Method for removing iron impurities in regenerated aluminum alloy

Abstract

The invention discloses a method for removing iron impurities in regenerated aluminum alloy, and belongs to the field of non-ferrous metal regeneration, recovery and impurity removal. The method comprises the following steps: weighing an iron removal flux (25-45 wt.% of boron-containing potassium fluoride, 20-30 wt.% of sodium chloride and 20-35 wt.% of potassium chloride) according to the mass percentage, stirring, mixing and drying; according to the method, the aluminum scrap is put into the smelting furnace to be smelted, then the iron removal flux and the permanganate catalyst are added into the aluminum scrap melt, stirring and standing are carried out, the aluminum melt with the iron impurity element removed is obtained, the method does not affect the aluminum obtaining rate, meanwhile, the iron content is remarkably reduced, and the method is applied to aluminum ingots obtained through green regeneration smelting of the aluminum scrap and has the beneficial effects that the cost is low; the environment is not damaged and the steps are simple.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal regeneration, recycling and impurity removal, and in particular relates to a method for removing iron impurities in a recycled aluminum alloy. Background Art

[0002] Aluminum is a basic raw material closely related to industrial development and people's lives, and is widely used in all aspects of the national economy. As environmental awareness and circular economy awareness gradually increase, recycled aluminum has received more and more attention from the country. Improving the purity of alloys has become one of the important directions for developing high-performance recycled aluminum alloys. Factors affecting the purity of aluminum alloys include gas, inclusions and impurity elements. Research on the influence of gas and inclusions and their control and removal technology has been relatively mature, and many methods have been industrially applied, which can effectively control and reduce the gas and inclusion content in aluminum alloys. However, there is currently no effective control and removal method for the impurity element iron (Fe). Fe is the impurity element that is most harmful to the performance of aluminum alloys. Most aluminum alloys have strict standards for Fe content. For example, the iron content in aviation alloys 7050, 7055, and 7475 is not allowed to exceed 0.15wt.%; in high-performance automotive aluminum alloys 5474 and 6111, the maximum allowable Fe content is 0.40wt.%. Therefore, to develop high-performance aluminum alloys, it is necessary to solve the problem of iron removal in recycled aluminum alloys.

[0003] There is an important problem in the process of recycling aluminum scrap: there are many kinds of impurities in the scrap, and impure iron will continue to accumulate in the recycling process of aluminum scrap, reaching a very high content, which is extremely difficult to purify and remove, causing difficulties in subsequent production. Therefore, the development of efficient iron removal technology is of great significance to the recycling of aluminum scrap.

[0004] The patented method for removing iron from regenerated Al-Mg-Si aluminum alloy (CN107619958B) uses Mn element to react with needle-shaped β-AlFeSi iron-rich phase to produce α-Al 15 The iron removal is carried out by combining the blocky iron phase of (Fe,Mn)3Si2 and the high-melting-point and high-density Fe2B compound generated by the reaction of KBF4 and impurity iron; in the patented method for removing iron and silicon impurities in waste aluminum regeneration (CN103740947B), a plurality of materials such as borax, manganese chloride, calcium chloride, calcium oxide, magnesium carbonate, and sulfur are mixed to prepare an iron remover. Although both iron removal methods successfully remove part of the iron impurities, they both have problems such as more preliminary preparation work, longer process flow, more complicated implementation method, low economic benefits, and poor practical applicability.

[0005] It can be seen that seeking suitable purification and smelting technology and suitable, efficient and economical flux to solve the technical problems related to the design of iron removal modification schemes and production process improvements, and obtaining high-recovery and high-purity aluminum melt has high practical significance and is also the key to solving existing technical problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method for removing iron impurities in recycled aluminum alloy to solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solution: The present invention provides a method for removing iron impurities from recycled aluminum alloy.

[0008] S1. Preparation of deironing flux: stirring, mixing and drying the deironing flux (25-45wt.% potassium borofluoride, 20-30wt.% sodium chloride, 20-35wt.%) weighed by mass percentage to obtain the deironing flux;

[0009] S2, smelting of scrap aluminum: firstly put scrap aluminum into a smelting furnace for melting, and when the molten aluminum is stirred, wrap the prepared deironing flux with aluminum foil and add it to the scrap aluminum molten liquid, and add permanganate catalyst at the same time, the deironing flux adding time is controlled within 0-5min, and the adding amount is controlled within 0.5-4wt.% of the molten liquid; when the deironing flux is added, the smelting temperature of the molten aluminum is controlled within 700-760℃; after the deironing flux is added, the scrap aluminum molten liquid is continuously stirred, and after the stirring is completed, the melt is allowed to stand for 0-120min. The molten aluminum treated with the deironing flux is obtained.

[0010] The traditional iron removal solvent Na2B4O7 will become disordered and unstable in structure when the temperature rises. After melting, it will have high viscosity and agglomeration, which makes it impossible to fully contact with the aluminum liquid, so it is difficult to obtain a relatively ideal iron removal effect. At the same time, this is also a key problem that has long plagued the field of iron removal in recycled aluminum alloys. KBF4 is used to replace the traditional Na2B4O7 iron removal agent. The viscosity of KBF4 iron removal flux is much lower than that of the traditional iron removal flux Na2B4O7 (see Table 1), which can significantly increase the contact efficiency and improve the iron removal effect.

[0011] Table 1 Comparison of viscosity of KBF4 deironing flux and borax deironing flux (MPa·s)

[0012]

[0013] In the process of iron removal, permanganate is used as a catalyst, i.e., an auxiliary agent for the iron removal flux, to (1) give the iron removal flux better activity. This allows the iron removal flux to better contact the free Fe element in the aluminum liquid; (2) improve the purity of the metal: in the process of metal refining, permanganate can reduce certain impurities and impurity oxides, promote the precipitation, dissolution or evaporation of impurities and impurity oxides, thereby improving the purity of the metal; (3) promote the reaction: adding permanganate can increase the speed and efficiency of the reaction. After adding permanganate, the reaction time of the flux can be significantly shortened and the reaction efficiency can be improved; (4) after adding permanganate, the divalent iron ions in the melt can be oxidized into trivalent iron ions, so that more iron ions and boron ions in the melt react, thereby improving the reaction rate and reaction efficiency of the flux in the melt.

[0014] The invention discloses the following technical effects: by studying the influence of the addition amount of iron removal flux (KBF4-KCl-NaCl), the holding temperature, the holding time and the permanganate catalyst on the impurity iron in the regenerated aluminum alloy, it is found that the iron mass fraction decreases with the increase of the addition amount of the boron-containing flux and the extension of the standing time; when the addition amount of KBF4 is 1.00wt.% of the aluminum melt and the standing holding time is 60min, the iron mass fraction can be reduced from 1.00wt.% to 0.56wt.% (the iron removal rate reaches 44%). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1 A diagram showing the composition of the ternary flux designed in the experiment of the present invention and its mass fraction (wt.%) in the aluminum melt;

[0017] Figure 2 A graph showing the iron removal rate (wt.%) of the KBF4 flux of the present invention;

[0018] Figure 3 A graph showing the effect of reaction time on iron content (wt.%) of the present invention;

[0019] Figure 4 This is a graph showing the effect of the standing temperature on the iron removal rate (wt.%) of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] Reference Figure 1-Figure 4 As shown, this embodiment provides a method for removing iron impurities from a recycled aluminum alloy, S1, preparing an iron removal flux: stirring, mixing and drying an iron removal flux (25-45wt.% potassium borofluoride, 20-30wt.% sodium chloride, 20-35wt.%) weighed by mass percentage to obtain an iron removal flux;

[0024] S2, scrap aluminum smelting: first put scrap aluminum into a smelting furnace to melt, and under the stirring state of the molten liquid, wrap the prepared iron removal flux with aluminum foil and add it to the scrap aluminum molten liquid, and add permanganate catalyst at the same time, the iron removal flux addition time is controlled within 0-5min, and the addition amount is controlled at 0.5-4wt.% of the molten liquid; when the iron removal flux is added, the smelting temperature of the aluminum molten liquid is controlled at 700-760℃; after the iron removal flux is added, the scrap aluminum molten liquid is continuously stirred, and after the stirring is completed, the melt is allowed to stand for 0-120min. Obtain the aluminum molten liquid treated with the iron removal flux; let it stand again for 0-10min to obtain the regenerated aluminum molten liquid with the iron impurity elements removed.

[0025] Figure 1 In the middle, 0#~4# are deironing fluxes with different proportions of KBF4 added respectively, and deironing is performed according to the proportion of the iron-making agent components;

[0026] Melting: Melt the industrial 6005 aluminum scrap raw materials. The prepared charge must be dry, clean, free of oil and dust;

[0027] Adding iron remover: adding iron remover to molten aluminum liquid, keeping the alloy at 720°C, the reaction time is 30min, 60min, 90min, 120min respectively;

[0028] Refining: Press the refining agent into the alloy liquid and continue stirring until the melt stops boiling;

[0029] Deslagging: After refining, the deslagging agent is evenly sprinkled on the surface of the melt, and the slag on the surface of the melt is removed after standing and keeping warm for 20 minutes; the refined alloy melt is solidified to obtain an ingot;

[0030] The Fe content of the alloy was analyzed and detected by spectrometer. The influence of KBF4 flux content on the iron removal effect of recycled 6005 aluminum alloy is as follows Figure 2 As shown in the figure, by comparing the iron removal rates of different flux ratios, it can be found that with the increase of KBF4 mass fraction, the iron removal rate increases, but when the KBF4 mass fraction is added to 1.00wt.%, the iron removal rate decreases with the continued increase of KBF4 mass fraction. Therefore, for KBF4 flux iron removal, the best iron removal effect is when the KBF4 mass fraction is 1.00%;

[0031] At the experimental temperature of 720℃, the components of the samples of #0-#4 flux were analyzed after being left to stand for 30min, 60min, 90min, and 120min. The experimental results are as follows: Figure 3 ;

[0032] When the reaction was carried out for 30 minutes, the mass fraction of iron decreased rapidly. When the reaction was carried out for 60 minutes, the mass fraction of iron was lower than that of the reaction for 30 minutes. When the reaction time was 90 minutes and 120 minutes, the mass fraction of iron was basically unchanged compared with that of 60 minutes, indicating that the flux had reacted completely at 60 minutes. The above results show that the iron removal time, that is, the reaction time of the flux, is preferably 60 minutes.

[0033] Select flux #3 and place at 700℃, 720℃, 740℃ and 760℃ for 60min. The experimental data are as follows: Figure 4 The best effect is achieved at 720℃, where the Fe content in the melt decreases from 1.00wt.% to 0.56wt.%. The second best effect is achieved at 740℃. When the temperature exceeds 740℃, the Fe content remains basically unchanged, so the best smelting temperature is 720℃.

[0034] When KBF4 flux is used to remove iron from recycled 6005 aluminum alloy, when a small amount of KBF4 is added, the Fe content is reduced to a certain extent. When 1.00wt.% is added, the Fe content is reduced to the maximum, and the Fe content drops to 0.68wt.% at the lowest. As the reaction time increases, the Fe content gradually decreases, and drops to the lowest at 60min. After more than 60min, the mass fraction of iron hardly changes. The best iron removal effect is achieved at 720℃, and the Fe content in the melt drops from the original 1.00wt.% to 0.56wt.%. The effect at 740℃ is second, and after the temperature exceeds 740℃, the Fe content remains basically unchanged.

[0035] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for removing iron impurities from a recycled aluminum alloy, characterized in that: The iron removal flux (25-45wt.% potassium borofluoride, 20-30wt.% sodium chloride, 20-35wt.% potassium chloride) weighed by mass percentage is stirred, mixed and dried. The prepared iron removal flux is added to the waste aluminum melt and stirred, and permanganate is added for catalysis. The temperature of the aluminum melt is controlled at 660-760°C, the adding time is controlled within 0-10min, and the adding amount is controlled at 0.5-4wt.% of the melt. After the stirring is completed, the melt is allowed to stand for 0-120min to remove iron-containing compounds, and then allowed to stand again to obtain the purified regenerated aluminum melt.

2. The method for removing iron impurities from recycled aluminum alloy according to claim 1, characterized in that The ratio of the iron removal flux in step (1) is: 30-35wt.% potassium borofluoride, 25-30wt.% sodium chloride, and 30-35wt.% potassium chloride.

3. The method for removing iron impurities from recycled aluminum alloy according to claim 1, characterized in that In step (2), the time for adding the deironing flux is controlled within 0-5 minutes, and the amount added is controlled at 2.5-4wt.% of the molten aluminum; when the deironing flux is added, the smelting temperature of the molten aluminum is controlled at 720-750°C; after the deironing flux is added, the waste aluminum molten aluminum is continuously stirred, and after the stirring is completed, the melt is allowed to stand for 30-90 minutes.

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