Regulation and control method for impurity elements in recycled aluminum melt

Abstract

The invention provides a method for regulating and controlling impurity elements of recycled aluminum melt, and belongs to the technical field of recycled aluminum smelting. In order to solve the technical problems of more impurities, complex components, low melt purity and the like of recycled aluminum, a special refining agent and a refining technology are researched and developed, and a multi-filtering and online degassing technology is adopted. Specifically, firstly, graphene, calcium nitride, sodium tetraborate and the like are used as main components, and a refining agent is obtained after mixing and spheroidizing; meanwhile, brown aluminum oxide is used as a framework to construct a filter material green body, and the filter material green body contains components such as polymerized aluminum oxalate and polymerized aluminum citrate, so that impurity metal ions are effectively fixed while physical filtration is realized; and on the basis, the aluminum melt is subjected to injection refining twice, then flows through a degassing box arranged on a launder to be subjected to online degassing, and then is subjected to multiple filtration, so that the high-purity aluminum melt is obtained. The method can significantly reduce the content of impurity elements, alkali metals and hydrogen in the recovered aluminum melt, and improve the physical and chemical properties of the regenerated material.

Description

Technical Field

[0001] The present invention relates to the technical field of recycled aluminum smelting, and in particular to a method for controlling impurity elements in recycled aluminum melt. Background Art

[0002] Remelting is a fundamental and critical technology in aluminum scrap recycling. It heats collected aluminum scrap to its melting point, where it melts into a liquid state. This process utilizes aluminum's excellent thermal conductivity and low melting point to create a high-temperature environment using equipment such as furnaces. Common furnace types include reverberatory furnaces and induction furnaces. Reverberatory furnaces heat the aluminum scrap using heat generated by fuel combustion, offering large capacity and the ability to process a wide variety of scrap types. Induction furnaces utilize electromagnetic induction to generate eddy currents within the scrap, resulting in rapid heating and high thermal efficiency. The remelted aluminum can be cast into ingots of varying specifications or used directly to produce new aluminum products. This technology is unique in its ability to process aluminum scrap on a large scale, enabling rapid recycling of aluminum resources. However, the remelting process consumes significant energy, and excessive impurity levels in the scrap can compromise the quality of the recycled aluminum.

[0003] Impurities in recycled aluminum primarily include metallic elements such as iron, manganese, and copper, as well as non-metallic impurities such as silicates and oxides. These impurities significantly impact the purity and properties of aluminum, necessitating rigorous treatment and removal during the recycling process. Excessive levels of impurities such as iron and copper in scrap aluminum can reduce the strength and corrosion resistance of the recycled aluminum. Manganese can form high-melting-point iron-rich phase compounds in aluminum, aiding in iron removal, but excessive manganese can reduce the aluminum's plasticity. Non-metallic impurities such as silicates and oxides can reduce aluminum's electrical conductivity and mechanical properties. Refining and filtration are the typical methods used to address impurity issues in recycled aluminum. Traditional refining processes involve adding flux to the molten aluminum during the smelting process to prevent oxidation caused by contact with air, and using agitation to promote the separation of inclusions and hydrogen. This process is then combined with filtration to remove impurities. However, conventional refining and filtration processes currently offer limited impurity removal rates, resulting in low melt purity and negatively impacting product performance. Summary of the Invention

[0004] The present invention aims to address the technical defects of the prior art and provide a method for regulating the recovery of impurity elements in aluminum melt to solve the technical problem that conventional refining and filtration processes have a low impurity removal rate.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A method for controlling and recovering impurity elements in aluminum melt, comprising: 1) Using the following ingredients in parts by weight as raw materials: 3-6 parts of graphene, 6-10 parts of calcium nitride, 2-4 parts of titanium dioxide, 1-3 parts of ammonium fluoroborate, 0.8-1.6 parts of zeolite powder, 0.4-0.8 parts of aluminum oxide, 0.1-0.3 parts of potassium sulfate, 4-6 parts of sodium tetraborate, and 0.1-0.3 parts of magnesium aluminum silicate; after mixing the raw materials, ball milling was performed under a nitrogen atmosphere at a ball-to-material ratio of 12:1-16:1 and a rotation speed of 3000-4000 rpm for 6-10 minutes to obtain a refining agent; 2) Mix 75% alumina powder and 25% aluminum powder by mass and grind them together in a vibration mill to a particle size of d 50 <2μm to obtain a composite material; mixing 81%-84% of brown corundum, 6-8% of the composite material, 7%-9% of polyaluminum oxalate and 2%-3% of polyaluminum citrate, adding 5%-6% of water, stirring in a wheel mill for 10-15 minutes, then pounding into a filter material shape, processing and trimming, and drying at 150°C for 10-15 hours to obtain a green material; calcining the green material at 1200-1250°C for 1-1.5 hours, and then cooling to obtain a filter material; 3) sorting the scrap aluminum and removing surface moisture from the scrap aluminum; feeding the scrap aluminum processed as described above into a smelting furnace for smelting to obtain an aluminum melt, and continuously stirring the aluminum melt with a stirring device during the smelting process to precipitate some slag; spraying and refining the aluminum melt twice with an inert gas and the refining agent obtained in step 1); passing the aluminum melt through a degassing box provided on a launder for online degassing; and passing the aluminum melt through a filter box provided on the launder for online filtration 2 to 3 times, using the filter material obtained in step 2) as the filter material.

[0006] Preferably, the method further includes the following step 4): using the aluminum melt filtered in step 3) as raw material, forming an aluminum alloy melt with a ratio of 3.2% to 4.5% Co, 0.9% to 1.7% Fe, 0.02% to 0.12% Ti, and the remainder being the raw materials, and pouring the melt into a casting mold to obtain an aluminum alloy round ingot.

[0007] Preferably, the weight proportions of the raw materials in step 1) are as follows: 4 parts of graphene, 7.5 parts of calcium nitride, 3.3 parts of titanium dioxide, 1.6 parts of ammonium fluoroborate, 1.4 parts of zeolite powder, 0.5 parts of aluminum oxide, 0.2 parts of potassium sulfate, 5 parts of sodium tetraborate, and 0.2 parts of magnesium aluminum silicate.

[0008] Preferably, in step 1), the ball milling time is 8 to 8.5 minutes, the rotation speed of the spherical graphite is 3200 to 3500 rpm, and the ball-to-material ratio is 13:1.

[0009] Preferably, in step 2), the filter material is in the form of a filter plate, and the thickness of the filter plate is 2-3 cm.

[0010] Preferably, in step 2), the mass fractions of brown corundum, the composite material, polymerized aluminum oxalate, and polymerized aluminum citrate are 80%, 8%, 9%, and 3% respectively; and the mass fraction of the added water is 5.5%.

[0011] Preferably, in step 2), the stirring time in the wheel mill is 12 minutes; the drying time is 12-13 hours; and the sintering temperature of the green body material is 1220-1230° C. for 1.2 hours.

[0012] Preferably, a graphite rotor is provided in the degassing box in step 3), the rotation speed of the graphite rotor is 800-1000 rpm, the mixed gas flow rate on the graphite rotor is 6-7 cubic meters / hour, and the mixed gas pressure is 0.8-1 MPa; wherein the mixed gas is a mixed gas consisting of argon with a purity of ≥99.9% and chlorine with a purity of ≥99.9%, wherein the volume percentage of chlorine is 20-30%.

[0013] Preferably, in step 3), the amount of the refining agent used is 0.2% to 0.4% of the total weight of the aluminum melt.

[0014] Preferably, in step 3), at least two stages of filter plates are provided in the filter box.

[0015] The present invention provides a method for regulating impurity elements in recycled aluminum melt. This technical solution addresses the technical difficulties of recycled aluminum with many impurities, complex components, and low melt purity. It develops special refining agents and refining technologies, adopts multiple filtration and online degassing technologies, and promotes their application in the direct production of high-performance aluminum alloy round ingots from recycled aluminum. Specifically, the present invention first uses graphene, calcium nitride, sodium tetraborate, etc. as main components, and obtains a refining agent by mixing spheroidal graphite; at the same time, brown corundum is used as a skeleton to construct a filter material blank, which contains alumina micropowder, metallic aluminum powder, polyaluminum oxalate, and polyaluminum citrate, which effectively fixes impurity metal ions while achieving physical filtration; on this basis, the aluminum melt is subjected to two spray refining processes, and then flows through a degassing box set on the flow trough for online degassing, and then multiple filtrations are performed to obtain a high-purity aluminum melt. The present invention can significantly reduce the content of impurity elements, alkali metals, and hydrogen in the recycled aluminum melt, and improve the physical and chemical properties of the recycled material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 2 is a diagram of the impurity content detection structure of each embodiment of the present invention.

[0017] Figure 2 1 is a graph showing the tensile strength test results of the alloy materials of various embodiments of the present invention.

[0018] Figure 31 is a graph showing the electrical conductivity test results of the alloy materials of various embodiments of the present invention.

[0019] Figure 4 1 is a graph showing the corrosion resistance test results of the alloy materials of various embodiments of the present invention. DETAILED DESCRIPTION

[0020] The following is a detailed description of specific embodiments of the present invention. To avoid excessive unnecessary detail, well-known structures or functions will not be described in detail in the following examples. Approximate language used in the following examples can be used for quantitative expression to indicate that a certain amount of variation is allowed without changing the basic function. Unless otherwise defined, technical and scientific terms used in the following examples have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0021] Example 1 A method for controlling and recovering impurity elements in aluminum melt, comprising: 1) The following ingredients in parts by weight are used as raw materials: 3 parts graphene, 6 parts calcium nitride, 2 parts titanium dioxide, 1 part ammonium fluoroborate, 0.8 parts zeolite powder, 0.4 parts aluminum oxide, 0.1 part potassium sulfate, 4 parts sodium tetraborate, and 0.1 part magnesium aluminum silicate; the raw materials are mixed and ball milled under a nitrogen atmosphere at a ball-to-material ratio of 12:1 and a rotation speed of 3000 rpm for 6 minutes to obtain a refining agent; 2) Mix 75% alumina powder and 25% aluminum powder by mass and grind them together in a vibration mill to a particle size of d 50 <2μm to obtain a composite material; 82% of brown corundum, 7% of the composite material, 8% of polyaluminum oxalate and 3% of polyaluminum citrate were mixed, and 5% of water was added, and the mixture was stirred in a wheel mill for 10 minutes, and then pounded into a filter material shape, processed and trimmed, and dried at 150°C for 10 hours to obtain a green material; the green material was sintered at 1200°C for 1 hour, and then cooled to obtain a filter material; 3) sorting the scrap aluminum and removing surface moisture from the scrap aluminum; feeding the treated scrap aluminum into a smelting furnace for smelting to obtain an aluminum melt, and continuously stirring the aluminum melt with a stirring device during the smelting process to cause some slag to precipitate; spraying and refining the aluminum melt twice with an inert gas and the refining agent obtained in step 1), with the amount of the refining agent used in each refining being 0.4% of the total weight of the aluminum melt; passing the aluminum melt through a degassing box provided on a launder for online degassing; and passing the aluminum melt through a filter box provided on the launder for online filtration twice, using the filter material obtained in step 2) as the filter material; 4) Using the filtered aluminum melt in step 3) as a raw material, forming an aluminum alloy melt with a ratio of 3.2% Co, 0.9% Fe, 0.02% Ti, and the remainder as the raw materials, and pouring it into a casting mold to obtain an aluminum alloy round ingot.

[0022] The aluminum melt after filtration in step 3) was sampled and tested for impurity elements, alkali metals, and hydrogen content. The test results showed that the total impurity element content in the aluminum melt was 0.093%, the alkali metal content was 0.009%, and the hydrogen content was 0.007%.

[0023] Samples of the aluminum alloy ingots prepared above were taken and tested for tensile strength, electrical conductivity, and corrosion resistance. The tensile strength test was conducted according to GB / T 228.1-2021, the electrical conductivity according to GB / T 3048.2-2007, and the corrosion resistance test according to GB / T 10125-2021, using a neutral salt spray test at 35°C and a 5% NaCl aqueous solution. The test results showed a tensile strength of 261 MPa, a conductivity of 64.7% IACS, and a corrosion resistance of 2620 h.

[0024] Example 2 A method for controlling and recovering impurity elements in aluminum melt, comprising: 1) The following ingredients in parts by weight are used as raw materials: 6 parts of graphene, 10 parts of calcium nitride, 4 parts of titanium dioxide, 3 parts of ammonium fluoroborate, 1.6 parts of zeolite powder, 0.8 parts of aluminum oxide, 0.3 parts of potassium sulfate, 6 parts of sodium tetraborate, and 0.3 parts of magnesium aluminum silicate; the raw materials are mixed and ball milled under a nitrogen atmosphere at a ball-to-material ratio of 16:1 and a rotation speed of 4000 rpm for 10 minutes to obtain a refining agent; 2) Mix 75% alumina powder and 25% aluminum powder by mass and grind them together in a vibration mill to a particle size of d 50 <2μm to obtain a composite material; 84% of brown corundum, 6% of the composite material, 8% of polyaluminum oxalate and 2% of polyaluminum citrate were mixed, and 6% of water was added, and the mixture was stirred in a wheel mill for 15 minutes, and then pounded into a filter material shape, processed and trimmed, and dried at 150°C for 15 hours to obtain a green material; the green material was sintered at 1250°C for 1.5 hours, and then cooled to obtain a filter material; 3) sorting the scrap aluminum and removing surface moisture from the scrap aluminum; feeding the treated scrap aluminum into a smelting furnace for smelting to obtain an aluminum melt, and continuously stirring the aluminum melt with a stirring device during the smelting process to cause some slag to precipitate; spraying and refining the aluminum melt twice with an inert gas and the refining agent obtained in step 1), with the amount of the refining agent used in each refining being 0.2% of the total weight of the aluminum melt; passing the aluminum melt through a degassing box provided on a launder for online degassing; and passing the aluminum melt through a filter box provided on the launder for online filtration three times, using the filter material obtained in step 2) as the filter material; 4) Using the filtered aluminum melt in step 3) as a raw material, forming an aluminum alloy melt with a ratio of 4.5% Co, 1.7% Fe, 0.12% Ti, and the remainder as the raw materials, and pouring it into a casting mold to obtain an aluminum alloy round ingot.

[0025] The aluminum melt filtered in step 3) was sampled and tested for impurity elements, alkali metals, and hydrogen. The test results showed a total impurity element content of 0.077%, an alkali metal content of 0.006%, and a hydrogen content of 0.005%. The aluminum alloy round ingots prepared above were sampled and tested for tensile strength, electrical conductivity, and corrosion resistance. Using the same testing methods as above, the results showed a tensile strength of 252 MPa, an electrical conductivity of 63.0% IACS, and a corrosion resistance of 2680 h.

[0026] Example 3 A method for controlling and recovering impurity elements in aluminum melt, comprising: 1) The following ingredients in parts by weight were used as raw materials: 4 parts graphene, 7.5 parts calcium nitride, 3.3 parts titanium dioxide, 1.6 parts ammonium fluoroborate, 1.4 parts zeolite powder, 0.5 parts aluminum oxide, 0.2 parts potassium sulfate, 5 parts sodium tetraborate, and 0.2 parts magnesium aluminum silicate; the raw materials were mixed and ball milled under a nitrogen atmosphere at a ball-to-material ratio of 13:1 and a rotation speed of 3300 rpm for 8.3 minutes to obtain a refining agent; 2) Mix 75% alumina powder and 25% aluminum powder by mass and grind them together in a vibration mill to a particle size of d 50 <2μm to obtain a composite material; 83% of brown corundum, 7% of the composite material, 7% of polyaluminum oxalate and 3% of polyaluminum citrate were mixed, 5.5% of water was added, and the mixture was stirred in a wheel mill for 12 minutes, and then pounded into a filter material shape, processed and trimmed, and dried at 150°C for 12.5 hours to obtain a green material; the green material was sintered at 1220-1230°C for 1.2 hours, and then cooled to obtain a filter material; 3) sorting the scrap aluminum and removing surface moisture from the scrap aluminum; feeding the treated scrap aluminum into a smelting furnace for smelting to obtain an aluminum melt, and continuously stirring the aluminum melt with a stirring device during the smelting process to cause some slag to precipitate; spraying and refining the aluminum melt twice with an inert gas and the refining agent obtained in step 1), with the amount of the refining agent used in each refining being 0.3% of the total weight of the aluminum melt; passing the aluminum melt through a degassing box provided on a launder for online degassing; and passing the aluminum melt through a filter box provided on the launder for online filtration twice, using the filter material obtained in step 2) as the filter material; 4) Using the filtered aluminum melt in step 3) as a raw material, forming an aluminum alloy melt with a ratio of 4% Co, 1.3% Fe, 0.07% Ti, and the remainder as the raw materials, and pouring it into a casting mold to obtain an aluminum alloy round ingot.

[0027] In step 2), the filter material is in the form of a filter plate with a thickness of 2.5 cm. The degassing box described in step 3) is equipped with a graphite rotor, which rotates at a speed of 900 rpm. The mixed gas flow rate on the graphite rotor is 6.5 cubic meters per hour, and the mixed gas pressure is 0.9 MPa. The mixed gas is composed of argon with a purity of ≥99.9% and chlorine with a purity of ≥99.9%, with the volume percentage of chlorine being 25%. In step 3), the filter box is equipped with two stages of filter plates.

[0028] The aluminum melt filtered in step 3) was sampled and tested for impurity elements, alkali metals, and hydrogen. The test results showed a total impurity element content of 0.069%, an alkali metal content of 0.005%, and a hydrogen content of 0.003%. The aluminum alloy round ingots prepared above were sampled and tested for tensile strength, electrical conductivity, and corrosion resistance. Using the same testing methods as above, the results showed a tensile strength of 265 MPa, an electrical conductivity of 66.9% IACS, and a corrosion resistance of 2800 h.

[0029] Example 4 Commercially available finished aluminum ingots were used as raw materials, and an aluminum alloy melt was formed with a ratio of 4% Co, 1.3% Fe, 0.07% Ti, and the remainder being the raw materials, and then poured into a mold to obtain an aluminum alloy round ingot. The above-mentioned aluminum ingots were sampled, and the impurity elements, alkali metal and hydrogen contents therein were respectively detected. The test results showed that the total impurity element content in the aluminum melt was 0.128%, the alkali metal content was 0.011%, and the hydrogen content was 0.008%. The aluminum alloy round ingots prepared above were sampled, and their tensile strength, electrical conductivity and corrosion resistance were respectively tested. The detection method was the same as before, and the test results showed that the material had a tensile strength of 245 MPa, a conductivity of 58.3% IACS, and a corrosion resistance of 2210h.

[0030] The above experimental results show that the present invention can significantly reduce the content of impurity elements, alkali metals and hydrogen in recycled aluminum melt, improve the physical and chemical properties of the aluminum alloy material prepared therefrom, and is not inferior to the aluminum alloy material prepared from non-recycled aluminum in terms of tensile strength, conductivity and corrosion resistance.

[0031] The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the scope of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for controlling the recovery of impurity elements in aluminum melt, characterized in that: include: 1) Using the following ingredients in parts by weight as raw materials: 3-6 parts of graphene, 6-10 parts of calcium nitride, 2-4 parts of titanium dioxide, 1-3 parts of ammonium fluoroborate, 0.8-1.6 parts of zeolite powder, 0.4-0.8 parts of aluminum oxide, 0.1-0.3 parts of potassium sulfate, 4-6 parts of sodium tetraborate, and 0.1-0.3 parts of magnesium aluminum silicate; after mixing the raw materials, ball milling was performed under a nitrogen atmosphere at a ball-to-material ratio of 12:1-16:1 and a rotation speed of 3000-4000 rpm for 6-10 minutes to obtain a refining agent; 2) Mix 75% alumina powder and 25% aluminum powder by mass and grind them together in a vibration mill to a particle size of d 50 <2μm to obtain a composite material; mixing 81%-84% of brown corundum, 6-8% of the composite material, 7%-9% of polyaluminum oxalate and 2%-3% of polyaluminum citrate, adding 5%-6% of water, stirring in a wheel mill for 10-15 minutes, then pounding into a filter material shape, processing and trimming, and drying at 150°C for 10-15 hours to obtain a green material; calcining the green material at 1200-1250°C for 1-1.5 hours, and then cooling to obtain a filter material; 3) Sorting the scrap aluminum and removing surface moisture from the scrap aluminum; feeding the processed scrap aluminum into a smelting furnace for smelting to obtain an aluminum melt, and continuously stirring the aluminum melt with a stirring device during the smelting process to cause some slag to settle; refining the aluminum melt twice with an inert gas and the refining agent obtained in step 1); and passing the aluminum melt through a degassing box provided on a launder for online degassing. The aluminum melt is passed through a filter box arranged on the flow channel for 2 to 3 times for online filtration treatment, and the filter material used is the filter material obtained in step 2).

2. The method for controlling the recovery of impurity elements in aluminum melt according to claim 1, characterized in that: The method also includes the following step 4): using the aluminum melt filtered in step 3) as raw material, forming an aluminum alloy melt with a ratio of 3.2% to 4.5% Co, 0.9% to 1.7% Fe, 0.02% to 0.12% Ti, and the remainder being the raw materials, and pouring it into a casting mold to obtain an aluminum alloy round ingot.

3. The method for controlling impurity elements in aluminum melt recovery according to claim 1, wherein: The weight proportions of the raw materials in step 1) are as follows: 4 parts of graphene, 7.5 parts of calcium nitride, 3.3 parts of titanium dioxide, 1.6 parts of ammonium fluoroborate, 1.4 parts of zeolite powder, 0.5 parts of aluminum oxide, 0.2 parts of potassium sulfate, 5 parts of sodium tetraborate, and 0.2 parts of magnesium aluminum silicate.

4. The method for controlling the recovery of impurity elements in aluminum melt according to claim 1, wherein: In step 1), the ball milling time is 8-8.5 minutes, the rotation speed of the ductile iron is 3200-3500 rpm, and the ball-to-material ratio is 13:

1.

5. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 2), the filter material is in the form of a filter plate, and the thickness of the filter plate is 2 to 3 cm.

6. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 2), the mass fractions of brown corundum, the composite material, polyaluminum oxalate, and polyaluminum citrate are 83%, 7%, 7%, and 3% respectively; and the mass fraction of added water is 5.5%.

7. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 2), the stirring time in the wheel mill is 12 minutes; the drying time is 12-13 hours; and the green body material is fired at a temperature of 1220-1230° C. for 1.2 hours.

8. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 3), a graphite rotor is provided in the degassing box. The rotation speed of the graphite rotor is 800-1000 rpm, the mixed gas flow rate on the graphite rotor is 6-7 cubic meters / hour, and the mixed gas pressure is 0.8-1 MPa. The mixed gas is a mixed gas composed of argon with a purity of ≥99.9% and chlorine with a purity of ≥99.9%, wherein the volume percentage of chlorine is 20-30%.

9. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 3), the amount of the refining agent is 0.2% to 0.4% of the total weight of the aluminum melt.

10. The method for controlling impurity elements in aluminum melt recovery according to claim 1, characterized in that: In step 3), at least two stages of filter plates are provided in the filter box.

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