RU2758700C1 - Flux for processing aluminum alloys - Google Patents

Abstract

FIELD: foundry.SUBSTANCE: invention relates to a flux for processing aluminum alloys and is intended for processing aluminum alloys in foundry production. The flux contains a mixture of NaCl, KCl and a fluoride source at a ratio of components in the mixture of, wt. %: NaCl 10-70, KCl 10-45, KAlF4or NaAlF410-80.EFFECT: invention provides an increase in the efficiency of the flux, the degree of refining, and a decrease in the melting point of the flux and the cost of the flux for processing aluminum alloys.1 cl, 2 tbl

Description

The claimed technical solution relates to the field of metallurgy of non-ferrous metals and is intended for the processing of aluminum alloys in foundry.

Known, for example, the composition of the salt flux [1] for melting aluminum scrap (US 6053959, 25.04.2000, [1]), containing, by weight. %: potassium chloride - 47.5%, sodium chloride - 47.5%, fluoride source (MAlF ₄ , M ₃ AlF ₆ , MF, CaF ₂ ) - 5%, where KAlF ₄ can be a fluoride source.

Also known flux (Altman M. B. "Metallurgy of foundry aluminum alloys. M. Metallurgy", 1972, A. V. Kurdyumov, M. V. Pikunov, V. M. Chursin, E. L. Bibikov "Production of castings from alloys non-ferrous metals ". M. MISiS, 1996, p. 159, [2]), containing, by weight. %: potassium chloride - 47, sodium chloride - 30, sodium hexafluoroaluminate - 23.

The specified analogue [2] is, by the totality of essential features, the closest analogue of the same purpose to the claimed technical solution, therefore it is adopted as a prototype.

The technical problem to be solved is the need to increase the degree of refining and lower the melting point of the flux. The melting point is one of the most important properties of the flux and must be lower than the operating temperatures for the preparation of aluminum alloys. This is explained by the kinetic laws of the reactions, since most metallurgical reactions are heterogeneous, they proceed at the interface. In the case of a solid flux, this interface (contact surface) is much smaller than in the case of a liquid. For this reason, an increase in the area of contact between the phases (melting of the flux) leads to a greater efficiency of the reaction, the faster the flux melts and interacts with the melt, the better.

The disadvantage of analogue [1] is that the content of KAlF ₄ is 5% - this amount of KAlF _{4 is} not enough for the necessary refining effect in terms of removing non-metallic inclusions and hydrogen.

In the prototype [2], the melting point of sodium hexafluoroaluminate is 1013 ° C, which increases the melting point of the flux. In addition, the known content of potassium chloride of 47% and sodium chloride of 30% increases the cost of the flux, since potassium chloride costs about five times more than sodium chloride.

The technical result provided by the claimed technical solution is to increase the efficiency of the flux for processing aluminum alloys.

Another technical result is a decrease in the melting point of the flux.

The technical result of the claimed technical solution is achieved by the fact that the flux for processing aluminum alloys contains a mixture of NaCl, KCl and a fluoride source. It differs in that the source of fluoride is KAlF ₄ or NaAlF ₄ , while the ratio of the components in the mixture is, wt. %:

NaCl 10 - 70 KCl 10 - 45 KAlF ₄ or NaAlF ₄ 10 - 80.

The above essence is a set of essential features of the claimed technical solution, ensuring the achievement of all the claimed technical results.

In a particular preferred case, the ratio of the components in the mixture is, mass. %:

NaCl 47 KCl thirty KAlF ₄ or NaAlF ₄ 23.

The author of the claimed technical solution has made a prototype of this solution, the tests of which have confirmed the achievement of technical results.

Implementation of the technical solution.

The composition of the proposed flux uses the following ratios of components (wt.%):

NaCl 10 - 70 KCl 10 - 45 KAlF ₄ or NaAlF ₄ 10 - 80.

The ratio of the components in this flux is explained as follows.

The melting point of potassium tetrafluoroaluminate KAlF ₄ is 560 ° C, while the melting point of sodium tetrafluoroaluminate NaAlF ₄ is 720 ° C. In the course of the experiment, it was found that the content of KAlF ₄ or NaAlF ₄ in the amount of 23% is optimal for lowering the melting point of the flux and improving the refining effect in terms of removing non-metallic inclusions and hydrogen, in comparison with analogues.

The obtained melting points of the fluxes are shown in Table 1.

Table 1

Content of components,% Melting point, ° C NaCl KCl KAlF ₄ NaAlF ₄ Na ₃ AlF ₆ 47 thirty 23 - - 622 47 thirty - 23 - 635 thirty 47 - - 23 686 Al metallic 659.5

Table 2 shows the indicators of alloy refining with fluxes.

The efficiency of the flux treatment of the melt was compared with the quality of the starting metal. The presented research results indicate the high efficiency of refining alloys with the declared fluxes when processing the melt with the declared flux - as a result, the degree of hydrogen refining increased 4.82 times, for non-metallic inclusions 11.6 times (compared to samples No. 1 and 4), and the price decreased by about 25% (in comparison with samples No. 2 and 4).

table 2

Flux NaCl - 47.5
KCl - 47.5
KAlF ₄ - 5 NaCl - 30
KCl - 47
Na ₃ AlF ₆ - 23 NaCl - 47
KCl - 30
NaAlF ₄ - 23 NaCl - 47
KCl - 30
KAlF ₄ - 23 NaCl - 47
KCl - 47
NaAlF ₄ - 10 NaCl - 47
KCl - 47
KAlF ₄ - 10 Sample number 1
(analogue 1) 2
(prototype 2) 3 4 5 6 Alloy grade 6063 6063 6063 6063 6063 6063 Hydrogen content to refining cm ^3/100 g 0.27 0.27 0.27 0.28 0.26 0.27 The hydrogen content after refining, ^cm3 / 100g 0.25 0.20 0.20 0.18 0.23 0.23 Hydrogen refining degree,% 7.40 25.92 25.92 35.71 11.53 14.81 Content of inclusions before refining, mm ² / kg (PoDFA) 1.0147 1.0255 1.0183 1.0124 1.0196 1.0279 Content of inclusions after refining, mm ² / kg (PoDFA) 0.9579 0.3912 0.3776 0.3563 0.8124 0.8535 Degree of refining for non-metallic inclusions,% 5.59 61.85 62.92 64.80 20.32 16.96 Slag metal content,% 37.0 32.5 24.8 22.2 26.4 28.9 Slagging, kg / t 5.5 4.5 4.1 4.0 4.3 4.3 Flux consumption for refining, kg / t 1 1 1 1 1 1 Flux consumption for slag processing, kg / kg slag 0.25 0.25 0.25 0.25 0.25 0.25

The implementation of the proposed technical solution is not limited to the above example. When the content of KAlF ₄ or NaAlF _{4 is} more than 50%, the flux can be used as a refining reagent for purifying the melt from alkali and alkaline earth metals according to the reactions:

2KAlF ₄ + Mg = 2KF + 3MgF ₂ + 2Al

2KAlF ₄ + Ca = 2KF + 3CaF ₂ + 2Al

KAlF ₄ + 3Li = KF + 3LiF + Al

KAlF ₄ + 3Na = KF + 3NaF + Al

2NaAlF ₄ + Mg = 2NaF + 3MgF ₂ + 2Al

2NaAlF ₄ + Ca = 2NaF + 3CaF ₂ + 2Al

NaAlF ₄ + 3Li = NaF + 3LiF + Al

The claimed flux is used to reduce the metal content in the slag, slagging and cleaning from non-metallic inclusions and hydrogen. Alloys are prepared in a furnace (mixer) under a layer of molten flux to prevent aluminum oxidation in the furnace (mixer) atmosphere and / or slag is processed at the end of the melt to coalesce molten aluminum in order to maximize metal recovery from the slag and reduce slag formation. For refining the melt from non-metallic inclusions and hydrogen, the flux is kneaded along the entire depth of the bath after removing the slag and given a technological exposure of 20 minutes for the inclusions to float up.

The claimed technical solution is implemented using commercially available materials and has found wide application for melting and refining aluminum alloys.

Claims (4)

1. A flux for processing aluminum alloys, containing a mixture of NaCl, KCl and a source of fluoride, characterized in that the source of fluoride is KAlF ₄ or NaAlF ₄ , while the ratio of the components in the mixture is, wt. %: NaCl 10 - 70 KCl 10 - 45 KAlF ₄ or NaAlF ₄ 10 - 80 2. The flux under item 1, characterized in that the ratio of the components in the mixture is, by weight. %: NaCl 47 KCl thirty KAlF ₄ or NaAlF ₄ 23