Manufacturing method of secondary aluminum metal block

Abstract

Provided is a method for efficiently producing a secondary aluminum metal block from aluminum scrap. This method for producing a secondary aluminum metal block comprises a step for irradiating aluminum metal containing aluminum scrap with microwaves.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a recycled aluminum metal block. Background Art

[0002] By reducing the weight of automotive components, fuel efficiency can be improved and power consumption can be reduced. Therefore, research is underway to replace conventionally used iron-based materials with aluminum-based materials.

[0003] The raw material of such aluminum-based materials, i.e., aluminum metal billets (ingots), can also be manufactured by refining from bauxite, the original ore, but refining requires a large amount of energy. Therefore, in recent years, attempts have been made to reuse aluminum scraps generated from ingots and products to manufacture aluminum ingots or products.

[0004] For example, Patent Document 1 describes a method for refining aluminum scraps, characterized in that the aluminum scraps are melted in a melting furnace, refined to remove impurity components contained in the melt, and then the melt is poured out and cast into ingots of a specified size. When remanufacturing aluminum ingots, the melting process of the above aluminum scraps is separated from the refining process, the refining process is connected to the casting process, and in the above melting furnace, only the melting of the above aluminum scraps is performed and the melt is poured into a ladle, and the ladle is covered with a lid made of a refractory material connected to an exhaust device, the atmosphere in the ladle is depressurized to a specified pressure and maintained for a specified time, volatile components are removed from the melt, and then the pressure is restored to atmospheric pressure, and the melt is continuously poured into a mold.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-108346. Summary of the Invention

[0008] The forms of aluminum scraps are roughly classified into processing scraps and waste scraps. Among the processing scraps, new aluminum chips mainly generated by stamping factories and chips generated by machine factories can be cited.

[0009] In order to reuse aluminum scraps of this form, it is necessary to perform pretreatment such as drying and compression molding to form them into lumps, and then melt them in an aluminum melt and cast them into aluminum ingots or products.

[0010] However, for example, in the case of chips, the proportion melted in the aluminum melt, that is, the melting yield, is about 20%, and even for lumps, the melting yield in the aluminum melt remains at about 40%. Therefore, efforts have been made to stir the melt and add chips and lumps into the gaps of the ingots to improve the melting efficiency.

[0011] In addition, when aluminum scrap is melted into molten aluminum, carbon dioxide (CO2) is generated during refining by raising the temperature of the molten metal and performing flux treatment, and CO2 causes global warming, so reduction is required.

[0012] Therefore, an object of the present invention is to provide a method for efficiently producing recycled aluminum metal blocks from aluminum scrap.

[0013] The inventors of the present invention conducted various studies on means for solving the above problems. As a result, it was found that by irradiating aluminum scrap with microwaves to produce recycled aluminum metal blocks, the present invention was completed.

[0014] That is, the gist of the present invention is as follows.

[0015] (1) A method for producing a recycled aluminum metal block, comprising a step of irradiating aluminum metal containing aluminum scrap with microwaves.

[0016] (2) The method according to (1), wherein the aluminum scrap is aluminum scrap in one or more forms selected from powder, chips, burrs, and lumps.

[0017] (3) The method according to (1) or (2), further comprising a step of compressing the aluminum metal.

[0018] (4) The method according to (3), wherein the step of compressing the aluminum metal is performed before, during, and / or after the irradiation of the microwaves.

[0019] (5) The method according to (3) or (4), wherein the step of compressing the aluminum metal is performed using a mold.

[0020] This specification includes the disclosure of Japanese Patent Application No. 2023-074519, which is the basis of the priority of the present application.

[0021] According to the present invention, there is provided a method for efficiently producing recycled aluminum metal blocks from aluminum scrap. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 are photographs of the appearance and interior of Comparative Example 1 and Example 1.

[0023] Figure 2 are photographs of the cross-sectional structures of Comparative Example 2 and Example 1.

[0024] Figure 3 are photographs showing the situation after melting of chips, Comparative Example 2, and Example 1.

[0025] Figure 4 is a table showing the results of a melting experiment of chips, Comparative Example 2, and Example 1 to become molten aluminum. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0027] In this specification, the features of the present invention are described with reference to appropriate drawings. It should be noted that the method for manufacturing the recycled aluminum metal block of the present invention is not limited to the following embodiments, and can be implemented in various ways obtained by making changes and improvements that can be made by those skilled in the art without departing from the gist of the present invention. In addition, in the present invention, the expression "numerical value (lower limit) to numerical value (upper limit)" represents a range including the lower limit and the upper limit.

[0028] The present invention relates to a method for manufacturing a recycled aluminum metal block, which includes a step of irradiating microwaves to aluminum metal containing aluminum scraps (a step of irradiating microwaves to aluminum metal).

[0029] In the present invention, the aluminum metal is a metal and / or alloy containing aluminum (Al) as a main component. In addition, the recycled aluminum metal block is a metal block and / or alloy block containing aluminum (Al) as a main component.

[0030] The aluminum metal contains aluminum scraps as an aluminum source (aluminum material).

[0031] Examples of the aluminum scraps include scraps generated in the manufacturing process of automotive aluminum components, materials recovered from chips, foils of higher-quality aluminum scraps, printing plates, 5000-series scraps (Al-Mg alloy), 6000-series scraps (Al-Mg-Si alloy), 7000-series scraps (Al-Zn-Mg alloy) (these include, for example, forged aluminum materials such as automotive and home appliance panel materials, radiators, and aircraft component materials). As the aluminum scraps, depending on the chemical composition of the aluminum scraps, not only one kind can be used, but also two or more kinds can be used. As the aluminum scraps, aluminum scraps with uncertain composition can also be used.

[0032] The aluminum scraps are, for example, one or more forms selected from powders, chips, burrs, agglomerates, etc. Here, the agglomerates are formed by compacting fine aluminum scraps such as chips and burrs. When the aluminum scraps are a mixture of two or more forms, the mixture can be homogeneous or heterogeneous. In one embodiment, the mixture is homogeneous.

[0033] The proportion of the aluminum scraps contained in the aluminum metal is not limited. The aluminum contained in the aluminum metal other than the aluminum scraps as the aluminum source can be pure aluminum ingots or metal blocks and / or aluminum alloys. The proportion of the aluminum scraps contained in the aluminum metal can be 100% by mass based on the total mass of the aluminum metal.

[0034] In the above aluminum metal, in addition to Al as the main component, other modifying alloying elements may also be appropriately further contained, such as one or more elements selected from boron (B), carbon (C), nitrogen (N), silicon (Si), magnesium (Mg), manganese (Mn), iron (Fe), copper (Cu), titanium (Ti), nickel (Ni), zirconium (Zr), cobalt (Co), molybdenum (Mo), tungsten (W), zinc (Zn), lithium (Li), silver (Ag), gallium (Ga), germanium (Ge), scandium (Sc), strontium (Sr), indium (In), vanadium (V), praseodymium (Pr), samarium (Sm), tantalum (Ta), gold (Au), beryllium (Be), chromium (Cr), arsenic (As), selenium (Se), yttrium (Y), niobium (Nb), ruthenium (Ru), rhodium (Rh), palladium (Pd), cadmium (Cd), tin (Sn), antimony (Sb), tellurium (Te), cerium (Ce), neodymium (Nd), promethium (Pm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), lutetium (Lu), hafnium (Hf), rhenium (Re), iridium (Ir), platinum (Pt), mercury (Hg), bismuth (Bi), and thorium (Th) (other elements).

[0035] The above other elements may also be added to the above aluminum metal in the form of the pure metal, compound, alloy, etc. of the element. It should be noted that, basically, metals with high melting points can be added as master alloys with other additive elements, and metals with low melting points can be added as pure metals. The addition of other elements can be carried out before, during, and / or after the irradiation of microwaves. Or, other elements may also be pre-included as alloy components in aluminum scraps and / or aluminum alloys in the aluminum metal.

[0036] It should be noted that "before, during, and / or after the irradiation of microwaves" means one or more moments among before, during, and after the irradiation of microwaves.

[0037] The content of each of the above other elements is not limited. For the content of each of these other elements, based on the total mass of the aluminum metal, it is generally 0.0001% by mass to 20% by mass in terms of metal, and in one embodiment, it is 0.001% by mass to 12% by mass. For the total content of these other elements, based on the total mass of the aluminum metal, it is generally 0.01% by mass to 30% by mass in terms of metal, in one embodiment, it is 0.01% by mass to 16% by mass, and in another embodiment, it is 0.01% by mass to 5% by mass. It should be noted that the content of these other elements can be measured by methods well-known in the art, and although it varies depending on the alloying element, for example, it can be measured by ICP emission spectrometry.

[0038] The remainder of the aluminum metal of the present invention, excluding aluminum and other elements, is inevitable impurities, organic substances such as coolant (cutting oil) and lubricating oil during aluminum product processing that may be contained in aluminum scrap, moisture, etc.

[0039] Here, as inevitable impurities, phosphorus (P) and sulfur (S) can be cited. The contents of phosphorus (P) and sulfur (S) are not limited. The content of each of phosphorus (P) and sulfur (S) is usually 0.01% by mass or less based on the total mass of the aluminum metal. It should be noted that the contents of phosphorus (P) and sulfur (S) can be measured by methods well-known in the art. Although it varies depending on the element to be measured, for example, it can be measured by ICP emission spectrometry.

[0040] In addition, the organic substances and moisture that may be contained in the aluminum scrap can be removed in advance. The removal of organic substances and moisture can use methods well-known in the art. For example, drying at 100°C to 600°C can be cited.

[0041] The size of the above-mentioned aluminum metal is not limited. In the above irradiation of the aluminum metal with microwaves, the aluminum metal and / or the microwave irradiation source can be moved so that the aluminum metal is irradiated with microwaves without omission.

[0042] The microwaves irradiated on the aluminum metal are not limited.

[0043] Microwaves are generated by a microwave irradiation source (microwave oscillator (magnetron)). The microwave irradiation source can use either a single-mode system or a multi-mode system.

[0044] The number of microwave irradiation sources is not limited. The number of microwave irradiation sources can be one or two or more.

[0045] The output of the microwave irradiation source is not limited. The output of the microwave irradiation source is usually 1 W to 10 kW, and in one embodiment, it is 500 W used in household applications to 10 kW used in industrial applications.

[0046] The frequency of the microwaves generated by the microwave irradiation source can be appropriately changed and is not limited. The frequency of the microwaves is usually 0.9 GHz to 10 GHz, and in one embodiment, it is 2 GHz to 6 GHz. In one embodiment, as the frequency of the microwaves, the frequency of an industrial microwave power supply, i.e., 2.45 GHz, is used.

[0047] The time for irradiating the aluminum metal with microwaves is not limited. The irradiation time of the microwaves can be appropriately changed according to the reaction conditions (composition, amount of the aluminum metal, microwave conditions, pressure, atmosphere, temperature, etc. during microwave irradiation). The irradiation time of the microwaves is usually 0.1 second to 600 seconds, and in one embodiment, it is 60 seconds to 300 seconds.

[0048] In one embodiment, the microwave is uniform during irradiation. In one embodiment, the irradiation conditions of the above-mentioned microwave are constant during the irradiation of the microwave.

[0049] In the present invention, by irradiating microwave to aluminum metal containing aluminum waste, recycled aluminum metal blocks can be manufactured, so that recycled aluminum metal blocks can be manufactured in a short time by utilizing the high-density energy of microwave.

[0050] The aluminum metal can also be compressed.

[0051] Therefore, the method for manufacturing the recycled aluminum metal block of the present invention may further include a step of compressing the above-mentioned aluminum metal (aluminum metal compression step).

[0052] The above-mentioned aluminum metal compression step is not limited. The above-mentioned aluminum metal compression step can be implemented by using techniques well known in the art. As the aluminum metal compression step, for example, uniaxial forming, cold isostatic pressing (CIP) forming, hot isostatic pressing (HIP) forming, and roll pressing can be cited.

[0053] In the above-mentioned aluminum metal compression step, for example, it can be implemented by using a mold plate. As the mold plate, a mold plate made of a metal such as aluminum or iron can be cited.

[0054] By using a mold plate in the above-mentioned aluminum metal compression step, it is particularly possible to prevent the scattering of fine aluminum waste, such as aluminum waste in the form of powder and debris, especially during the irradiation of microwave, that is, during heating. In addition, by using a mold plate in the shape of the product as the mold plate, the manufactured recycled aluminum metal block can be directly used as a product. It should be noted that, for example, the mixing of metal molds and processing tools that can be used as mold plates can be avoided by introducing a magnetic separation step.

[0055] In addition, the time of the above-mentioned aluminum metal compression step is not limited. Therefore, the aluminum metal compression step can be implemented before, during, and / or after the irradiation of the microwave. For example, by implementing the above-mentioned aluminum metal compression step before the irradiation of the microwave, an aluminum metal of appropriate size is prepared, and it is easy to introduce the aluminum metal into a mold plate that can be used during the irradiation of the microwave and the like. By implementing the above-mentioned aluminum metal compression step during and / or after the irradiation of the microwave, the density of the obtained recycled aluminum metal block can be further increased.

[0056] The pressure in the above-mentioned aluminum metal compression step is not limited. The pressure in the above-mentioned aluminum metal compression step is usually 10 MPa to 500 MPa.

[0057] The time in the above-mentioned aluminum metal compression step is not limited. The time in the above-mentioned aluminum metal compression step is until the aluminum metal is formed or shaped by the aluminum metal compression step. The time in the above-mentioned aluminum metal compression step is usually 0.1 second to 60 seconds, and in one embodiment, it is 2 seconds to 5 seconds.

[0058] The temperature in the compression process of the above aluminum metal is not restricted.

[0059] Since the manufacturing method of the recycled aluminum metal block of the present invention includes a compression process of aluminum metal, it is possible to remove organic substances and moisture that may be contained in aluminum waste by exudation (extraction) and separation, and it is possible to prevent the formation of bubbles due to gasification or the like in the finally obtained recycled aluminum metal block, thereby increasing the density of the aluminum metal block. Since the density of the recycled aluminum metal block manufactured by the manufacturing method of the present invention is high, when the aluminum metal block is melted and used, the melting yield can be increased.

[0060] The atmosphere in the manufacturing method of the recycled aluminum metal block of the present invention is not restricted. The manufacturing method of the recycled aluminum metal block of the present invention can be carried out in the atmosphere; an inert gas, such as argon (Ar) and / or helium (He); or a neutral gas, such as nitrogen (N2), dry hydrogen (dryH2) and / or ammonia (NH3).

[0061] In the manufacturing method of the recycled aluminum metal block of the present invention, particularly in the microwave irradiation process of aluminum metal, it can be carried out in a reducing atmosphere, such as an atmosphere containing hydrogen (H2), carbon monoxide (CO) and / or hydrocarbon gas (e.g., CH4, C3H8, C4H 10 )). Alternatively, in the manufacturing method of the recycled aluminum metal block of the present invention, particularly in the microwave irradiation process of aluminum metal, it can be carried out by disposing a reducing agent, such as carbon, near the aluminum metal, and for example, by mixing the aluminum metal and the reducing agent.

[0062] By carrying out the present invention in a reducing atmosphere or in the presence of a reducing agent, it is possible to prevent further oxidation of aluminum metal, particularly aluminum waste, or to reduce oxidized aluminum metal to metallic aluminum, thereby reducing the proportion of oxides in the obtained recycled aluminum metal block. Therefore, in the recycled aluminum metal block thus obtained, when the aluminum metal block is melted and used, it is possible to reduce the generation amount of slag and molten slag during melting and increase the melting yield.

[0063] In the manufacturing method of the recycled aluminum metal block of the present invention, it is not necessarily required to prepare molten aluminum, which is usually carried out when manufacturing the recycled aluminum metal block. Therefore, from the viewpoint of life cycle assessment (LCA), it is possible to reduce the amount of CO2 generated.

[0064] The density of the recycled aluminum metal block manufactured by the present invention can be adjusted as needed. For example, the recycled aluminum metal block manufactured by the present invention can be made to have a high density, and its density is usually 2.00 g / cm 3 ~the true density of aluminum metal (e.g., 2.70 g / cm for metallic aluminum) 3)。Alternatively, when the density of the recycled aluminum metal block produced by the present invention is set to 100% assuming that the recycled aluminum metal block is entirely metal or alloy, it can generally be 99% or more.

[0065] Therefore, when the recycled aluminum metal block produced by the present invention is used for melting, the melting yield can be improved. In addition, the recycled aluminum metal block produced by the present invention can be directly used as products such as components, or can be processed into products such as components by performing machining such as cutting. Additionally, the high-density recycled aluminum metal block produced by the present invention can be used in the same manner as ordinary aluminum ingots.

[0066] When the recycled aluminum metal block produced by the present invention contains Si as other elements, the internal structure is composed of granular Si phase and eutectic of aluminum. This is because the recycled aluminum metal block produced by the present invention is formed in a short time, and dendrites are not formed (present) in the internal structure. In addition, there are boundaries in the internal structure of the recycled aluminum metal block produced by the present invention. It should be noted that there are also voids in the internal structure of the recycled aluminum metal block produced by the present invention. However, the recycled aluminum metal block produced by the present invention can also achieve a high density, and its density can reach the above range, so the volume of the voids can be reduced.

[0067] Examples

[0068] Hereinafter, some examples related to the present invention will be described, but the present invention is not intended to be limited to the content shown in these examples.

[0069] I. Sample Preparation

[0070] Example 1

[0071] Using a silicon nitride mold, under an argon atmosphere, pressure of 5 MPa was applied to aluminum scraps (Cu: 1.5 mass% to 3.5 mass%, Si: 9.6 mass% to 12 mass%, Mg: 0.3 mass% or less, Zn: 1.0 mass% or less, Fe: 1.3 mass% or less, Mn: 0.5 mass% or less, Ni: 0.5 mass% or less, Sn: 0.2 mass% or less, Pb: 0.2 mass% or less, Ti: 0.3 mass% or less, Al: the balance) as aluminum waste, and at the same time, microwave was irradiated at 1 kW to produce the recycled aluminum metal block of Example 1.

[0072] Comparative Example 1

[0073] In an argon atmosphere, aluminum chips (Cu: 1.5% to 3.5% by mass, Si: 9.6% to 12% by mass, Mg: 0.3% or less by mass, Zn: 1.0% or less by mass, Fe: 1.3% or less by mass, Mn: 0.5% or less by mass, Ni: 0.5% or less by mass, Sn: 0.2% or less by mass, Pb: 0.2% or less by mass, Ti: 0.3% or less by mass, Al: the balance) as aluminum waste were compressed at a pressure of 5 MPa to produce the briquette of Comparative Example 1.

[0074] Comparative Example 2

[0075] As Comparative Example 2, an aluminum ingot (ADC12, cuttings, Cu: 1.5% to 3.5% by mass, Si: 9.6% to 12% by mass, Mg: 0.3% or less by mass, Zn: 1.0% or less by mass, Fe: 1.3% or less by mass, Mn: 0.5% or less by mass, Ni: 0.5% or less by mass, Sn: 0.2% or less by mass, Pb: 0.2% or less by mass, Ti: 0.3% or less by mass, Al: the balance) was prepared.

[0076] II. Evaluation

[0077] (Appearance and internal observation)

[0078] The appearance of the briquette of Comparative Example 1 and the recycled aluminum ingot of Example 1 were observed externally and internally using an optical microscope. The results are shown in Figure 1 .

[0079] According to Figure 1 , there were voids inside the appearance of the briquette of Comparative Example 1 and the density was low. On the other hand, the appearance of the recycled aluminum ingot of Example 1 had a metallic luster like that of metallic aluminum, and in addition, it was confirmed to have a high density based on the internal observation.

[0080] (Cross-sectional microstructure observation)

[0081] The cross-sectional microstructures of the aluminum ingot of Comparative Example 2 and the recycled aluminum ingot of Example 1 were observed using an optical microscope. The results are shown in Figure 2 .

[0082] According to Figure 2 the following was found.

[0083] In the aluminum ingot of Comparative Example 2, the internal structure was composed of a eutectic of acicular Si phase and aluminum, and dendrites were formed in the internal structure.

[0084] On the other hand, the internal structure of the recycled aluminum metal block of Example 1 is composed of a eutectic of granular Si phase and aluminum, and dendrites are not formed in the internal structure. In addition, in the internal structure of the recycled aluminum metal block of Example 1, there is a clear boundary compared with the aluminum ingot of Comparative Example 2, and there are also voids. However, the recycled aluminum metal block of Example 1 has a high density. When the aluminum metal block is completely metal (alloy) and set to 100%, its density is 99% or more. Therefore, the volume of the voids is small.

[0085] That is, the aluminum ingot of Comparative Example 2 generates dendrites by slow solidification when the melted metal is added to the mold for forming, while the recycled aluminum metal block of Example 1 is formed in a short time by microwave irradiation, so dendrites are not formed.

[0086] In addition, in Example 1, melting is not required during the manufacturing process, the metal block can be manufactured on-site on the spot, and oxidation of the attached coolant can be prevented. Therefore, Example 1 can reduce CO2 from the perspective of LCA.

[0087] It should be noted that when using aluminum alloy as aluminum scrap, compared with the aluminum alloy with a large amount of impurities in the alloy composition, the aluminum alloy with a practical alloy composition like A6061 with less impurities has a tendency for the boundary to become thinner.

[0088] (In-furnace melting test)

[0089] Approximately 28 g of each of the debris, the aluminum ingot of Comparative Example 2, and the recycled aluminum metal block of Example 1 were added to a furnace at a temperature of 800 °C and melted for about 30 minutes, and the gas and oxidation conditions in the furnace were confirmed. The results are shown in Figure 3 。

[0090] It can be seen from Figure 3 that there are also many oxides in the debris during melting, and the melting yield is very poor. Compared with the aluminum ingot of Comparative Example 2, the recycled aluminum metal block of Example 1 has slightly more oxides, but no gas is generated.

[0091] (Melting test in aluminum melt)

[0092] Approximately 28 g of each of the debris, the aluminum ingot of Comparative Example 2, and the recycled aluminum metal block of Example 1 were melted in the aluminum melt. The results are shown in Figure 4 。

[0093] It can be seen from Figure 4 that the debris floats on the melt, and the melting yield is less than 40%. However, the melting yield of the recycled aluminum metal block of Example 1 is increased to 60% or more.

[0094] All publications, patents, and patent applications cited in this specification are hereby incorporated by reference directly into this specification.

Claims

1. A method for producing a recycled aluminum metal block, comprising the step of irradiating aluminum metal containing aluminum scrap with microwaves.

2. The method according to claim 1, wherein: The aluminum scrap is aluminum scrap in one or more forms selected from the group consisting of powder, chips, burrs, and agglomerates.

3. The method according to claim 1 or 2, wherein: Further comprising the step of compressing the aluminum metal.

4. The method according to claim 3, wherein: The step of compressing the aluminum metal is performed before, during, and / or after the irradiation with microwaves.

5. The method according to claim 3, wherein: The process of compressing aluminum metal is carried out using a template.

6. The method according to claim 4, wherein: The process of compressing aluminum metal is carried out using a template.

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