Method for recycling aluminum alloy substrate, method for manufacturing magnetic disk, magnetic disk, and hard disk drive

Abstract

To provide a recycling method for an aluminum alloy substrate having superior recyclability.SOLUTION: This recycling method for an aluminum alloy substrate comprises: a film removal step of removing a film from a recycled material, which has an aluminum alloy substrate and at least one film layer on the aluminum alloy substrate, to provide an aluminum alloy material; a step of preparing molten aluminum alloy by using the aluminum alloy material as at least part of the feedstock; a step of heating and retaining the prepared molten metal; and a step of casting the heat-retained molten metal to provide an aluminum alloy ingot.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for recycling an aluminum alloy substrate, a method for manufacturing a magnetic disk, a magnetic disk, and a hard disk drive.

Background Art

[0002] Hard disk drives (HDDs) are widely used as storage devices in various electronic devices such as computers and data centers. In an HDD, a magnetic disk is responsible for storing information, and an aluminum alloy substrate for magnetic disks is used as the substrate of the magnetic disk. The aluminum alloy substrate for magnetic disks has good plating properties and excellent mechanical properties and workability. An aluminum alloy substrate according to JIS 5086 (3.5% by mass or more and 4.5% by mass or less of Mg, 0.50% by mass or less of Fe, 0.40% by mass or less of Si, 0.20% by mass or more and 0.70% by mass or less of Mn, 0.05% by mass or more and 0.25% by mass or less of Cr, 0.10% by mass or less of Cu, 0.15% by mass or less of Ti, 0.25% by mass or less of Zn, the balance being Al and inevitable impurities) is used. In one example, it is manufactured through a process of performing electroless Ni-P plating treatment on the aluminum alloy substrate and then polishing the surface smoothly. )

[0003] For example, an aluminum alloy substrate for magnetic disks using the JIS 5086 alloy is manufactured through the following manufacturing process. First, an aluminum alloy with a desired chemical composition is cast, the ingot is homogenized, then hot-rolled, and then cold-rolled to produce an aluminum alloy plate with the thickness required for a magnetic disk. This aluminum alloy plate is cold-rolled as necessary. ​​​​​​​​​​​​It is preferable to perform annealing during the intermediate rolling process. Next, this aluminum alloy plate is punched into an annular shape to form an annular disk blank, and in order to remove distortions and the like generated during the manufacturing process, the annular disk blanks are stacked, and annealing is performed while applying pressure from both sides to flatten them by pressure annealing. The annular disk blank thus produced is subjected to cutting processing, grinding processing, degreasing processing, etching processing, and zincate processing (Zn substitution processing) as preprocessing, and then Ni-P electroless plating processing, which is a hard non-magnetic metal, is performed as a base treatment, and the surface subjected to the Ni-P plating treatment is polished to manufacture an aluminum alloy substrate for a magnetic disk. and the like. Next, the annular disk blanks are stacked, and annealing is performed while applying pressure from both sides to flatten them by pressure annealing. The annular disk blank thus produced is subjected to cutting processing, grinding processing, degreasing processing, etching processing, and zincate processing (Zn substitution processing) as preprocessing, and then Ni-P electroless plating processing, which is a hard non-magnetic metal, is performed as a base treatment, and the surface subjected to the Ni-P plating treatment is polished to manufacture an aluminum alloy substrate for a magnetic disk. Next, Ni-P electroless plating processing, which is a hard non-magnetic metal, is performed as a base treatment, and the surface subjected to the Ni-P plating treatment is polished to manufacture an aluminum alloy substrate for a magnetic disk.

[0004] In recent years, with the development of cloud services, the construction of new data centers and the replacement of existing data centers with large-capacity HDDs have been actively promoted. Under such current circumstances, increasing the capacity of HDDs has become essential. To increase the capacity of HDDs, it is important to increase the number of magnetic disks installed and the capacity per magnetic disk. In the former case, it is necessary to reduce the thickness of the magnetic disk, and in the latter case, it is necessary to reduce the defects on the Ni-P plated surface of the aluminum alloy substrate for the magnetic disk. Although both of the above methods are technically possible, performing both of the above methods will result in poor yield in the manufacturing process of the magnetic disk. Specifically, when the magnetic disk is made thinner in the former case, higher processing accuracy will be required for rolling, grinding, etc., and for the defects on the Ni-P surface in the latter case, the threshold value for the number of occurrences will become stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products will increase, and considering the future demand for magnetic disks, the construction of new data centers and the replacement of existing data centers with large-capacity HDDs have been actively promoted. Under such current circumstances, increasing the capacity of HDDs has become essential. To increase the capacity of HDDs, it is important to increase the number of magnetic disks installed and the capacity per magnetic disk. In the former case, it is necessary to reduce the thickness of the magnetic disk, and in the latter case, it is necessary to reduce the defects on the Ni-P plated surface of the aluminum alloy substrate for the magnetic disk. In the former case, it is necessary to reduce the thickness of the magnetic disk, and in the latter case, it is necessary to reduce the defects on the Ni-P plated surface of the aluminum alloy substrate for the magnetic disk. Although both of the above methods are technically possible, performing both of the above methods will result in poor yield in the manufacturing process of the magnetic disk. Specifically, when the magnetic disk is made thinner in the former case, higher processing accuracy will be required for rolling, grinding, etc., and for the defects on the Ni-P surface in the latter case, the threshold value for the number of occurrences will become stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products will increase, and considering the future demand for magnetic disks, when the magnetic disk is made thinner, higher processing accuracy will be required for rolling, grinding, etc., and for the defects on the Ni-P surface, the threshold value for the number of occurrences will become stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products will increase, and considering the future demand for magnetic disks, ​It is easy to predict that the number of defective aluminum alloy substrates will increase.

[0005] In recent years, due to the increasing interest in environmental protection, it has become essential to establish recycling technologies for metal products. In addition, geopolitical risks associated with different types of metals have become apparent. Although aluminum is a relatively easy metal to recycle, the recyclability varies depending on its alloy system. For example, in the case of aluminum can materials, the same alloy can be collected and used as raw material, so it can be easily made into aluminum can materials again. However, the aluminum clad material used for heat exchanger materials has a multi-layer structure of aluminum alloys with different compositions, and it is impossible to separate each layer. Therefore, it is necessary to remelt and cast the entire aluminum clad material, but since it changes from the original alloy composition during remelting and casting, the range of use of the recycled product may be limited.

[0006] On the other hand, aluminum alloys for magnetic disks are high-cost materials that use a large amount of high-purity ingots for improving plating defects and limit the content of Fe, Si, etc. Therefore, by recycling as much as possible, it is possible to reduce the amount of high-purity ingots used. This can reduce the amount of high-purity ingots produced and contribute to environmental protection to some extent.

[0007] In the manufacturing process of aluminum alloy substrates for magnetic disks, if they do not meet the predetermined standards due to rolling, grinding, etc. and become defective products, they can be reused as part of the raw material as they are. However, for aluminum alloy substrates for magnetic disks with a film such as an Ni-P plating layer formed on the surface, If it becomes a defective product in the state of the alloy substrate, its recycling becomes complicated. That is, for the aluminum alloy substrate for magnetic disks, a film such as an Ni-P plating layer is applied. Therefore, for example, it can be used as a casting alloy such as the housing of an HDD. On the other hand, as described above, simply recycling an aluminum alloy using a large amount of high-purity metal as a casting is not good in terms of recycling efficiency. Therefore, it has been desired to reuse the defective aluminum alloy substrate for magnetic disks as a rolled material, preferably as an aluminum alloy material for magnetic disks again.

[0008] Against such a background, the establishment of a technique for separating a film such as an Ni-P plating layer from an aluminum alloy and recovering the aluminum alloy substrate is demanded.

[0009] For example, Patent Document 1 discloses a method of recycling an aluminum alloy substrate with an Ni-P plating layer as a raw material for an Al-Si alloy. Although this technique enables the recycling of the aluminum alloy substrate, it has been difficult to efficiently use the aluminum alloy substrate using high-purity metal.

[0010] Patent Document 2 discloses a method of returning the substrate after removing the Ni-P plating layer to the plating process again for recycling. With this technique, the recycled aluminum alloy substrate can be reused. However, recently, the requirements for defects in the Ni-P plating layer of the aluminum alloy substrate for magnetic disks have become extremely strict. Therefore, if the aluminum alloy substrate from which a film such as an Ni-P plating layer has been peeled is reused as it is, it will be in a state where the surface has been damaged. Since the aluminum alloy substrate is subjected to plating treatment, there is a possibility that defects on the plating surface occur frequently. There were.

[0011] As described above, in the prior art, it is impossible to reuse the aluminum alloy substrate while maintaining high quality, and it has been difficult to reuse the aluminum alloy substrate for magnetic disks and the like that require high quality in recent years. For alloy substrates.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention has been made in view of the above circumstances, and an object thereof is to provide a recycling method for an aluminum alloy substrate having excellent recyclability.

Means for Solving the Problems

[0014] The inventors of the present invention use, as at least part of the raw materials, an aluminum alloy material obtained by removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film, and perform preparation, heating and holding, and casting of the molten metal, thereby achieving a desired alloy composition and obtaining an aluminum alloy plate with few defects. The present invention has been completed based on this finding. For the molten metal. and arrived.

[0015] The recycling method for an aluminum alloy substrate according to an embodiment of the present invention is ​Having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate A film removal step of removing the film from the recyclable material having the film to obtain an aluminum alloy material A step of preparing molten aluminum alloy using the aluminum alloy material as at least part of the raw material A step of preparing the molten metal A step of heating and holding the prepared molten metal A step of casting the heated and held molten metal to obtain an aluminum alloy ingot It has

Advantages of the Invention

[0016] According to the present invention, a recycling method for an aluminum alloy substrate excellent in recyclability can be provided It can be

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail

[0018] 1. Recycling method for aluminum alloy substrate The recycling method for an aluminum alloy substrate in the present invention is (a) A film removal step of removing the film from the recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material (b) A step of preparing molten aluminum alloy using the aluminum alloy material as at least part of the raw material (c) A step of heating and holding the prepared molten metal (d) A step of casting the heated and held molten metal to obtain an aluminum alloy ingot (e) It has (f) In the recycling method of the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by removing the film from the recyclable material in the film removal step is used as at least part of the raw material It has In the recycling method of the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by removing the film from the recyclable material in the film removal step is used as at least part of the raw material The aluminum alloy material obtained by removing the film from the recyclable material in the film removal step is used as at least part of the raw material is used as a material to prepare a molten aluminum alloy, heat and hold the molten metal, and produce an aluminum alloy ingot. In the prior art, an aluminum alloy substrate with the coating removed was recycled as it was, and a coating such as a Ni-P plating layer was formed on the aluminum alloy substrate. As a result, defects sometimes occurred on the coating. In contrast, in the method for recycling an aluminum alloy substrate of the present invention, the coating can be effectively removed from the recycled material in the coating removal step. After removing the coating, the obtained aluminum alloy material is used as it is to prepare a molten aluminum alloy and perform subsequent steps, thereby producing an aluminum alloy ingot while maintaining the alloy composition of the aluminum alloy material. In addition, when preparing the molten aluminum alloy, by adding an arbitrary material, element, aluminum alloy base metal, etc. to the molten metal, an aluminum alloy ingot with a desired alloy composition can be produced. Consequently, the present invention can provide a method for recycling an aluminum alloy substrate with excellent recyclability. Moreover, since the amount of expensive high-purity aluminum base metal used can be reduced without degrading performance, cost reduction can be achieved. In one aspect, by setting the conditions for heating and holding the molten metal, producing an aluminum alloy ingot from the molten metal, homogenizing the aluminum alloy ingot, and rolling the aluminum alloy ingot to predetermined conditions, the properties and characteristics of the rolled aluminum alloy sheet can be set to desired properties and characteristics different from those of the recycled material. Furthermore, in one aspect, since the rolled aluminum alloy sheet can have few surface defects, when forming a coating on the aluminum alloy sheet, the defects of the coating can also be reduced.

[0019] (Recycled material) The "recycled material" used in the present invention is a material having an aluminum alloy substrate and a film on the aluminum alloy substrate. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Examples of the recycled material include intermediate materials and finished products generated in the manufacturing process of magnetic disks. The "intermediate material" corresponds to, for example, an aluminum alloy substrate for magnetic disks, and the "finished product" corresponds to, for example, a magnetic disk. These recycled materials include defective products, out-of-specification products, and used magnetic disks, etc. Also, the "film" is not particularly limited as long as it is one or more layers formed on the aluminum alloy substrate, and examples thereof include Ni-P plating layers, magnetic layers, protective layers, lubricating layers, etc. The shape of the recycled material is not particularly limited and may be an annular shape, a polygonal shape, or an irregular shape having no specific shape. Many of the recycled materials are annular, and it is easy to procure annular recycled materials. For this reason, the aluminum alloy substrate constituting the recycled material is preferably annular. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. In the method for recycling the aluminum alloy substrate of the present invention, the aluminum alloy material obtained by the film removal process is used as at least part of the raw material, and only the aluminum alloy material may be used as the raw material, or other materials and elements may be used as the raw material together with the aluminum alloy material. Hereinafter, the intermediate material and the finished product will be described in more detail.

[0020] (Intermediate material) Examples of the intermediate material include aluminum alloy substrates for magnetic disks generated in the manufacturing process of magnetic disks. In one example, the surface of the aluminum alloy substrate for magnetic disks Examples of the intermediate material include aluminum alloy substrates for magnetic disks generated in the manufacturing process of magnetic disks. In one example, the surface of the aluminum alloy substrate for magnetic disks A film containing Ni such as an Ni-P plating layer is formed. For an aluminum alloy substrate for a magnetic disk, the Ni content in the film containing Ni used is, for example, 80% by mass or more and 95% by mass or less. When the film containing Ni is an Ni-P plating layer, the P content contained in the Ni-P plating layer is, for example, 5% by mass or more and 20% by mass or less. Also , the thickness of the film containing Ni is not particularly limited, but for example, it is 3 μm or more and 25 μm or less . In this case, the thickness of the aluminum alloy substrate for a magnetic disk is, for example, 0.3 mm or more and 2.0 mm or less.

[0021] (Finished product) Examples of the finished product include a magnetic disk. In an example of a magnetic disk, as a film on the surface of the aluminum alloy substrate for a magnetic disk, an Ni-P plating layer, a CoCrPt-based magnetic layer, a protective layer such as a carbon-based material, etc. are formed in this order. Since these magnetic layers and protective layers are formed on the Ni-P plating layer, by removing the Ni-P plating layer, these magnetic layers and protective layers can also be removed. Therefore, the aluminum alloy material obtained by removing the film from the finished product magnetic disk can also be used as at least part of the raw material .

[0022] 2. Each step of the recycling method of the aluminum alloy substrate As described above, the recycling method of the aluminum alloy substrate of the present invention has steps (a) to (d) . Hereinafter, each of steps (a) to (d) will be described in detail.

[0023] (a) Film removal step In the film removal step, the film is removed from the recycled material. As a treatment method for removing the film Although not particularly limited, treatment methods such as chemical treatment, physical treatment, and heat treatment can be mentioned. In the film removal step, it is preferable to perform chemical treatment, and it is more preferable to remove the film from the recycled material by immersing the recycled material in a solution. As an example of the recycled material, it has a Ni-P plating layer as a film on an aluminum alloy substrate, and the Ni-P plating layer is formed on all surfaces of both sides, inner diameter, and outer diameter of the aluminum alloy substrate. By immersing the recycled material in a solution, the Ni-P plating layer formed as a film on all such surfaces can be effectively removed. Also, the solution is preferably an acidic solution containing nitrate ions. By immersing the recycled material in an acidic solution containing nitrate ions, the film such as the Ni-P plating layer can be efficiently removed. Also, since the aluminum alloy substrate has corrosion resistance against an acidic solution containing nitrate ions, the aluminum alloy substrate does not dissolve in the acidic solution. As a result, a high-quality aluminum alloy plate can be obtained. Also, when a recycled material having a film such as a Ni-P plating layer is immersed in an alkaline solution, since the Ni-P plating layer has corrosion resistance against the alkaline solution, the dissolution of the Ni-P plating layer does not progress, and it may be difficult to remove the film such as the Ni-P plating layer. In contrast, by immersing the recycled material in an acidic solution containing nitrate ions, such a situation can be prevented. The acidic solution can be prepared by dissolving nitric acid or nitrates such as sodium nitrate and potassium nitrate in a solvent such as pure water, industrial water, or tap water, but an aqueous nitric acid solution is preferred. When a recycled material having a film such as a Ni-P plating layer is immersed in an alkaline solution, since the Ni-P plating layer has corrosion resistance against the alkaline solution, the dissolution of the Ni-P plating layer does not progress, and it may be difficult to remove the film such as the Ni-P plating layer. In contrast, by immersing the recycled material in an acidic solution containing nitrate ions, such a situation can be prevented.

[0024] The acidic solution can be prepared by dissolving nitric acid or nitrates such as sodium nitrate and potassium nitrate in a solvent such as pure water, industrial water, or tap water, but an aqueous nitric acid solution is preferred. Preferred. However, when using nitrates, it is necessary to further add nitric acid or hydrochloric acid to make an acidic solution. Alternatively, commercially available aqueous nitric acid can also be used. The nitrate ion concentration in the acidic solution is preferably 5% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more. Also, the nitrate ion concentration in the acidic solution is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. By having the nitrate ion concentration in the acidic solution within the above range, the film can be efficiently removed in a short time. In the acidic solution, anions such as chloride ions, sulfate ions, and phosphate ions may be present as anions other than nitrate ions. The total concentration of anions other than nitrate ions in the acidic solution is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. By having the total concentration of anions other than nitrate ions in the acidic solution within the above range, anions other than nitrate ions do not affect the action of removing the nitrate ion film, and the film can be efficiently removed. Also, the pH of the acidic solution is preferably -1 to 4, more preferably -1 to 3, and even more preferably -1 to 2. By having the pH of the acidic solution within the above range, the film can be efficiently removed. As conditions for immersing the recycled material in the acidic solution, it can be set to a suitable temperature of the acidic solution and a suitable immersion time according to the characteristics of the recycled material. The acidic solution preferably has a temperature of 40 to 60 °C, more preferably 45 to 60 °C, and 5 As for the conditions for immersing the recycled material in the acidic solution, it can be set to a suitable temperature of the acidic solution and a suitable immersion time according to the characteristics of the recycled material. The acidic solution preferably has a temperature of 40 to 60 °C, more preferably 45 to 60 °C, and 5

[0025] °C is even more preferably. The immersion time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes, and even more preferably 10 to 20 minutes. °C is even more preferably. The immersion time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes, and even more preferably 10 to 20 minutes. °C is even more preferably. The immersion time is preferably 1 to 60 minutes, more preferably 5 to 30 minutes, and even more preferably 10 to 20 minutes. It is more preferable to have a temperature of 0 to 60°C. When the temperature of the acidic solution is within the above range, the film can be efficiently removed in a short time and the generation of gas due to the decomposition of nitric acid can be prevented. The time for immersing the recycled material in the acidic solution is preferably 1 hour or more, more preferably 1 to 3 hours, and even more preferably 1.5 to 2 hours. When the time for immersing the recycled material in the acidic solution is within the above range, the film can be efficiently removed without leaving any residue. The film removal rate depends on the conditions of the film removal process. In one example, the film removal rate is 4 to 7 μm of film removal in 30 minutes. On the other hand, the thickness of the film on the annular recycled material is, for example, 5 to 10 μm on the surface, and 7 to 12 μm for the inner and outer diameters. Therefore, in the above example, by immersing the recycled material in the acidic solution for 1 hour or more, the films on both sides of the aluminum alloy substrate, the entire inner and outer diameters can be effectively and surely removed. In the film removal process, one or more recycled materials can be immersed in the solution. When one recycled material is immersed in the solution, the film can be removed from the recycled material in a short time. When multiple recycled materials are immersed in the solution, more recycled materials can be processed at once because the film can be removed from multiple recycled materials at the same time. When multiple recycled materials are immersed in the solution, it is preferable to arrange them in the solution so that they do not contact each other. By arranging multiple recycled materials in this way, it becomes difficult for the solution to penetrate into the contact parts of each recycled material. μm, 7 to 12 μm for the inner and outer diameters. Therefore, in the above example, by immersing the recycled material in the acidic solution for 1 hour or more, the films on both sides of the aluminum alloy substrate, the entire inner and outer diameters can be effectively and surely removed.

[0026] In the film removal process, one or more recycled materials can be immersed in the solution. When one recycled material is immersed in the solution, the film can be removed from the recycled material in a short time. When multiple recycled materials are immersed in the solution, more recycled materials can be processed at once because the film can be removed from multiple recycled materials at the same time. When multiple recycled materials are immersed in the solution, it is preferable to arrange them in the solution so that they do not contact each other. By arranging multiple recycled materials in this way, it becomes difficult for the solution to penetrate into the contact parts of each recycled material. It is possible to prevent the film that has not been partially removed from remaining. Also, the film is removed and aluminum In the recycled material where the aluminum alloy is exposed, the aluminum alloy and the film in the recycled material where the film has not been removed come into contact with each other to form a dissimilar metal contact state, and it is possible to prevent the removal of the film from progressing Note that the distance between each recycled material in the solution is not particularly limited and can be set to a desired distance according to the size of the container that holds the solution, the number and size of the recycled materials immersed in the solution, etc.

[0027] (b) Step of preparing a molten aluminum alloy Next, a molten aluminum alloy is prepared using at least a part of the aluminum alloy material obtained in the film removal step as a raw material. The content of each element in the molten metal prepared in step (b) is described below.

[0028] · Ni (nickel) content The Ni content in the molten aluminum alloy is preferably 0% by mass or more and 2.5% by mass or less. Ni combines with aluminum (Al) etc. to form an Al-Ni based compound, which generates large defects on the plating surface. Therefore, it is useful to reduce the Ni content. The Ni content in the molten metal is preferably 2.5% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. The adjustment of the Ni content is carried out in the step of preparing the molten aluminum alloy by heating and melting the raw materials. For example, after the raw materials in the molten metal are completely melted, the components of the molten metal are analyzed. When the Ni content is high, aluminum alloy ingots etc. are added to adjust to the desired Ni content.

[0029] · P (phosphorus) content ​​​​​​​The P content in the molten aluminum alloy should be 0 mass% or more and 0.05 mass% or less. This is preferable. P is contained in aluminum alloy ingots and the like, but it combines with Mg (magnesium) generally contained in the molten metal raw material aluminum alloy to form Mg-P-based oxides, and during the plating process, the reaction becomes non-uniform only in that part, resulting in large defects on the plating surface. As a result, the smoothness of the plating surface decreases. Some of the Mg-P-based oxides can float to the surface of the molten metal and be removed by heating and holding the molten metal, but it is preferable that the content of P itself that combines with Mg is low. The P content in the molten metal is preferably 0.05 mass% or less, and more preferably 0.01 mass% or less. Since the P content in the molten metal is very small compared to the Ni content, it is generally not necessary to add aluminum alloy ingots or the like to adjust to the desired content. However, when adjustment is necessary, similar to Ni, aluminum ingots or the like are added to adjust to the desired content.

[0030] ·Mg (magnesium) content The Mg content in the molten aluminum alloy should be 0 mass% or more and 6.5 mass% or less. As described above, since Mg combines with P in the molten metal to form Mg-P-based oxides, it is preferable that its content is low, similar to P. The Mg content in the molten metal is preferably 6.5 mass% or less, and more preferably 4.5 mass% or less. When the Mg content is high, similar to Ni, aluminum alloy ingots or the like are added to adjust to the desired content.

[0031] ·Metal components in the molten aluminum alloy Regarding the metal components contained in the molten aluminum alloy, as described above, Ni, P and its content, and elements such as Cu and Mg that form intermetallic compounds with P are adjusted preferably.

[0032] On the other hand, elements other than Ni, P, Cu and Mg and their contents are not particularly limited. As the alloy composition contained in the molten aluminum alloy, for example, the following can be mentioned. The aluminum alloy contains Fe (iron) and optionally Mn (manganese), and the total content of these Fe and Mn is in the range of 0.005% by mass or more and 7.00% by mass or less. Furthermore, it contains 0.5% by mass or more and 6.5% by mass or less of Mg, and optionally, 0% by mass or more and 1.0% by mass or less of Si (silicon), 0% by mass or more and 0.7% by mass or less of Zn (zinc) , 0% by mass or more and 0.30% by mass or less of Cr (chromium), and 0% by mass or more and 0.20% by mass or less of Zr (zirconia), and contains one or more metals selected from the group consisting of, and the balance is composed of Al and inevitable impurities and other trace components.

[0033] Examples of inevitable impurities include Ti (titanium) and Ga (gallium) contained in the aluminum alloy. Examples of other trace components include Co (cobalt) and Pt (platinum). The contents of these inevitable impurities and other trace components are 0.10% by mass or less for each element and 0.30% by mass or less in total, which will not impair the effects of the present invention.

[0034] (c) Step of heating and holding the molten metal Next, the molten aluminum alloy is heated and held. In this step, the molten aluminum alloy is heated and held by a holding furnace. At this time, the oxide film floating on the surface of the molten metal is removed outside the furnace. It is preferable to skim off this floating oxide film before casting the aluminum alloy. By removing it by means such as skimming, the contents of Ni and P in the molten metal can be reduced. It is preferable to remove the oxide film outside the furnace as quickly as possible.

[0035] (d) Step of casting the molten metal to obtain an aluminum alloy ingot Next, the molten metal is cast to obtain an aluminum alloy ingot. The molten aluminum alloy held by heating is, if necessary, after the in-line degassing treatment and in-line filtration treatment described later, and then semi-continuous casting method (DC casting method), die casting method, continuous casting method (CC method), etc. to cast the aluminum alloy into an ingot. In the DC casting method, the molten metal poured through the spout is directly discharged onto the bottom block, the wall of the water-cooled mold, and the outer periphery of the ingot (ingot), and the heat is taken away by the cooling water sprayed, solidified, and pulled downward as an ingot. In the die casting method the molten metal poured into a hollow mold made of cast iron or the like has its heat taken away by the mold wall and solidifies to produce an ingot. In the CC casting method, the molten metal is supplied through a casting nozzle between a pair of rolls (or a belt caster, block caster), and a thin plate is directly cast by heat extraction from the rolls. .

[0036] The molten metal held in the step of heating and holding the molten metal is preferably subjected to in-line degassing treatment and in-line filtration treatment according to a conventional method before being subjected to the casting process. As the in-line degassing treatment device, commercially available degassing devices under trademarks such as SNIF and ALPUR can be used. These in-line degassing treatment devices rotate a rotor with blades at high speed while blowing argon gas or a mixed gas of argon and nitrogen into the molten metal to make the gas into fine bubbles. ​​​and supplied into the molten metal. As a result, dehydrogenated gas and inclusions can be removed inline in a short time. As the inline filtration process, a ceramic tube filter, a ceramic foam filter, an alumina ball filter, etc. are used, and inclusions are removed by a cake filter structure, a filter medium filtration mechanism, etc.

[0037] 3. Method for manufacturing a magnetic disk The method for manufacturing a magnetic disk of the present invention includes (e) a step of heating the aluminum alloy ingot obtained by the recycling method of the aluminum alloy substrate and performing a homogenization treatment; and (f) a rolling step of rolling the homogenized aluminum alloy ingot into an aluminum alloy plate; and (g) a step of pressurizing and flattening the aluminum alloy plate obtained by the rolling step into an annular disk blank; and (h) a step of subjecting the pressurized and flattened annular disk blank to cutting and grinding to obtain an aluminum alloy substrate for plating; and (i) a pre-plating treatment step of subjecting the aluminum alloy substrate for plating to degreasing, etching, and zincate treatment; and (j) a step of subjecting the surface of the aluminum alloy substrate subjected to the pre-plating treatment to electroless Ni-P plating treatment, and then polishing the surface subjected to the Ni-P plating treatment to obtain an aluminum alloy substrate for a magnetic disk; and (k) a step of forming a magnetic layer by adhering a magnetic material to the surface of the aluminum alloy substrate for a magnetic disk. It has the above steps. Hereinafter, each step (e) to (k) will be described in detail. The following will describe each step (e) to (k) in detail.

[0038] (e) Step of heating the aluminum alloy ingot and performing a homogenization treatment The aluminum alloy ingot obtained as described above is heated to perform a homogenization treatment. The homogenization treatment is preferably carried out at a heating temperature of 480 °C or higher and 560 °C or lower for 1 hour or more, more preferably at a heating temperature of 500 °C or higher and 550 °C or lower for 2 hours or more. When the heating temperature is less than 480 °C or the heating time is less than 1 hour, a sufficient homogenization effect may not be obtained. Also, when the heating temperature exceeds 560 °C, the aluminum alloy ingot may melt. In addition, although the upper limit of the heating time is not particularly limited, if it exceeds 48 hours, the homogenization effect may saturate and there is a risk of causing a decrease in productivity.

[0039] (f) Rolling process Next, in the rolling process, the homogenized aluminum alloy ingot is rolled into an aluminum alloy plate. In the rolling process, rolling can be performed once or multiple times, and cold rolling and hot rolling can be carried out as the rolling treatment. In one example, the homogenized aluminum alloy ingot is used to produce a hot-rolled plate by hot rolling. The conditions for hot rolling are not particularly limited but it is preferably that the hot rolling start temperature is 300 °C or higher and 500 °C or lower, more preferably 320 °C or higher and 480 °C or lower. Also, it is preferably that the hot rolling end temperature is 260 °C or higher and 400 °C or lower, more preferably 280 °C or higher and 380 °C or lower. If the hot rolling start temperature is less than 300 °C, the workability by hot rolling cannot be ensured, and if it exceeds 500 °C , the crystal grains become coarser, and there is a possibility that the adhesion of the Ni-P plating layer formed in the subsequent process decreases . Also, if the hot rolling end temperature is less than 260 °C, the workability by hot rolling cannot be ensured , and if it exceeds 400 °C, the crystal grains become coarser, and the Ni-P plating layer formed in the subsequent process has a problem. ​There may be a case where the adhesion decreases. In hot rolling, usually, an aluminum alloy ingot is heated and held at a hot rolling start temperature in the range of 0.5 hours or more and 10.0 hours or less, and then hot rolling is performed. After that, in one example, the obtained hot rolled sheet is cold rolled to produce a cold rolled sheet preferably having a thickness of 0.4 mm or more and 2.0 mm or less, more preferably 0.6 mm or more and 2.0 mm or less. That is, after hot rolling is completed, it is finished to the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, but may be determined according to the required plate strength and plate thickness of the aluminum alloy plate. The rolling ratio is preferably 20% or more and 90% or less, and more preferably 20% or more and 80% or less. If this rolling ratio is less than 20%, the crystal grains may coarsen during the pressure flattening annealing of the disk blank described later, and the adhesion of the Ni-P plating layer formed in the process described later may decrease. On the other hand, if this rolling ratio exceeds 90%, the manufacturing time may become long and there is a risk of causing a decrease in productivity.

[0040] Next, in one example, the obtained hot rolled sheet is cold rolled to produce a cold rolled sheet preferably having a thickness of 0.4 mm or more and 2.0 mm or less, more preferably 0.6 mm or more and 2.0 mm or less. That is, after hot rolling is completed, it is finished to the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, but may be determined according to the required plate strength and plate thickness of the aluminum alloy plate. The rolling ratio is preferably 20% or more and 90% or less, and more preferably 20% or more and 80% or less. If this rolling ratio is less than 20%, the crystal grains may coarsen during the pressure flattening annealing of the disk blank described later, and the adhesion of the Ni-P plating layer formed in the process described later may decrease. On the other hand, if this rolling ratio exceeds 90%, the manufacturing time may become long and there is a risk of causing a decrease in productivity. To ensure good cold rolling workability, annealing treatment may be optionally performed before or during cold rolling. When annealing treatment is performed, for example, in batch annealing, it is preferably performed under the conditions of an annealing temperature of 300°C or more and 450°C or less for 0.1 hour or more and 10 hours or less, and more preferably under the conditions of an annealing temperature of 300°C or more and 380°C or less for 1 hour or more and 5 hours or less. If the annealing temperature is less than 300°C and / or the annealing time is less than 0.1 hour, a sufficient annealing effect may not be obtained. Also, if the annealing temperature exceeds 450°C, the crystal grains may coarsen and the adhesion of the Ni-P plating layer formed in the process described later may decrease. There may be a case where the adhesion decreases. In hot rolling, usually, an aluminum alloy ingot is heated and held at a hot rolling start temperature in the range of 0.5 hours or more and 10.0 hours or less, and then hot rolling is performed. After that, in one example, the obtained hot rolled sheet is cold rolled to produce a cold rolled sheet preferably having a thickness of 0.4 mm or more and 2.0 mm or less, more preferably 0.6 mm or more and 2.0 mm or less. That is, after hot rolling is completed, it is finished to the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, but may be determined according to the required plate strength and plate thickness of the aluminum alloy plate.

[0041] To ensure good cold rolling workability, annealing treatment may be optionally performed before or during cold rolling. When annealing treatment is performed, for example, in batch annealing, it is preferably performed under the conditions of an annealing temperature of 300°C or more and 450°C or less for 0.1 hour or more and 10 hours or less, and more preferably under the conditions of an annealing temperature of 300°C or more and 380°C or less for 1 hour or more and 5 hours or less. If the annealing temperature is less than 300°C and / or the annealing time is less than 0.1 hour, a sufficient annealing effect may not be obtained. Also, if the annealing temperature exceeds 450°C, the crystal grains may coarsen and the adhesion of the Ni-P plating layer formed in the process described later may decrease. To ensure good cold rolling workability, annealing treatment may be optionally performed before or during cold rolling. When annealing treatment is performed, for example, in batch annealing, it is preferably performed under the conditions of an annealing temperature of 300°C or more and 450°C or less for 0.1 hour or more and 10 hours or less, and more preferably under the conditions of an annealing temperature of 300°C or more and 380°C or less for 1 hour or more and 5 hours or less. If the annealing temperature is less than 300°C and / or the annealing time is less than 0.1 hour, a sufficient annealing effect may not be obtained. Also, if the annealing temperature exceeds 450°C, the crystal grains may coarsen and the adhesion of the Ni-P plating layer formed in the process described later may decrease. There may be a case where the adhesion decreases. In hot rolling, usually, an aluminum alloy ingot is heated and held at a hot rolling start temperature in the range of 0.5 hours or more and 10.0 hours or less, and then hot rolling is performed. If the annealing time exceeds 10 hours, the manufacturing time may become longer, which may result in a decrease in productivity. There is.

[0042] On the other hand, in continuous annealing, the annealing temperature is between 400°C and 500°C and held for 60 seconds or less. It is preferable to carry out the annealing under the conditions of 450°C to 500°C for 30 seconds or less. It is more preferable to perform the annealing under the condition of a long time. If the annealing temperature is less than 400°C, the annealing effect is not sufficient. If the annealing temperature exceeds 500°C, the crystal grains become coarse and the The adhesion of the Ni-P plating layer formed during the process may decrease. If the time exceeds 20 seconds, the crystal grains will become coarse and the adhesion of the Ni-P plating layer formed in the process described below will be weakened. In addition, cooling may be started immediately after the desired annealing temperature is reached.

[0043] The aluminum alloy plate is produced by the above steps. A magnetic disk is manufactured by carrying out the following steps on the aluminum alloy plate.

[0044] (g) pressing and flattening the aluminum alloy plate into an annular disk blank; The aluminum alloy plate obtained by the rolling process as described above is punched into a ring shape. In one example, a circular disk blank is heated to 300°C in air. at a temperature of 300°C or higher and 450°C or lower for 30 minutes or more, and preferably at a temperature of 300°C or higher and 380°C or lower for 6 minutes or more. The blank is subjected to pressure annealing for 10 minutes or more to produce a flattened circular disk blank. If the treatment temperature is less than 300° C. and / or the treatment time is less than 30 minutes, the flattening effect is not sufficiently obtained. In addition, if the treatment temperature exceeds 450°C, the crystal grains become coarse, and as described below, The adhesion of the Ni-P plating layer formed in the step may decrease. The upper limit of the processing time is not particularly limited, but if it exceeds 24 hours, the manufacturing time will become long, which may lead to a decrease in productivity. In addition, the pressure in the pressure annealing is usually 0.1 MPa or more and 3.0 MPa or less.

[0045] (h) Step of subjecting the annular disk blank to cutting and grinding to obtain an aluminum alloy substrate for plating Next, the annular disk blank flattened in the cutting and grinding process is subjected to cutting and grinding. Then, optionally, stress relief heat treatment for relieving the stress of the annular disk blank is performed under the conditions of a temperature of 200°C or more and 290°C or less for 0.1 hour or more and 10 .0 hours or less.

[0046] (i) Pretreatment step for plating The aluminum alloy substrate for plating prepared as described above is subjected to degreasing, etching, and zincate treatment (Zn replacement treatment) as pretreatment for plating. Degreasing is performed, for example, using a commercially available AD -68F (manufactured by Uemura Kogyo Co., Ltd.) degreasing solution or the like, under the conditions of a degreasing temperature of 40°C or more and 70°C or less, a degreasing time of 3 minutes or more and 10 minutes or less, and a concentration of the degreasing solution of 200 mL / L or more and 800 mL / L or less. It is preferably performed under the conditions of a degreasing temperature of 45°C or more and 65°C or less, a degreasing time of 4 minutes or more and 8 minutes or less, and a concentration of the degreasing solution of 300 mL / L or more and 700 mL / L or less. If the degreasing temperature is less than 40°C, the degreasing time is less than 3 minutes, and / or the concentration of the degreasing solution is less than 200 mL / L, a sufficient degreasing effect may not be obtained. In addition, if the degreasing temperature exceeds 70°C, the degreasing time exceeds 10 minutes, and / or the concentration of the degreasing solution exceeds 800 mL / L, the smoothness of the surface of the aluminum alloy substrate for plating will decrease, and pits will occur after the plating process, resulting in flatness​ The slipperiness may decrease.

[0047] Etching is performed using, for example, a commercially available etching solution such as AD-107F (manufactured by Uemura Kogyo Co., Ltd.), at an etching temperature of 50°C or higher and 75°C or lower, an etching time of 0.5 minutes or longer and 5 minutes or shorter, and 20 mL / L or higher and 100 mL / L or lower of the concentration of the etching solution, preferably at an etching temperature of 5 5°C or higher and 70°C or lower, an etching time of 0.5 minutes or longer and 3 minutes or shorter, and 40 m L / L or higher and 100 mL / L or lower of the concentration of the etching solution is more preferable. If the etching temperature is less than 50°C, the etching time is less than 0.5 minutes, and / or the concentration of the etching solution is less than 20 mL / L, a sufficient etching effect may not be obtained. Also, if the etching temperature exceeds 75°C, the etching time exceeds 5 minutes, and / or the concentration of the etching solution exceeds 100 mL / L, the smoothness of the surface of the aluminum alloy substrate for plating may decrease, and pits may occur after the plating process, resulting in a decrease in smoothness. Note that a normal desmatt treatment may be performed between the etching treatment and the subsequent zincate treatment described below. .

[0048] The zincate treatment is performed using, for example, a commercially available zincate treatment solution such as AD-301F-3X (manufactured by Uemura Kogyo Co., Ltd.), at a zincate treatment temperature of 10°C or higher and 35°C or lower, a zincate treatment time of 0.1 minutes or longer and 5 minutes or shorter, and 100 mL / L or higher and 500 mL / L or lower of the concentration of the zincate treatment solution under the conditions, preferably at a zincate treatment temperature of 15°C or higher and 30°C or lower, a zincate treatment time of 0.1 minutes or longer and 2 minutes or shorter, and 200 mL / L or higher and 400 mL / L or lower of the concentration of the zincate treatment solution is more preferable. If the zincate treatment temperature is less than 10°C, zinc The degreasing treatment time is less than 0.1 minute, and / or the concentration of the zincate treatment solution is less than 100 mL / L In this case, the zincate film becomes non-uniform, pits may occur after the plating treatment, and the smoothness decreases There may be such a case. Also, when the zincate treatment temperature exceeds 35 °C, the zincate treatment time exceeds 5 minutes and / or the concentration of the zincate treatment solution exceeds 500 mL / L, the zincate film may become non-uniform, pits may occur after the plating treatment, and the smoothness may decrease There is a case.

[0049] (j) Step of obtaining an aluminum alloy substrate for magnetic disk Next, electroless Ni-P plating treatment is performed as a base treatment on the surface of the zincate-treated aluminum alloy substrate for plating, and then polishing of its surface is carried out. The electroless Ni-P plating treatment uses, for example, a commercially available electroless nickel plating solution such as Nimden HDX (manufactured by Uemura Kogyo Co., Ltd.), and is preferably carried out under the conditions of a plating treatment temperature of 80 °C or higher and 95 °C or lower, a plating treatment time of 100 minutes or longer and 180 minutes or shorter, and a Ni concentration in the plating solution of 3 g / L or higher and 10 g / L or lower. More preferably, it is carried out under the conditions of a plating treatment temperature of 85 °C or higher and 95 °C or lower, a plating treatment time of 100 minutes or longer and 120 minutes or shorter, and a Ni concentration in the plating solution of 4 g / L or higher and 9 g / L or lower. When the plating treatment temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the plating growth rate is slow, and there is a risk of reducing productivity. Also, when the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity 3 g / L or more and 10 g / L or less, and it is preferably carried out under the conditions of a plating treatment temperature of 85 °C or higher and 95 °C or lower, a plating treatment time of 100 minutes or longer and 120 minutes or shorter, and a Ni concentration in the plating solution of 4 g / L or higher and 9 g / L or lower. When the plating treatment temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the plating growth rate is slow, and there is a risk of reducing productivity. Also, when the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity ℃ or higher and 95 °C or lower, a plating treatment time of 100 minutes or longer and 120 minutes or shorter, and a Ni concentration in the plating solution of 4 g / L or higher and 9 g / L or lower. When the plating treatment temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the plating growth rate is slow, and there is a risk of reducing productivity. Also, when the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity / L or more and 9 g / L or less. When the plating treatment temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the plating growth rate is slow, and there is a risk of reducing productivity. Also, when the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity If the plating treatment temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the plating growth rate is slow, and there is a risk of reducing productivity and the smoothness of the plating surface may decrease. Also, when the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity If the plating treatment time is less than 100 minutes, a large number of defects may occur on the plating surface, and the smoothness of the plating surface may decrease. On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity On the other hand, when the plating treatment temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity and the smoothness of the plating may decrease. Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity Also, when the plating treatment time exceeds 180 minutes, the manufacturing time becomes long, and there is a risk of reducing productivity There is. Further, the surface of the underlying (Ni-P) plating layer is subjected to a polishing treatment. By these plating pretreatment and the underlying (Ni-P) plating treatment (with polishing), an aluminum alloy substrate for a magnetic disk is produced.

[0050] (k) Step of forming a magnetic layer After the electroless Ni-P plating treatment including the polishing treatment, a magnetic material is deposited on the Ni-P plating layer by sputtering to form a magnetic layer. The magnetic layer may be a single layer or may be formed of a plurality of layers having different compositions from each other. After sputtering, if necessary, a protective layer made of a carbon-based material may be formed on the magnetic layer by CVD, and a lubricating layer may be formed by applying a lubricating oil on the protective layer.

[0051] 4. Magnetic disk The magnetic disk of the present invention can be produced by the above-described method for manufacturing a magnetic disk. The magnetic disk of the present invention includes an aluminum alloy substrate for a magnetic disk, a Ni-P plating layer on the surface of the aluminum alloy substrate for the magnetic disk, and a magnetic layer formed on the Ni-P plating layer. Further, a protective layer or a lubricating layer may be formed on the magnetic layer. Such a magnetic disk of the present invention is beneficial as a magnetic disk excellent in reducing environmental load because it is produced using the above-described recycled material.

[0052] 5. Hard disk drive The hard disk drive of the present invention includes one or a plurality of the above-described magnetic disks, a spindle motor for rotating the magnetic disk, and a clamp portion for fixing the inner diameter side portion of the magnetic disk. ​​​​​​​​​​​​a material, a magnetic head that performs data processing on a magnetic disk, and an actuator that movably supports the magnetic head with respect to the magnetic disk and a swing arm that rotates and positions the actuator. Such a hard disk drive of the present invention is manufactured using the above-described recyclable material, and thus is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact. The hard disk drive of the present invention includes a material, a magnetic head that performs data processing on a magnetic disk, an actuator that movably supports the magnetic head with respect to the magnetic disk, and a swing arm that rotates and positions the actuator. Since such a hard disk drive of the present invention is manufactured using the above-described recyclable material, it is excellent in reducing environmental impact. In particular, a hard disk drive used in a data center or the like performs a large amount of data processing, and thus includes a large number of magnetic disks. By manufacturing many of the magnetic disks in such a hard disk drive using a recyclable material, it is possible to make it particularly excellent in reducing environmental impact.

[0053] Based on the above embodiments, the present invention relates to the following [1] to

[11] . [1] A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A film removing step of removing a film from a recyclable material having an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate to obtain an aluminum alloy material, a step of preparing a molten aluminum alloy using the aluminum alloy material as at least part of a raw material, a step of heating and holding the prepared molten metal, and a step of casting the heated and held molten metal to obtain an aluminum alloy ingot. A recycling method for an aluminum alloy substrate having the above steps. A recycling method for an aluminum alloy substrate having the above steps. [2] The recycling method for an aluminum alloy substrate according to the above [1], wherein the film contains Ni. [3] In the film removing step, the film is removed from the recyclable material by immersing the recyclable material in a solution. The recycling method for an aluminum alloy substrate according to the above [1] or [2]. In the film removing step, the film is removed from the recyclable material by immersing the recyclable material in a solution. The recycling method for an aluminum alloy substrate according to the above [1] or [2]. In the film removing step, the film is removed from the recyclable material by immersing the recyclable material in a solution. The recycling method for an aluminum alloy substrate according to the above [1] or [2]. [4] The solution is an acidic solution containing nitrate ions, and the aluminum alloy substrate according to the above [3]. Method for recycling aluminum alloy substrate sheets [5] The acidic solution has a temperature of 40 to 60 °C and a nitrate ion concentration of 25 mass% or more, , In the film removal step, the recycled material is immersed in the acidic solution for 1 hour or more, Method for recycling aluminum alloy substrate sheets according to the above [4]. [6] The total concentration of anions other than nitrate ions in the acidic solution is 5 mass% or less, and the method for recycling aluminum alloy substrate sheets according to the above [4] or [5]. [7] In the film removal step, a plurality of the recycled materials are immersed in the solution so that each of the recycled materials does not come into contact, Method for recycling aluminum alloy substrate sheets according to any one of the above [3] to [6]. Method for recycling aluminum alloy substrate sheets according to any one of the above [1] to [7]. [8] The aluminum alloy substrate constituting the recycled material is annular, and the method for recycling aluminum alloy substrate sheets according to any one of the above [1] to [7 . [9] A step of heating the aluminum alloy ingot obtained by the method for recycling aluminum alloy substrate sheets according to any one of the above [1] to [8] and performing a homogenization treatment, A rolling step of rolling the homogenized aluminum alloy ingot into an aluminum alloy sheet, A step of pressure flattening the aluminum alloy sheet obtained by the rolling step into an annular disk blank, and A step of subjecting the pressure-flattened annular disk blank to cutting and grinding to obtain an aluminum alloy substrate for plating, and A step of subjecting the aluminum alloy substrate for plating to degreasing, etching, and zincate treatment, to obtain an aluminum alloy substrate for plating, and a step of subjecting the aluminum alloy substrate for plating to degreasing, etching, and zincate treatment a pre-treatment step, performing electroless Ni-P plating treatment on the surface of an aluminum alloy substrate subjected to plating pre-treatment, then polishing the surface subjected to the Ni-P plating treatment to obtain an aluminum alloy substrate for a magnetic disk, a step of obtaining; forming a magnetic layer by attaching a magnetic material to the surface of the aluminum alloy substrate for the magnetic disk, a step of forming; A method for manufacturing a magnetic disk having the above.

[10] A magnetic disk obtained by the method for manufacturing a magnetic disk according to [9] above.

[11] A hard disk drive including the magnetic disk according to

[10] above.

[0054] The method for recycling an aluminum alloy substrate, the method for manufacturing a magnetic disk, the magnetic disk, and the hard disk drive according to the present embodiment have been described above. However, the present invention is not limited to the above embodiments, and various modifications and changes are possible based on the technical idea of the present invention. The present invention is not limited to the above embodiments, and various modifications and changes are possible based on the technical idea of the present invention.

Example

[0055] Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to these.

[0056] As a recycled material, an aluminum alloy substrate made of JIS 5086 alloy (Al-Mg alloy), and a Ni-P plating layer (film) with a thickness of 10 μm formed on the aluminum alloy substrate by electroless Ni-P plating treatment, and an aluminum alloy substrate for a magnetic disk (hereinafter referred to as "sample"; outer diameter 95 mm, inner diameter 25 mm, overall thickness 1.3 m substrate (hereinafter referred to as "sample"; outer diameter 95 mm, inner diameter 25 mm, overall thickness 1.3 m m) was used. The samples of each example were immersed in an acidic solution under the conditions shown in Table 1. In addition, each example's acidic solution consisted of an acid component of nitric acid, hydrochloric acid, and sulfuric acid, and water, and the total content of the acid component and water was 100% by mass.

[0057] The composition of the aluminum alloy used for the aluminum alloy substrate was 0.02% by mass of Fe, 0 .018% by mass of Si, 4.02% by mass of Mg, 0.35% by mass of Zn, 0.052% by mass of Cr, with the balance being Al, inevitable impurities, and trace components.

[0058]

Table 1

[0059] The measurement of the "weight loss of the sample" and the "evaluation of film removal" described in Table 1 above were carried out as follows . (Measurement of the weight loss of the sample) The mass of the sample before immersion in the acidic solution was measured in advance. Next, after the sample after immersion in the acidic solution was washed with pure water and dried with a warm air dryer, the mass was measured again. After that, {(mass of the sample before immersion in the acidic solution) - (mass of the sample after immersion in the acidic solution)} / (specific gravity of the Ni-P plating layer × total surface area of the sample) was calculated, and the weight loss of the sample was measured as the weight loss per side of the sample. The specific gravity of the Ni-P plating layer was 7 .6 g / m was used. . 3 was used.

[0060] (Evaluation of film removal) Visually, the overall appearance including the outer peripheral part of the sample after immersion in the acidic solution was observed, and when the Ni-P plating layer was not confirmed and the Ni-P plating layer was completely removed, it was rated as "◎" ​​When evaluated as "○", and when the remaining Ni-P plating layer was confirmed, it was evaluated as "×".

[0061] (Evaluation of recyclability) A 1 kg sample consisting of a plurality of samples with the Ni-P plating layer removed under the conditions of Example 1 was obtained. Arbitrarily select 6 samples from among the plurality of samples with the Ni-P plating layer removed, and for each sample, analyze the composition of the aluminum alloy by the first spark discharge optical emission spectrometry, and calculate the average value of each detected element. Then, dissolve all 1 kg of the sample to prepare a molten metal and heat and hold it. After that, pour the molten metal into a mold and cast it to obtain an aluminum alloy ingot. Cut out the aluminum alloy ingot obtained after casting into an arbitrary size, and analyze the aluminum alloy composition by the same method as the first spark discharge optical emission spectrometry (second spark discharge optical emission spectrometry). Also, { (content of each element obtained by the second spark discharge optical emission spectrometry ) - (content of each element obtained by the first spark discharge optical emission spectrometry)} / (content of each element obtained by the first spark discharge optical emission spectrometry ) × 100 (%) (described as "change amount" in Table 2) was calculated. The results of the spark discharge optical emission spectrometry are shown in Table 2. The film of the sample used in each example was a Ni-P plating layer with a thickness of 10 μm. As shown in Table 1, in Examples 1 to 4, since the amount of material removed from the sample was 10 μm or more, it was confirmed that the Ni-P plating layer could be effectively removed. Also, as indicated by "◎" in Table 1, visually

[0062]

Table 2

[0063] The film of the sample used in each example was a Ni-P plating layer with a thickness of 10 μm. As shown in Table 1, in Examples 1 to 4, since the amount of material removed from the sample was 10 μm or more, it was confirmed that the Ni-P plating layer could be effectively removed. Also, as indicated by "◎" in Table 1, visually ​Even in the observation, it was confirmed that the Ni-P plating layer was completely removed in the samples of Examples 1 to 4. On the other hand, as shown in Table 1, in Comparative Examples 1 and 2, the amount of material removed from the samples was 0 μm, and the Ni-P plating layer could not be removed. Also, as indicated by "×" in Table 1, even in the visual observation, it was confirmed that the Ni-P plating layer remained in the samples of Comparative Examples 1 and 2.

[0064] As shown in Table 2, the change amounts of each element of Fe, Si, Mg, Zn, and Cr were 4.19 mass% or less. This change amount was acceptable, and it was confirmed that the composition hardly changed between the aluminum alloy before preparing the molten metal after removing the Ni-P plating layer and the aluminum alloy after preparing, heating and holding, and casting the molten metal.

Industrial Applicability

[0065] According to the present invention, a recycling method for an aluminum alloy substrate with excellent recyclability can be provided. ​

Claims

1. It has an aluminum alloy substrate and at least one layer of film on the aluminum alloy substrate. A film removal step of removing the film from the recycling material to obtain an aluminum alloy material, A step of preparing a molten aluminum alloy using at least part of the aluminum alloy material as a raw material, A step of preparing a molten aluminum alloy using at least part of the aluminum alloy material as a raw material, A step of heating and holding the prepared molten metal, A step of casting the heated and held molten metal to obtain an aluminum alloy ingot, A recycling method for an aluminum alloy substrate having the above steps.

2. The recycling method for an aluminum alloy substrate according to claim 1, wherein the film contains Ni.

3. In the film removal step, the film is removed from the recycling material by immersing the recycling material in a solution. The recycling method for an aluminum alloy substrate according to claim 1 or 2.

4. The recycling method for an aluminum alloy substrate according to claim 3, wherein the solution is an acidic solution containing nitrate ions.

5. The acidic solution has a temperature of 40 to 60°C and a nitrate ion concentration of 25% by mass or more. And In the film removal step, the recycling material is immersed in the acidic solution for 1 hour or more. The recycling method for an aluminum alloy substrate according to claim 4.

6. The total concentration of anions other than nitrate ions in the acidic solution is 5% by mass or less. The recycling method for an aluminum alloy substrate according to claim 4.

7. In the film removal step, so that each of the recycling materials does not come into contact with each other, a plurality of the The recycling method of the aluminum alloy substrate according to claim 3, wherein the recycling material is immersed in a solution. Method.

8. The aluminum alloy substrate constituting the recycling material is annular, and the recycling method of the aluminum alloy substrate according to claim 1 or 2.

9.

9. A step of heating the aluminum alloy ingot obtained by the recycling method of the aluminum alloy substrate according to claim 1 or 2 and performing a homogenization treatment; A rolling step of rolling the homogenized aluminum alloy ingot into an aluminum alloy plate; And A step of pressure flattening the aluminum alloy plate obtained by the rolling step into an annular disk blank; A step of performing cutting and grinding on the pressure-flattened annular disk blank to obtain an aluminum alloy substrate for plating; And A pre-plating treatment step of subjecting the aluminum alloy substrate for plating to degreasing, etching, and zincate treatment; A step of subjecting the surface of the aluminum alloy substrate subjected to the pre-plating treatment to electroless Ni-P plating treatment, and then polishing the surface subjected to the Ni-P plating treatment to obtain an aluminum alloy substrate for a magnetic disk; A step of forming a magnetic layer by attaching a magnetic material to the surface of the aluminum alloy substrate for the magnetic disk; And a manufacturing method of a magnetic disk having After performing electroless Ni-P plating treatment on the surface of the aluminum alloy substrate subjected to the pre-plating treatment, polishing the surface subjected to the Ni-P plating treatment to obtain an aluminum alloy substrate for a magnetic disk; A step of forming a magnetic layer by attaching a magnetic material to the surface of the aluminum alloy substrate for the magnetic disk; And a manufacturing method of a magnetic disk having A step of forming a magnetic layer by attaching a magnetic material to the surface of the aluminum alloy substrate for the magnetic disk; And a manufacturing method of a magnetic disk having A manufacturing method of a magnetic disk.

10. A magnetic disk obtained by the manufacturing method of the magnetic disk according to claim 9.

11. A hard disk drive including the magnetic disk according to claim 10.

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