A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials

Abstract

The present invention discloses a method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, belonging to the field of application of recycled aluminum alloys, including: (1) sorting and charging the recycled aluminum raw materials into a furnace; (2) alloy melting; (3) removing the aluminum ash on the surface generated after melting; (4) batching and refining; (5) removing the aluminum ash on the surface generated after refining; (6) performing high-temperature treatment on the aluminum ash under a nitrogen protection atmosphere; (7) ball milling treatment; (8) vacuum high-temperature desalination; (9) high-temperature self-heating sintering to form a composite oxide; (10) screening and adding the composite oxide to the refined aluminum liquid; (11) adding a pretreated foaming agent; (12) casting a foamable preform and cooling to obtain a preform. The method of the present invention solves the problem of resource utilization of recycled aluminum and aluminum ash, not only improving the recycling rate of resources, but also providing a new raw material source for the production of preforms.

Description

Technical Field

[0001] The present invention belongs to the field of application of recycled aluminum alloys, and particularly relates to a method for preparing a foamable preform by using recycled aluminum and aluminum ash generated during its smelting process as raw materials. Background Art

[0002] Recycled aluminum has the characteristics of low price and low emissions and is developing rapidly. The Chinese recycled aluminum industry is about to face new opportunities. In recent years, with the proposal of green development, the production capacity of China's electrolytic aluminum industry has reached its limit. In order to achieve the "dual carbon" goal at an early date, the reuse of waste aluminum alloys has become very important. According to relevant data, the energy consumption for producing 1 ton of recycled aluminum is only 5% of that of primary aluminum, and the energy-saving and emission-reduction effects are obvious. However, because the sources of recycled aluminum raw materials are extensive and the components are not fixed, often containing dozens of elements such as Al, Cu, Fe, Mg, Mn, Zn, etc., it is difficult to purify, maintain the grade or prepare high-performance aluminum alloys. On the other hand, during the remelting and refining processes of recycled aluminum, a large amount of aluminum ash solid waste mainly composed of aluminum nitride, aluminum oxide and aluminum is generated. Since aluminum nitride decomposes when exposed to water, generating harmful gases such as ammonia, it is extremely difficult to store and process aluminum ash. Moreover, the aluminum ash contains refining agents such as sodium salts and potassium salts, with complex components, and it is difficult to recycle and utilize them resourcefully. How to increase the added value of recycled aluminum products and effectively utilize aluminum ash solid waste is an important problem faced by the current development of the recycled aluminum industry.

[0003] Conventional aluminum ash treatment methods are divided into two types: pyrometallurgy and hydrometallurgy. The purpose is to remove harmful components in aluminum ash and enrich valuable materials such as aluminum oxide. However, due to factors such as high treatment costs, complex processes, and low product prices, it is difficult to achieve clear economic value. Using solid-phase particles as reinforcements can prepare aluminum matrix composites, which can be further used to prepare lightweight aluminum matrix foam materials with higher added value, and are applied in fields such as automotive lightweight components and buffer energy absorption of national defense equipment. Composite solid-phase particles with special wettability (such as SiC particles) can enhance the matrix strength while providing stability for liquid foams. After adding a foaming agent to the composite material, it can be quickly cooled to prepare a foamable preform. However, the wettability between aluminum ash particles treated by conventional techniques and aluminum liquid is poor, making it difficult to mix, and the chlorides or fluorides contained in aluminum ash have a destructive effect on foam stability, making it difficult to be used to prepare high-performance aluminum matrix composites or aluminum matrix foam materials. Summary of the Invention

[0004] In view of the above existing problems, the present invention provides a method for preparing a foamable preform using recycled aluminum and aluminum ash. The present invention aims to solve the problem of resource utilization of recycled aluminum and aluminum ash, and this method can convert these materials into foamable preforms with higher added value. The method of the present invention not only improves the recycling rate of resources but also provides a new raw material source for the production of preforms.

[0005] A method for preparing a foaming preform using recycled aluminum and aluminum ash as raw materials, comprising the following steps:

[0006] (1) Sorting and charging the recycled aluminum raw materials

[0007] The recycled aluminum raw materials are screened by magnetic separation, flotation, etc. to reduce impurities such as iron, and then put into a melting furnace for preparation of melting.

[0008] (2) Alloy melting

[0009] The raw materials are melted in the melting furnace to make the temperature of the aluminum liquid reach 660°C - 680°C, the elemental composition in the aluminum liquid is detected, and targeted adjustments are made.

[0010] (3) Skimming

[0011] The aluminum ash on the surface generated after melting is removed, and the aluminum liquid is transferred to a refining furnace, and the temperature of the refining furnace is controlled at 700°C - 740°C;

[0012] (4) Batching and refining

[0013] Alloying elements including Si, Cu, Fe, Mn, Mg, Zn are added according to the target alloy composition for in-furnace stirring, the elemental composition in the aluminum liquid is detected, and targeted adjustments are made.

[0014] A refining agent is added and refined for 2h - 3h to remove the inclusion gases and solid impurities in the aluminum liquid.

[0015] (5) Skimming

[0016] The aluminum ash on the surface generated after refining is removed.

[0017] (6) Aluminum recovery treatment in aluminum ash

[0018] The aluminum ash generated in steps (2) - (5) is recovered and put into a rotary furnace, and high-temperature treatment is carried out under a nitrogen protection atmosphere to enrich the aluminum contained therein, and the enriched aluminum is returned to the melting furnace.

[0019] (7) Ball milling treatment

[0020] The aluminum ash recovered after high-temperature treatment is crushed and ball milled into fine powder with a particle size of 38μm - 100μm according to a ball-to-material ratio of 5:6.

[0021] (8) Vacuum high-temperature desalination

[0022] The ball-milled powder is put into a vacuum furnace for heating to evaporate the sodium and potassium salts in the powder, and they condense in the cooling pipe, and are recovered and returned to the refining step.

[0023] (9) High-temperature self-heating sintering

[0024] Mix the desalted fine powder and calcium oxide and then put them into a calcination furnace for calcination to obtain a composite oxide.

[0025] (10) Sieving, adding composite oxide particles to the refined aluminum liquid

[0026] Sieve the composite oxide through a 80-mesh sieve and then add it as a foam stabilizer to the refined aluminum liquid.

[0027] (11) Adding the pretreated foaming agent

[0028] Control the temperature of the aluminum liquid at 630°C - 640°C, add the pretreated foaming agent TiH2 to the aluminum liquid, and stir evenly.

[0029] (12) Casting the foamable preform

[0030] Let the aluminum liquid stand in a resistance furnace for 5s - 10s and then take it out, pour it into a mold preheated to 350°C in advance, and cool to obtain the preform.

[0031] The above method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, wherein:

[0032] In the step (4), the content of the target alloy components: Si 9.5% - 13.0%, Fe < 1.0%, Cu 1.0% - 4.0%, Mg < 1.0%, Mn < 1.0%, Zn < 3.0%, Ni < 0.5%, and the balance is aluminum and unavoidable impurities. Preferably, the target alloy is ADC12 aluminum alloy.

[0033] In the step (4), the refining agent used includes chlorides and fluorides of sodium and potassium, and the usage amount is generally 0.2% - 0.4% of the mass of the aluminum alloy melt.

[0034] In the step (6), the high-temperature treatment is carried out under a nitrogen protection atmosphere, the temperature is controlled at 620°C - 780°C, and the high-temperature treatment time is 10 min. The nitrogen treatment converts the aluminum ash into a phase structure dominated by AlN.

[0035] In the step (8), the vacuum high-temperature desalting method is: put the ball-milled powder into a vacuum furnace, heat it to 780°C - 900°C, and evacuate to below 1000 Pa and maintain for 30 min - 60 min to evaporate the sodium and potassium salts in the powder.

[0036] In step (9), the desalted fine powder and calcium oxide are mixed and then put into a calcination furnace for calcination. The addition amount of calcium oxide is 2%-4% of the mass of the fine powder, the sintering temperature is 1200°C-1400°C, and the calcination time is 20 min-40 min. The obtained composite oxide mainly consists of alumina, silica, iron oxide, magnesium oxide, and sodium oxide. The nitrogen gas generated during calcination is recovered and used for the treatment of aluminum ash.

[0037] In step (10), under the conditions of a temperature of 640°C-660°C and a stirring rate of 600 rpm-1000 rpm, a foam stabilizer is added to the refined aluminum liquid by stirring. The addition amount of the foam stabilizer is 6%-12% of the mass of the aluminum liquid, and the stirring time is 120 s-300 s.

[0038] In step (11), the addition amount of TiH2 is 1.1%-1.2% of the mass of the aluminum liquid, the stirring time is 60 s-180 s, and the stirring rate is 600 rpm-1000 rpm.

[0039] In step (11), the pretreatment means that the TiH2 powder is heated in a resistance furnace. Usually, the temperature is raised to 380°C-420°C, held for 20 min-40 min, and then cooled with the furnace.

[0040] In step (12), the obtained preform has a density of 1.4 g / cm 3 -1.7 g / cm 3 .

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. Low raw material cost and high economic value. Recycled aluminum waste is used as raw material and aluminum ash solid waste is made into a bubble stabilizer. The raw material source is wide and the cost is low. The prepared foamable preform product has higher economic benefits than ordinary aluminum alloys and has better economic value.

[0043] 2. Realize the closed-loop utilization of all resources in the whole process of preparing preforms from recycled aluminum, with high environmental benefits. The aluminum ash, a solid hazardous waste, is resourcefully utilized. The amount of aluminum ash used per unit weight is greater than or equal to the amount of aluminum ash generated. Moreover, the refining agent added in the middle process can be recycled as the raw material of the refining agent after the vacuum desalination treatment of aluminum ash. There is no waste water or solid waste discharge in the whole process, and there are good environmental benefits.

[0044] 3. The production process is carbon-saving and energy-saving. The temperature at which aluminum ash is added to the preform is low. After the composition of the aluminum liquid is adjusted, it can be mixed without heating up. The aluminum ash treatment process utilizes the thermite reaction and does not require the addition of fuel. The overall process is carbon-saving and energy-saving.

[0045] 4. Aluminum ash is used to replace the metal Ca added in the conventional preparation process of aluminum foam, further reducing the production cost. The addition of Ca during the foaming process of aluminum foam will form a hard and brittle phase CaAl2Si2 in the foam, and stress will concentrate here during compression, resulting in crack generation and indirectly forming fractures in the aluminum matrix. However, the addition of the composite oxide of the present invention can promote grain refinement and improve the material properties. The composite oxide of the present invention can replace most of the Ca to play the role of increasing viscosity and stabilizing cell pores, effectively reducing the amount of CaAl2Si2 in the foam, and the composite oxide is mainly distributed on the surface of the cell walls in the aluminum foam( Figure 8 ). Figure 11 ) Reducing the brittle fracture of cell pores caused by stress concentration. At the same time, the addition of the composite oxide effectively reduces the size of eutectic silicon grains and improves the grain distribution. Generally speaking, during the preparation process of the preform, the commonly used tackifier Ca is not added, and the addition of the composite oxide enhances the matrix strength. At the same time, through grain refinement, the problem of large brittleness of the material caused by high contents of Si, Mg, Cu, and Fe is avoided(

[0046] 5. The aluminum ash treatment process includes a vacuum desalination step to remove the influence of substances such as fluorides and chlorides that affect foaming on the subsequent foaming process. In the traditional process, after calcination and washing of aluminum ash, there are still substances such as aluminum nitride and fluorides and chlorides that affect foaming( Figure 7 ).

[0047] 6. The aluminum ash is treated under nitrogen protection to improve the recovery rate of metallic aluminum in the aluminum ash and convert the aluminum ash into a phase structure dominated by AlN. Then, through vacuum desalination and high-temperature self-thermal oxidation, a composite oxide is produced. By adding CaO, a special high specific surface area morphology is formed. It can significantly improve the wettability between the composite oxide and the aluminum liquid, and is easy to react and wet with components such as Mg and Cu with specific proportions in the alloy composition. It is easy to adsorb gas during stirring, reducing the gas release loss of the foaming agent during the stirring process. A large number of gas nuclei are generated in the preform after solidification, which helps to inhibit the liquid drainage of bubbles during the subsequent foaming process. The surface expansion range is small during the expansion process, and it is easy to obtain better surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is the process flow chart of the preparation process of the present invention;

[0049] Figure 2 is the microscopic structure of the aluminum ash without vacuum high-temperature desalination under the electron microscope in the present invention;

[0050] Figure 3 is the microscopic structure of the aluminum ash after vacuum high-temperature desalination under the electron microscope in the present invention;

[0051] Figure 4The energy spectrum diagram of the aluminum ash after vacuum high-temperature desalination in the present invention;

[0052] Figure 5 The XRD analysis of the aluminum ash that has been treated with nitrogen but not desalted in the present invention;

[0053] Figure 6 The XRD analysis of the aluminum ash after vacuum high-temperature desalination treatment in the present invention;

[0054] Figure 7 The XRD analysis of the aluminum ash after water washing treatment in the traditional process;

[0055] Figure 8 The microscopic structure of the composite oxide distributed on the surface of the bubble wall under the electron microscope in the present invention;

[0056] Figure 9 The microscopic structure of the recycled aluminum under the electron microscope after adding the composite oxide in the present invention;

[0057] Figure 10 The cross-sectional view of the preform in the present invention;

[0058] Figure 11 The compression comparison curve of the foamed aluminum formed after the preform foams in the present invention;

[0059] Figure 12 The expansion rate curve during the foaming process of the preform in the present invention. Specific Embodiments

[0060] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in the specification of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0061] Example 1

[0062] A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, the process flow is as Figure 1 shown, and the specific operation steps are as follows:

[0063] (1) Sorting and loading of recycled aluminum raw materials

[0064] The recycled aluminum raw materials recovered are subjected to screening such as magnetic separation and flotation to reduce impurities such as iron, and then put into a melting furnace for preparation of melting.

[0065] (2) Alloy melting

[0066] Melt the raw materials in a smelting furnace to make the temperature of the molten aluminum reach 660°C - 680°C, detect the elemental composition in the molten aluminum, and make targeted adjustments.

[0067] As shown in Table 1, the main component contents in the melted raw materials are: Si 6.66% - 7.15%, Cu 1.28% - 1.37%, Mg 0.307% - 0.325%, Mn 0.193% - 0.199%, Fe 0.862% - 0.890%, Zn 0.854% - 0.878%, Ni 0.0502% - 0.0547%, Al 89.13% - 89.84%. The average contents of the main components in the melted raw materials are: Si 6.94%, Cu 1.32%, Mg 0.315%, Mn 0.196%, Fe 0.875%, Zn 0.867%, Ni 0.0520%, Al 89.43%.

[0068] Table 1 Composition of the aluminum alloy after melting in the present invention

[0069]

[0070] (3) Skim the dross

[0071] Remove the aluminum ash on the surface generated after smelting, and transfer the molten aluminum to a refining furnace. The temperature of the refining furnace is controlled at 700°C - 740°C.

[0072] (4) Batching and refining

[0073] Add alloying elements such as Si, Cu, Fe, Mn, Mg, Zn, etc. according to the target alloy composition and stir in the furnace. Detect the elemental composition in the molten aluminum and make targeted adjustments.

[0074] The target alloy is ADC12 aluminum alloy, and the chemical composition content is: Si 9.6% - 12%, Fe < 0.9%, Cu 1.5% - 3.5%, Mg < 0.3%, Mn < 0.5%, Zn < 1.0%, Ni < 0.5%, and the balance is aluminum and unavoidable impurities.

[0075] Add the refining agent NaCl, and the addition amount is 0.2% of the mass of the aluminum alloy melt. Refine for 2 hours to remove the inclusion gases and solid impurities in the molten aluminum. The average component contents in the molten aluminum after refining are: Si 10.77%, Cu 1.54%, Mn 0.262%, Fe 0.859%, Mg 0.245%, Zn 0.755%, Ni 0.0465%, Al 85.52%, and unavoidable impurities. The test results and averages of four groups of experiments are shown in Table 2.

[0076] Table 2 Test results and averages of four groups of experiments

[0077]

[0078] (5) Skimming off dross

[0079] Skim off the aluminum ash on the surface generated after refining.

[0080] (6) Aluminum recovery treatment in aluminum ash

[0081] Put the aluminum ash generated in steps (2)-(5) into a rotary furnace after recovery, and carry out high-temperature treatment under a nitrogen protection atmosphere. The temperature is controlled at 620°C - 650°C, and the high-temperature treatment is carried out for 10 minutes to enrich the aluminum contained therein, and the enriched aluminum is returned to the melting furnace. Figure 5 Nitrogen treatment converts the aluminum ash into a phase structure dominated by AlN.

[0082] (7) Ball milling treatment

[0083] Crush the aluminum ash recovered after high-temperature treatment, and ball mill it into fine powder with a particle size of 38μm - 100μm according to a ball-to-material ratio of 5:6.

[0084] (8) Vacuum high-temperature desalination

[0085] Put the ball-milled powder into a vacuum furnace, heat it to 780°C - 900°C, and evacuate to below 1000 Pa and maintain for 30 minutes to evaporate the sodium salts, potassium salts, etc. in the powder and condense them in the cooling pipe, and recycle them back to the refining step. Figure 6 XRD analysis of the aluminum ash after vacuum high-temperature desalination treatment.

[0086] (9) High-temperature self-heating sintering

[0087] Mix the desalted fine powder and calcium oxide and put them into a calcination furnace. The addition amount of calcium oxide is 2% of the mass of the fine powder. Ignite the powder to raise the sintering temperature to 1200°C and calcine for 30 minutes to obtain a composite oxide mainly composed of aluminum oxide, silicon dioxide, iron oxide, magnesium oxide, and sodium oxide. The nitrogen generated by calcination is recycled for the treatment of aluminum ash.

[0088] The microscopic structure of the aluminum ash without vacuum calcination treatment is as shown in Figure 2 shown. The microscopic structure and energy spectrum of the aluminum ash after vacuum calcination are as shown in Figure 3 、 Figure 4 shown. Figure 2 In, the aluminum ash particles show irregular shapes, the particle surfaces are rough, and they may contain various different crystal structures or phases. Figure 3 In, the morphology of the aluminum ash particles after calcination is more regular, forming a specific crystal structure, the particle surfaces are smoother, and the agglomeration between particles is reduced.

[0089] (10) Sieving and adding composite oxide particles to the refined molten aluminum

[0090] Sieve the composite oxide through a 80-mesh sieve, and then, as a foam stabilizer, add it to the refined molten aluminum under the conditions of a temperature of 640°C - 660°C and a stirring rate of 1000 rpm. The addition amount of the foam stabilizer is 6% of the mass of the molten aluminum, and the stirring time is 120 s.

[0091] Figure 8 It is the microstructure of the composite oxide added to the molten aluminum under the electron microscope on the surface of the bubble wall; Figure 9 It is the microstructure of the molten aluminum after adding the composite oxide under the electron microscope.

[0092] (11) Adding the pretreated foaming agent

[0093] Control the temperature of the molten aluminum at 637°C, add the pretreated foaming agent TiH2 to the molten aluminum, and stir evenly. The addition amount of TiH2 is 1.15% of the mass of the molten aluminum, the stirring time is 60 s, and the stirring rate is 600 rpm.

[0094] (12) Casting into a foamable preform

[0095] Take out the molten aluminum from the resistance furnace after standing for 5 s - 10 s, pour it into a mold preheated to 350°C in advance, and cool to obtain the preform. The density of the preform is 1.44 g / cm 3 .

[0096] The cross-section of the prepared preform is as Figure 10 shown, and the compression comparison curve of the foam aluminum formed after the preform foams is as Figure 11 shown, and the expansion rate curve is as Figure 12 shown. It can be seen from Figure 11 that for the aluminum-based foam material prepared by adding 6% composite oxide as a foam stabilizer, the fluctuation of the compression curve is significantly smaller than that of the aluminum-based foam material prepared by adding 3% metallic Ca as a viscosity-increasing agent, which significantly improves the overall mechanical properties and energy absorption. It can be seen from Figure 12 that after about 15 min, the expansion rate during the foaming process of the preform begins to increase significantly, indicating that the material begins to undergo rapid thermal expansion. The shape of the entire curve indicates that the expansion rate is a function of time, and within a specific time range, the expansion rate will increase significantly.

[0097] Example 2

[0098] A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, the process flow is as Figure 1 shown, and the specific operation steps are as follows:

[0099] (1) Sorting and loading the recycled aluminum raw materials

[0100] The recycled secondary aluminum raw materials are subjected to screening such as magnetic separation and flotation to reduce impurities such as iron, and then put into a melting furnace for preparation of melting.

[0101] (2) Alloy melting

[0102] The raw materials are melted in the melting furnace to make the temperature of the aluminum liquid reach 660°C - 680°C, and the elemental composition in the aluminum liquid is detected and adjusted accordingly.

[0103] As shown in Table 1, the main component contents in the melted raw materials are: Si 6.66% - 7.15%, Cu 1.28% - 1.37%, Mg 0.307% - 0.325%, Mn 0.193% - 0.199%, Fe 0.862% - 0.890%, Zn 0.854% - 0.878%, Ni 0.0502% - 0.0547%, Al 89.13% - 89.84%. The average main component contents in the melted raw materials are: Si 6.94%, Cu 1.32%, Mg 0.315%, Mn 0.196%, Fe 0.875%, Zn 0.867%, Ni 0.0520%, Al 89.43%.

[0104] (3) Skimming

[0105] The aluminum ash on the surface generated after melting is removed, and the aluminum liquid is transferred to a refining furnace, and the temperature of the refining furnace is controlled at 700°C - 740°C.

[0106] (4) Batching and refining

[0107] Alloying elements such as Si, Cu, Fe, Mn, Mg, and Zn are added according to the target alloy composition for in-furnace stirring, and the elemental composition in the aluminum liquid is detected and adjusted accordingly.

[0108] The target alloy is ZL108 aluminum alloy, and its composition content is: Si 11.0% - 13.0%, Fe < 1.0%, Cu 1.0% - 2.0%, Mg 0.4% - 1.0%, Mn < 0.9%, Zn < 1.0%, Ni < 0.05%, and the balance is aluminum and unavoidable impurities.

[0109] Refining agent NaCl is added, 0.3% of the mass of the aluminum alloy melt, and refined for 3 hours to remove the inclusion gases and solid-phase impurities in the aluminum liquid. The average component contents in the refined aluminum liquid are: Si 12%, Cu 1.5%, Mn 0.223%, Fe 0.746%, Mg 0.470%, Zn 0.973%, and the balance is aluminum and unavoidable impurities.

[0110] (5) Skimming

[0111] The aluminum ash on the surface generated after refining is removed.

[0112] (6) Aluminum recovery and treatment from aluminum ash

[0113] The aluminum ash generated in steps (2)-(5) is recycled and placed in a rotary kiln for high-temperature treatment under a nitrogen protection atmosphere. The temperature is controlled at 650°C - 700°C, and the high-temperature treatment is carried out for 10 minutes to enrich the aluminum contained therein. The enriched aluminum is returned to the melting furnace.

[0114] (7) Ball milling treatment

[0115] The aluminum ash recovered after high-temperature treatment is crushed and ball milled into fine powder with a particle size of 38μm - 100μm according to a ball-to-material ratio of 5:6.

[0116] (8) Vacuum high-temperature desalination

[0117] The ball-milled powder is placed in a vacuum furnace and heated to 780°C - 900°C, and the air is pumped to below 1000 Pa and maintained for 40 minutes to evaporate the sodium salts and potassium salts in the powder, which condense in the cooling pipe and are recycled and returned to the refining step.

[0118] (9) High-temperature self-heating sintering

[0119] The desalted fine powder and calcium oxide are mixed and placed in a calcination furnace. The addition amount of calcium oxide is 3% of the mass of the fine powder. The powder is ignited to raise the sintering temperature to 1300°C and calcined for 20 minutes to obtain a composite oxide mainly composed of aluminum oxide, silicon dioxide, iron oxide, magnesium oxide, and sodium oxide. The nitrogen gas generated during calcination is recycled for the treatment of aluminum ash.

[0120] (10) Screening and adding composite oxide particles to the refined aluminum liquid

[0121] The composite oxide is sieved through a 80-mesh sieve and then used as a foam stabilizer. Under the conditions of a temperature of 640°C - 660°C and a stirring rate of 800 rpm, it is added to the refined aluminum liquid. The addition amount of the foam stabilizer is 12% of the mass of the aluminum liquid, and the stirring time is 180 s.

[0122] (11) Adding the pretreated foaming agent

[0123] The temperature of the aluminum liquid is controlled at 630°C, and the pretreated foaming agent TiH2 is added to the aluminum liquid and stirred evenly. The addition amount of TiH2 is 1.2% of the mass of the aluminum liquid, the stirring time is 180 s, and the stirring rate is 800 rpm.

[0124] (12) Casting into a foamable preform

[0125] Take out the molten aluminum after standing in the resistance furnace for 5 s - 10 s, pour it into a mold preheated to 350 °C in advance, and cool to obtain a preform. The density of the preform is 1.69 g / cm 3 .

[0126] Example 3

[0127] A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, the process flow is as Figure 1 shown, and the specific operation steps are as follows:

[0128] (1) Sorting and charging of recycled aluminum raw materials

[0129] Perform magnetic separation, flotation and other screening on the recycled aluminum raw materials recovered to reduce impurities such as iron in them, and then put them into the melting furnace to prepare for melting.

[0130] (2) Alloy melting

[0131] Melt the raw materials in the melting furnace to make the temperature of the molten aluminum reach 660 °C - 680 °C, detect the elemental composition in the molten aluminum, and make targeted adjustments.

[0132] As shown in Table 1, the main component contents in the melted raw materials are: Si 6.66% - 7.15%, Cu 1.28% - 1.37%, Mg 0.307% - 0.325%, Mn 0.193% - 0.199%, Fe 0.862% - 0.890%, Zn 0.854% - 0.878%, Ni 0.0502% - 0.0547%, Al 89.13% - 89.84%. The average main component contents in the melted raw materials are: Si 6.94%, Cu 1.32%, Mg 0.315%, Mn 0.196%, Fe 0.875%, Zn 0.867%, Ni 0.0520%, Al 89.43%.

[0133] (3) Skimming

[0134] Scrape out the aluminum ash on the surface generated after melting, and transfer the molten aluminum to the refining furnace. The temperature of the refining furnace is controlled at 700 °C - 740 °C.

[0135] (4) Batching and refining

[0136] Add alloying elements such as Si, Cu, Fe, Mn, Mg, Zn, etc. according to the target alloy composition and stir in the furnace. Detect the elemental composition in the molten aluminum and make targeted adjustments.

[0137] The target alloy is YL113 aluminum alloy, and its component contents are as follows: Si 9.5%-11.5%, Fe < 1.0%, Cu 2.0%-3.0%, Mg ≤ 0.1%, Mn < 0.5%, Zn < 2.9%, Ni < 0.3%, and the balance is aluminum and inevitable impurities.

[0138] The refining agent added is a mixture of NaCl and KCl with a mass ratio of 1:1, and the addition amount is 0.4% of the mass of the aluminum alloy melt. After refining for 2.5 h, the inclusion gases and solid impurities in the aluminum liquid are removed. The average component contents in the refined aluminum liquid are: Si 11%, Mg 0.1%, Cu 2.3%, Fe 0.52%, Mn 0.34%, Zn 0.08%, and the balance is aluminum and inevitable impurities.

[0139] (5) Skimming the slag

[0140] The aluminum ash on the surface generated after refining is removed.

[0141] (6) Recycling and treatment of aluminum in aluminum ash

[0142] The aluminum ash generated in steps (2)-(5) is recycled and put into a rotary furnace. Under the protection of a nitrogen atmosphere, high-temperature treatment is carried out at a temperature controlled at 700°C-780°C for 10 min to enrich the aluminum contained therein, and the enriched aluminum is returned to the melting furnace.

[0143] (7) Ball milling treatment

[0144] The aluminum ash recovered after high-temperature treatment is crushed and ball milled into fine powder with a particle size of 38 μm-100 μm according to a ball-to-material ratio of 5:6.

[0145] (8) Vacuum high-temperature desalination

[0146] The ball-milled powder is put into a vacuum furnace and heated to 780°C-850°C, and the air is pumped to below 1000 Pa and maintained for 60 min to evaporate the sodium salts and potassium salts in the powder, and they condense in the cooling pipe. After recovery, they are returned to the refining step.

[0147] (9) High-temperature self-heating sintering

[0148] The desalted fine powder and calcium oxide are mixed and then put into a calcination furnace. The addition amount of calcium oxide is 4% of the mass of the fine powder. The powder is ignited to raise the sintering temperature to 1400°C and calcined for 20 min to obtain a composite oxide mainly composed of aluminum oxide, silicon dioxide, iron oxide, magnesium oxide, and sodium oxide. The nitrogen gas generated during calcination is recovered for the treatment of aluminum ash.

[0149] (10) Screening and adding composite oxide particles to the refined aluminum liquid

[0150] The composite oxide is sieved through a 80-mesh sieve and then used as a foam stabilizer. It is added into the refined molten aluminum at a temperature of 640°C - 660°C and a stirring rate of 600 rpm. The addition amount of the foam stabilizer is 10% of the mass of the molten aluminum, and the stirring time is 300 s.

[0151] (11) Add the pretreated foaming agent

[0152] Control the temperature of the molten aluminum at 640°C, add the pretreated foaming agent TiH2 into the molten aluminum, and stir evenly. The addition amount of TiH2 is 1.2% of the mass of the molten aluminum, the stirring time is 120 s, and the stirring rate is 1000 rpm.

[0153] (12) Cast into a foamable preform

[0154] Let the molten aluminum stand in the resistance furnace for 5 s - 10 s and then take it out. Pour it into a mold preheated to 350°C in advance and cool to obtain the preform. The density of the preform is 1.58 g / cm 3 .

Claims

1. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials, characterized in that, It includes the following steps: (1) Sorting and charging of recycled aluminum raw materials: The recycled aluminum raw materials are subjected to magnetic separation and flotation screening to reduce impurities therein, and then put into a melting furnace for preparation of melting; (2) Alloy melting: The raw materials are melted in the melting furnace to make the temperature of the aluminum liquid reach 660°C - 680°C, and the elemental composition in the aluminum liquid is detected; (3) Skimming: The aluminum ash on the surface generated after melting is removed, and the aluminum liquid is transferred to a refining furnace, and the temperature of the refining furnace is controlled at 700°C - 740°C; (4) Batching and refining: Alloying elements including Si, Cu, Fe, Mn, Mg, and Zn are added according to the target alloy composition for in-furnace stirring, and the elemental composition of each element in the aluminum liquid is detected; A refining agent is added, and refining is carried out for 2h - 3h to remove the inclusion gas and solid-phase impurities in the aluminum liquid; (5) Skimming: The aluminum ash on the surface generated after refining is removed; (6) Recycling treatment of aluminum in aluminum ash: The aluminum ash generated in steps (2) - (5) is recycled and put into a rotary furnace, and high-temperature treatment is carried out under a nitrogen protection atmosphere, the temperature is controlled at 620°C - 780°C, the high-temperature treatment time is 10 min, and the nitrogen treatment converts the aluminum ash into a phase structure dominated by AlN and enriches the aluminum contained therein, and the enriched aluminum is returned to the melting furnace; (7) Ball milling treatment: The aluminum ash recovered after high-temperature treatment is crushed and ball milled into fine powder with a particle size of 38μm - 100μm according to a ball-to-material ratio of 5:6; (8) Vacuum high-temperature desalting: The ball-milled powder is put into a vacuum furnace for heating to evaporate the sodium and potassium salts in the powder, and they condense in the cooling pipe, and are recycled and returned to the refining step; (9) High-temperature self-heating sintering: The desalted fine powder and calcium oxide are mixed and then put into a calcining furnace for calcination, and the addition amount of calcium oxide is 2% - 4% of the mass of the fine powder to obtain a composite oxide; (10) Screening and adding composite oxide particles to the refined aluminum liquid: The composite oxide is sieved through a 80-mesh sieve and added as a foam stabilizer to the refined aluminum liquid; (11) Adding the pretreated foaming agent: The temperature of the aluminum liquid is controlled at 630°C - 640°C, and the pretreated foaming agent TiH2 is added to the aluminum liquid and stirred evenly; (12) Casting a foamable preform: The aluminum liquid was placed in the resistance furnace for 5s-10s and then taken out and cast into a mold preheated to 350°C. The preform was cooled to obtain a preform with a density of 1.4g / cm 3 -1.7g / cm 3 .

2. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (4), the content of the target alloy components: Si 9.5% - 13.0%, Fe < 1.0%, Cu 1.0% - 4.0%, Mg < 1.0%, Mn < 1.0%, Zn < 3.0%, Ni < 0.5%, and the balance is aluminum and inevitable impurities.

3. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (4), the used refining agent includes chlorides and fluorides of sodium and potassium, and the usage amount is 0.2% - 0.4% of the mass of the aluminum alloy melt.

4. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (8), the vacuum high-temperature desalting method is: putting the ball-milled powder into a vacuum furnace and heating it to 780°C - 900°C, and pumping air to below 1000 Pa and maintaining it for 30 min - 60 min to evaporate the sodium and potassium salts in the powder.

5. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (9), the sintering temperature is 1200°C - 1400°C, and the calcination time is 20 min - 40 min.

6. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (10), under the conditions of a temperature of 640°C - 660°C and a stirring rate of 600 rpm - 1000 rpm, the foam stabilizer is added to the refined aluminum liquid by stirring.

7. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (10), the addition amount of the foam stabilizer is 6% - 12% of the mass of the aluminum liquid, and the stirring time is 120 s - 300 s.

8. A method for preparing a foamable preform using recycled aluminum and aluminum ash as raw materials according to claim 1, characterized in that, In the step (11), the addition amount of TiH2 is 1.1% - 1.2% of the mass of the aluminum liquid, the stirring time is 60 s - 180 s, and the stirring rate is 600 rpm - 1000 rpm; the pretreatment means that the TiH2 powder is heated in an electric resistance furnace, heated to 380°C - 420°C, held for 20 min - 40 min, and then cooled with the furnace.

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