective are carried out using an active gas, such as chlorine or salts capable of releasing chlorine gas, such as halides.

A rinse is carried out using chlorine gas (Tomany, J.P.:

The control of aluminum chloride fumes - Light metal age, 1968. 26. n ° 9-10. p. 19-20)

The content of hydrogen gas, oxide and alkali metal of most alloys can be reduced, but at the same time most of the gas (introduced into the melt through pipe, graphite or steel, coated with a resistant coating) does not participate in the purification process and causes serious problems of neutralization and absorption. In the workshops of factories that use chlorine gas, iron structures are exposed to. 30 corrosion, and during the handling, storage and neutralization of this chlorine, the risk of poisoning is continuous (Nolting, P.: Betriebliche Erfahrungen mit der Chlorbehandlung von Aluminumlegierungen. Tiiesserei. 61. 1974. n ° 1 p. 7-10).

2

This problem can be solved by injecting, for rinsing, a gaseous mixture of chlorine and nitrogen or one of the noble gases such as argon, helium, neon, krypton, xenon, used alone or in mixture.

5 Nitrogen is a gas which does not react with aluminum.

Generally, gas mixtures of chlorine and nitrogen are used having the following composition: - 10 to 35% by volume of chlorine gas and 10 - 55 to 90% by volume of nitrogen gas i The ability to remove hydrogen gas in this gas mixture is less than that of pure chlorine but greater than that of pure nitrogen (Presche. P. Wulmstrof. n.: Behandlung von Aluminiumschmelzen mit Gasgemischen. Aluminum 48. 1972. N ° 10. p. 677 -678).

15 Among the gases inert towards aluminum, there may be mentioned argon which reduces the hydrogen content of the melt in a more efficient way than nitrogen (Ginsberg H. - Agrawal AN: Überprüfung der Wirkungsweise gebräuchlicher Entgasungsmethoden für Metallschmelzen aus Reinaluminium und Aluminum-Magnesium-Legierungen unter Anwendung der neuen 20 Qasbestimmungsapparaturen. III. Aluminum 41. 1965. No. 11. p. 683-687).

In addition, argon and the other noble gases are rather expensive and their use has not been introduced in the aluminum industry.

By liquefying and separating the air, large quantities of nitrogen can be produced economically. However, by carrying out the rinsing with nitrogen, it is obtained that a low degree of degasification in the case of the alloys of alloyed aluminum and at the same time, a surface formation of the metal is formed. slag difficult to treat and containing a relatively high amount of metals, which increases the loss of metal.

The nitrogen also does not decrease the alkali metal content of the melt, so nitrogen alone is not suitable for purifying melt contaminated with alkali metals, and it should only be used after mixing. with chlorine. (Székely A.G.: The Remo-val of solid particles from molten aluminum in the spinning nozzle inert 35 flotation process. Metallurgical transactions 7B. 1976. p. 259-270).

To reduce the sodium content, the most effective is to use chlorine - (Lagowski. B.: Magnesium Loss during chlorination of aluminum 3 melts. The plains III. Trans. Amer. Foundrymen's Soc. 77. 1969. p. 206 -207), in the gaseous state.

By introducing chlorine gas into the melt, Al Cl 2 is formed so that the sodium is bound: 5 A1C13 + Na + 3 NaCl + Al

NaCl + Al Cl 3 - * · (AlCl3, NaCl) +

Among the salts capable of generating a gas, chlorides such as, for example, manganese or zinc chloride, react with liquid aluminum and thus form aluminum chloride, which is then found in the state gaseous at processing temperature. (Marienbakh. L.M. Sokolovskii. L.O.: Plavka slavov tsvetnykh metallov dlya fasonnogo litya. Moscow. 1967. p. 184-189).

3 MeCl2 + 2 Al · * · 2 A1C13 + 3 Fie

Alurninium chloride in the gaseous state also reduces sodium contamination of the melt.

Hexachloroethane is also used to reduce the contaminant content in aluminum or aluminum alloy melts, (Marienbakh. LM - Sokolovskii. LO: Plavka slavov tsvetnykh metallov dlya fasonnogo litya. Moscow 1967. p. 184-189 ).

20

The reaction of hexachloroethane in the aluminum melt is as follows: 3 C2Clg + 3 C2C14 + 3 Cl2 2 Al + 3 Cl2 ^ 2 A1C13 25 3 C0C1, + 2 Al 3 C.X1- + 2 A1C1 „LO c 4 o

Given the violence of the reactions taking place and the risk of explosion, the quantity of treatment material required to obtain the desired effect cannot be added at once to the liquid metal. Such processes are known in which Thexachloroethane 30 is added in small amounts to the melt. This means additional costs and at the same time the powder packaged in sheets or capsules or the compact compressed tablets must be introduced into the melt with the aid of an immersion bell at the cost of a laborious manual operation which cannot be mechanized.

In the case of furnaces with a large bath surface, the supply cannot be uniform so that the degree of use of hexachloroethane is low and that a large portion of this material is practically unused and lost with waste gases.

A vacuum treatment is also applied to carry out the purification of the liquid metal. (Alker, K.: Aluminumentgasen im Vakuum. Vakuumbehandlung betriebssicher und umweltfreundlicher als Chlorierungs-verfahren. VDI-Nachrichten 27. 1973. N ° 22. p. 12).

The disadvantage of this process is that only the upper part of the melt is degassed. (Makarov. G.S.: Zakonomernosti udaleni-ya vodoroda pri vakuumnoi obrabotke rasplavlennogo alyuminiya. Tekln.

Legk. Splavov. 1970 n ° 4. p. 37-42).

The process is expensive because the construction and operation of a vacuum furnace requires significant investment and maintenance costs.

Ultrasonic treatment also belongs to known methods for reducing the hydrogen content. (Livanov, V.A. et al.: Rafinirovaniye alyuminiya i ego splavov ul'trazvukovymi kelebaniyami. Tsvetnye Métally. 1968. N ° 6. p. 82-84).

This process has not been applied on an industrial scale.

The physical methods have a disadvantage, such as that they do not reduce the alkali metal content of the aluminum melt.

In the past 15 years, the equipment for carrying out the treatment of metals in a continuous operation outside the furnace has undergone significant development.

These equipments are described below.

The equipment bearing the trade name FILD of the firm Gautschi combines nitrogen rinsing with filtration through 30 activated alumina beads. (Entgasung und Reinigung von Aluminiumschmelzen. Gautsch folder. Aluminum 50. 1974. N ° 4 p. 297).

BASF uses continuous equipment based on petroleum coke. This equipment combines rinsing with neutral gases and filtration through a mechanical surfactant filter bed. (Böhm G; 35 “Das Filtrieren und Entgasen von Alumini umschmelzen im Durch! Aufverfahren. Aluminum. 1973. N ° 11. p. 743-747).

In the equipment produced by the company Carborundum, the main filter element is an attached filter composed of porous tubes with the trade name Aloxit.

This added filter is located in a filtering system provided with upper electric heating, so that the metal penetrates through the envelope of the tubes and collects in a collector, under the effect of metallostatic pressure. (Mahesh, C. Mangalick: The rigid media filter - principles and applications. Manuscript presented on the 102 nd annual mesting of the AIME. Chicago. 1972).

"

Union Carbide Corporation implements a flotation process in place of the filtration process to achieve separation of solid contaminants using SNIF equipment. (Székely A.G.: The Removal of solid particles from molten aluminum in the spinning nozzle inert flotation process. Métal 1urgical transactions 7B.

1976. p. 259-270), 15 The equipment used by the firm Alcoa contains two filter beds through which a mixture of chlorine and argon gas is passed. (Blayden, L.C. - Brondyke, K.J.: Alcoa 469. Process.

Low cost, non-polluting, continuous metal fluxing. Journal of metal s.

1974. February - p. 25-28).

All these methods are advantageous, in continuous foundries, in which the casting period is long and the non-scouring treatment in the furnace is not sufficient to keep the hydrogen gas content of the feed at the low required value. until the end of the casting. However, these methods have a common disadvantage in that the gaseous reaction products, given their relatively high throughput (3 to 20 tonnes / hour), and the short residence times, cannot be carried completely up to on the surface. To compensate for this drawback, reactors having several chambers have been developed, but the dimensions and the heating system thereof are similar to those of furnaces and thus they can hardly be adapted between the existing foundry and the furnace.

The object of the invention is to eliminate the above drawbacks and to develop a continuous process for reducing the contaminant content of the molten masses of aluminum and aluminum alloy; by carrying out this process, the treatment material can be used more and the purification process can be carried out in a regular and controllable manner.

It was surprisingly found that by introducing into the molten mass 6 of aluminum or aluminum alloy, isolated from the air, a powder which generates chlorine gas, conveniently zinc or magnesium chloride, hexachloroethane or manganese chloride, mixed with an inert gas such as nitrogen *, the quantity of powder generating chlorine gas, necessary to remove a certain quantity of contaminant, can be reduced in the process according to the invention, d about 60% compared to the methods known in the prior art.

The advantages of the process according to the invention can be summarized as follows: 1 1 - using the process according to the invention, the quantity of powder, releasing chlorine gas, necessary for the elimination of a given quantity of contaminant, is greatly reduced; that is, the treatment material is used more and the amount of this unused material is reduced. From an economic point of view, this fact is of absolutely priceless importance.

2 - the method according to the invention can be carried out continuously and controlled automatically with great precision. The purification process can therefore be carried out, at the cost of less physical energy, in a well controllable manner.

3 - the purification carried out, in the absence of air, so that any other contamination by oxides can be eliminated. In fact, other contaminants of the oxide type can form, in the presence of oxygen from the air.

4 - another advantage of the process according to the invention lies in the fact that by applying this process, the aluminum content of the slag, formed during the treatment, is much lower than that observed by carrying out a treatment. in the presence of nitrogen only.

The method according to the invention is carried out in an equipment shown diagrammatically in FIG. 1.

The pressurized container (1) of FIG. 1 can be filled with treatment material after opening the cover (9). The supply device (4) conveys the treatment substance into the mixing zone (5). The feed speed can be varied in stages, and is stabilized with the aid of the control unit (3) with great precision. The filling of the container containing the treatment substance is controlled by a signal induced by the system (2).

The support gas enters the mixing zone (5) via the pressure regulator and the stabilizer (7). The volume of the gas can be controlled by a flow meter (6).

The mixture of the gas and the treatment substance prepared in the mixing zone flows through the flexible tube (8) into the treatment pipe (10). The latter is made from a material resistant to the effect of liquid metal.

The purification of the metal using a mixture of gas and treatment substance is carried out under industrial conditions for the treatment of aluminum and aluminum alloy melts.

The treatment substance is Thexachloroethane while the carrier gas is nitrogen.

The process according to the invention is further illustrated with the aid of the following nonlimiting examples:

EXAMPLE 1 A melt of aluminum-magnesium-silicon alloy is treated in a reverberatory furnace of the 15-tonne tank type using equipment, as shown in FIG. 1.

The flow rate by volume of the support nitrogen used for the treatment is 0.4 to 0.5 Nm3 / minute. The treatment is started at a temperature of 710 - 720 ° C.

In half of the cases, no salt releasing chlorine is added to the nitrogen. The quantity of hexachloroethane used is 2 kg / tonne of melt (0.2%).

The gas content of the molten mass before and after treatment is indicated in Table 1. The gas content is determined by the "first bubble" method. Nitrogen is capable of removing 9 to 33% of the hydrogen gas present in the melt.

By adding thexachloroethane to nitrogen as an agent capable of releasing chlorine, the content of hydrogen can be reduced from 48 to 77%.

The slag formed is dry, powdery, its aluminum content is low; when a treatment is carried out in the presence of nitrogen alone, a soft slag forms. Upon addition of the hexachloroethane, the temperature of the melt does not decrease due to the heat of reaction given off during processing. By carrying out the treatment with nitrogen alone, the temperature decreases by 15 ° C.

Example 2

An aluminum-magnesium-silicon alloy melt is treated in the equipment shown in FIG. 1, in a tank-type reverberatory furnace, the reaction conditions being as indicated in Example 1. The pulverulent hexachloroethane serves as a salt capable of generating chlorine gas.

5 By way of comparison, in another test, hexachloroethane pellets are introduced into the melt, according to the method of the immersion bell.

The quantity of treatment substance is in both cases equal to 2 Kg / tonne of melt.

10 The content of hydrogen gas is shown in Table 2.

When a stream of nitrogen is introduced, the reaction conditions are better and the gas content of the melt decreases by 58 to 70%, that is to say that one obtains a purification effect twice as much higher than when using 15-hexachloroethane tablets.

The same effect is observed on the oxygen content of the melt. While the oxygen concentration of the melt is 10 ppm with powdered hexachloroethane. This value is approximately 18 ppm with the pellets. The variation in the oxygen content in the case of treatment with hexachloroethane tablets or with powdered Thexachloroethane supplemented with nitrogen is shown in Tables 6 and 7.

Example 3

The reduction in the hydrogen content in a melt of aluminum-magnesium-silicon alloy is studied as a function of the quantity of powdered hexachloroethane introduced as a chlorine-generating agent, using the equipment of the type of figure 1.

Figures 2 and 3 show the efficiency of the purification carried out in 15-ton furnaces in the presence of pellets of hexa-30 chloroethane and hexachloroethane powder introduced with nitrogen.

In FIG. 2, the hydrogen content of the melt (in ml / 100g) is indicated as a function of the specific consumption of hexachloroethane (in Kg / ton of melt).

In FIG. 3, the initial hydrogen content is indicated (denoted Sk and given in ml / 100g) as a function of the specific consumption of hexachloroethane (given in Kg / tonne of melt). The hydrogen contents are also provided at the end of the treatment (called Sv). The solid lines refer to a treatment with powdered hexachloroethane in combination with nitrogen while the dashed lines refer to a treatment carried out with hexachloroethane pellets. The effectiveness of powdered hexachloroethane introduced into a stream of nitrogen exceeds that of treatment with 5 tablets of hexachloroethane. This is shown in Figure 3 for an initial hydrogen content of 0.3 ml / 100g and a final hydrogen content of 0.1 ml / 100g.

To obtain the same purification, the reduction in the consumption of hexachloroethane can reach 60%.

10 By injecting powdered Thexachloroethane into a stream * of nitrogen, the oxygen content decreases to 5 ppm in the case studied.

Example 4 Using the equipment indicated in FIG. 1, a charge of 13 tonnes of aluminum-magnesium-15 silicon alloy melt is treated in a reverberatory furnace of the tank type.

The changes in the sodium content appearing as a result of the injection of a quantity of 2 kg / tonne of molten mass, hexachloroethane powder producing chlorine, are noted.

In Table 3, the sodium contents determined before and after the treatment are compared. The decrease is from 27 to 65%.

The efficiency of the purification which can be obtained by increasing the quantity of hexachloroethane powder applied is shown in FIG. 4 in which the sodium content (ppm Na) is indicated as a function of the consumption of hexachloroethane (Kg / 25 tonnes of melt).

Example S

Using the equipment of the type indicated in FIG. 1, a molten mass of aluminum-magnesium-silicon alloy is treated in a reverberatory furnace of the 15-tonne tank type.

The nitrogen flow rate used for the treatment is 0.4 to 0.5 Nm 3 / minute. The treatment temperature is 710 to 720 ° C.

Table 4 shows the oxygen content of the melt before and after the nitrogen treatment. The oxygen content is determined by the neutron activation method. On average, no decrease in oxygen content is observed. On the contrary, this oxygen content increases even in the majority of cases.

Example 6

In a reverberatory furnace, a load of 25 tonnes of aluminum-magnesium-silicon alloy melt is treated with hexachloroethane pellets. The changes in sodium content are noted after mixing chlorine-releasing hexachloroethane pellets, at a rate of 2 kg / tonne of melt.

5 The treatment temperature is 710 to 720 ° C.

The sodium contents before and after the treatment are provided in Table 5 for comparison.

The sodium content decreases from 14 to 57%.

TABLE 1 10

GAS HYDROGEN CONTENT

Treatment with N2 Treatment with ^ 2 + C2 ^ 16 before after before after 15 ...... decrease decrease treatment treatment ml / 100 g ml / 100 g ml / 100 g ml / 100 g 0 /

Al Al% Al Al 0.23 0.21 9 0.20 0.09 55 20 0.11 0.08 27 0.26 0.10 62 0.21 0.14 33 0.21 0.06 71 0, 27 0.24 U 0.23 0.12 48 0.24 0.17 29 0.22 0.05 77 25 TABLE 2 *

GAS HYDROGEN CONTENT

Treatment with tablets Treatment with N2 + C2C16 C ^ Clg in Poudr® 30 before I after | before after . .. ', decrease decrease _treatment t _treatly_ ml / 100 g ml / 100g ml / 100 g I ml / 100 g 0/0 /

Al Al h Al Al h 0.19 0.16 16 0.20 0.06 70 35 0.22 0.19 14 0.32 0.11 66 0.32 0.23 '28 0.23 0.09 61 0.21 0.19 10 0.26 0.10 62 0.32 0.25 22 0.24 0.10 58 TABLE 3 11

SODIUM CONTENT

Treatment with N ^ + 2 Kg / t C ^ Clg powder 5 before treatment after treatment decrease ppm ppm% 15 11 27 6 4 33 20 7 65 10 10 7 30 7 4 43 TABLE 4

15 OXYGEN CONTENT

Treatment with N2 gas before treatment after treatment change ppm ppm 20 30 40 +10 30 65 +35 25 38 +13 25 43 +18 38 30 - 8. 25 40 35 - 5 38 40 +2 25 30 +5 40 35 - 5 30 30 0 ._î 12 TABLE 5

SODIUM CONTENT

Treatment with 2 Kg / t of pellets of C ^ Clg 5 --- d-- before treatment after treatment decrease p pin ppm% 8 5 # 37.0 5 3 40.0 10 7 4 43.0 8 5 37.0 7 3 57.0 6 4 33.0 9 6 33.0 15 7 6 14.0 10 8 20.0 TABLE 6 20

OXYGEN CONTENT

Treatment with C2C16 tablets * 25 before treatment after treatment decrease ppm ppm% 30 25 17 55 45 18 30 35 30 14 40 35 13 45 35 22 TABLE 7

K

13

5 OXYGEN CONTENT

Treatment with + C ^ Clg powder before treatment after treatment · decrease 10 ppm ppm% 35 20 43 30 20 33 25 15 40 15 25 20 20 30 25 17

Claims (4)

1. Method for reducing the contaminant content of molten aluminum or aluminum alloys, making it possible mainly to reduce the content of alkali metal, hydrogen and non-metallic solid contaminants - 5 Ticks, such as oxides, characterized in that an inert gas is introduced into the molten mass of aluminum or aluminum alloy isolated from the air and brought to a temperature of 670 to 860 ° C. pressure less than 2 atmospheres, preferably nitrogen, containing a powder which gives off chlorine gas. 10 2. Method according to claim 1 characterized in that zinc chloride, magnesium chloride, or manganese chloride or hexachloroethane is used as a powder releasing chlorine. 3. Method according to claim 1 or 2 characterized in that ^ one uses hexachloroethane as a powder which releases chlorine. 4. Method according to claim 1 to 3 characterized in that Ton uses powder which gives off chlorine at a rate of 0.05 to 10 Kg / ton of molten aluminum or aluminum alloy.