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 applying electricity to a recycled material, which has an aluminum alloy substrate and at least one Ni-containing film layer on the aluminum alloy substrate, with the recycled material being immersed in a solution, thereby removing the film from the recycled material to provide an aluminum alloy material.SELECTED DRAWING: Figure 1

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, including 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 for 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 in 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 by the following manufacturing process. First, an aluminum alloy having a desired chemical composition is cast, the ingot is homogenized, then hot-rolled, and then cold-rolled to produce an aluminum alloy plate having a 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, grinding, degreasing, etching, and zincate treatment (Zn substitution treatment) as pre-treatment, and then Ni-P electroless plating treatment, which is a hard non-magnetic metal, is performed as a base treatment, and the surface subjected to the Ni-P electroless plating treatment is polished to manufacture an aluminum alloy substrate for magnetic disks. and punching 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, grinding, degreasing, etching, and zincate treatment (Zn substitution treatment) as pre-treatment, and then Ni-P electroless plating treatment, which is a hard non-magnetic metal, is performed as a base treatment, and the surface subjected to the Ni-P electroless plating treatment is polished to manufacture an aluminum alloy substrate for magnetic disks. 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 progressing. From such current situations, the increase in the capacity of HDDs has become essential. For increasing the capacity of HDDs, it is important to increase the number of magnetic disks mounted and to increase 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 magnetic disks. Although both of the above methods are technically possible, when both of the above methods are performed, the yield in the manufacturing process of magnetic disks deteriorates. Specifically, when the magnetic disk is made thinner in the former case, higher processing accuracy is required in rolling, grinding, etc., and for the defects on the Ni-P surface in the latter case, the threshold value for the number of occurrences becomes stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products increases, and considering the future demand for magnetic disks, 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 blanks are stacked, and annealing is performed while applying pressure from both sides to flatten them by pressure annealing.

[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 progressing. From such current situations, the increase in the capacity of HDDs has become essential. For increasing the capacity of HDDs, it is important to increase the number of magnetic disks mounted and to increase 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 magnetic disks. Although both of the above methods are technically possible, when both of the above methods are performed, the yield in the manufacturing process of magnetic disks deteriorates. Specifically, when the magnetic disk is made thinner in the former case, higher processing accuracy is required in rolling, grinding, etc., and for the defects on the Ni-P surface in the latter case, the threshold value for the number of occurrences becomes stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products increases, and considering the future demand for magnetic disks, the annular disk blanks are stacked, and annealing is performed while applying pressure from both sides to flatten them by pressure annealing. Specifically, when the magnetic disk is made thinner in the former case, higher processing accuracy is required in rolling, grinding, etc., and for the defects on the Ni-P surface in the latter case, the threshold value for the number of occurrences becomes stricter. That is, the number of aluminum alloy substrates for magnetic disks that become defective products increases, and considering the future demand for magnetic disks, 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 blanks are stacked, and annealing is performed while applying pressure from both sides to flatten them by pressure annealing. 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 have become apparent regarding the types of metals. Although aluminum is a metal type that is relatively easy to recycle, the difficulty of recycling varies depending on its alloy system. For example, in the case of aluminum can materials, the same alloy can be collected as raw materials and can be easily made into aluminum can materials again. However, the aluminum clad material used as a heat exchanger material 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, and since it changes from the original alloy compositions during remelting and casting, the range of uses 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 the purpose of improving plating defects and limit the contents 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 somewhat to environmental protection.

[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 materials 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 ingot as a casting is not good in terms of recycling efficiency. For this reason, it has been desired to recycle the defective aluminum alloy substrate for magnetic disks as a rolled material, preferably as an aluminum alloy material for magnetic disks again.

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

[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. In this technology, although the recycling of the aluminum alloy substrate is possible, it is difficult to efficiently use an aluminum alloy substrate using high-purity ingot.

[0010] Patent Document 2 discloses a method of recycling an aluminum alloy substrate after removing the Ni-P plating layer by returning it to the plating process again. In this technology, the recycled aluminum alloy substrate can be recycled. However, recently, the requirements for defects in the Ni-P plating layer of aluminum alloy substrates for magnetic disks have become extremely strict. Therefore, the aluminum alloy substrate with the film such as the Ni-P plating layer peeled off by the method of Patent Document 2 is directly recycled When used, the aluminum alloy substrate with damaged surface is plated. Therefore, there was a possibility that defects on the plated surface occurred frequently.

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

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 have found that the film can be effectively removed by energizing the recycling material in a state where the recycling material having an aluminum alloy substrate and a film containing at least one layer of Ni is immersed in a solution, and have completed the present invention.

[0015] The recycling method for an aluminum alloy substrate according to an embodiment of the present invention is an aluminum alloy substrate and at least one layer of Ni-containing While the recycling material having a film is immersed in a solution, an electric current is passed through the recycling material to remove the film from the recycling material to obtain an aluminum alloy material. A film removal step is included. By passing an electric current through the recycling material while the recycling material having a film is immersed in a solution, the film is removed from the recycling material to obtain an aluminum alloy material. There is a film removal step.

Advantages of the Invention

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

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail.

[0019] 1. Method for Recycling Aluminum Alloy Substrate The method for recycling an aluminum alloy substrate in the present invention is (a) A film removal step of obtaining an aluminum alloy material by removing a film from a recycling material by passing an electric current through the recycling material while the recycling material having an aluminum alloy substrate and at least one layer of a film containing Ni on the aluminum alloy substrate is immersed in a solution. has. In the film removal step of the method for recycling an aluminum alloy substrate of the present invention, while the recycling material having an aluminum alloy substrate and at least one layer of a film containing Ni on the aluminum alloy substrate is immersed in a solution, an electric current is passed through the recycling material. has. In the method for recycling an aluminum alloy substrate of the present invention, in the film removal step, an aluminum alloy substrate and a recycling material having at least one layer of a film containing Ni on the aluminum alloy substrate are immersed in a solution, and an electric current is passed through the recycling material. By doing so, A film is removed from the recycled material to obtain an aluminum alloy material. In the prior art, an aluminum alloy substrate with a film containing Ni removed was recycled as it was, and a film such as a Ni-P plating layer was formed on the aluminum alloy substrate. For this reason, there were cases where defects occurred on the film. On the other hand, in the method for recycling an aluminum alloy substrate of the present invention, the film containing Ni can be effectively removed from the recycled material in the film removal step. As a result, the present invention can provide a method for recycling an aluminum alloy substrate with excellent recyclability. In addition, since the amount of use of expensive high-purity aluminum ingots can be reduced without degrading performance, cost reduction can be achieved. Also, in one aspect, the aluminum alloy material obtained after removing the film containing Ni is used as it is as a raw material to prepare a molten aluminum alloy and perform subsequent steps, thereby manufacturing an aluminum alloy plate maintaining the alloy composition of the aluminum alloy material. In this aspect, when preparing the molten aluminum alloy, by adding an arbitrary material, element, aluminum alloy ingot, etc. to the molten metal, an aluminum alloy plate with a desired alloy composition can also be manufactured. Also, by setting the conditions when heating and holding the molten metal, manufacturing 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 plate can be set to desired properties and characteristics different from those of the recycled material. Since the rolled aluminum alloy plate can have few surface defects, when forming a film on the aluminum alloy plate, the defects of the film can also be reduced. The aluminum alloy substrate with the film removed was recycled as it was. A film such as a Ni-P plating layer was formed on the aluminum alloy substrate. For this reason, there were cases where defects occurred on the film. In the film removal step of the aluminum alloy substrate recycling method of the present invention, the film containing Ni can be effectively removed from the recycled material. As a result, the present invention can provide a method for recycling an aluminum alloy substrate with excellent recyclability. Also, since the amount of use of expensive high-purity aluminum ingots can be reduced without degrading performance, cost reduction can be achieved. Also, in one aspect, After removing the film containing Ni, the obtained aluminum alloy material is used as it is as a raw material to prepare a molten aluminum alloy and perform subsequent steps, thereby manufacturing an aluminum alloy plate maintaining the alloy composition of the aluminum alloy material. In this aspect, when preparing the molten aluminum alloy, by adding an arbitrary material, element, aluminum alloy ingot, etc. to the molten metal, an aluminum alloy plate with a desired alloy composition can also be manufactured. Also, by setting the conditions when heating and holding the molten metal, manufacturing 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 plate can be set to desired properties and characteristics different from those of the recycled material. Since the rolled aluminum alloy plate can have few surface defects, when forming a film on the aluminum alloy plate, the defects of the film can also be reduced. to few.

[0020] (Recycled materials) The "recycled material" used in the present invention refers to an aluminum alloy substrate and the aluminum The material has a coating on a aluminum alloy substrate. Examples of recycled materials include magnetic discs. Examples of "intermediate materials" include intermediate materials and finished products that are generated during the disk manufacturing process. For example, an aluminum alloy substrate for a magnetic disk corresponds to the above, and an example of a "finished product" is, These recycled materials are defective products, non-standard products, and magnetic disks. In the case of disks, this applies to used ones. Also, the "film" is made of an aluminum alloy A substrate has one or more layers formed thereon, and the one or more layers The coating has a layer containing Ni. The coating may be composed of a layer containing Ni and a layer not containing Ni. An example of a layer containing Ni is a Ni-P plating layer. Examples of the layers that can be used include a magnetic layer, a protective layer, and a lubricating layer. The shape is not particularly limited, and may be a circular ring, a polygonal shape, or an indefinite shape having no specific shape. Many recycled materials are circular, and it is easy to procure circular recycled materials. Therefore, it is preferable that the aluminum alloy substrate constituting the recycled material has a circular ring shape. In the known recycling method for aluminum alloy substrates, the aluminum obtained by the coating removal process is The aluminum alloy material is used as at least a part of the raw material, The aluminum alloy material may be used as the raw material alone, or other materials or elements may be used together with the aluminum alloy material as the raw material. It may also be used as. The intermediate materials and finished products are described in more detail below.

[0021] (Intermediate material) Examples of the intermediate material include aluminum alloy substrates for magnetic disks generated during the manufacturing process of magnetic disks. In one example, a film containing Ni such as a Ni-P plating layer is formed on the surface of the aluminum alloy substrate for magnetic disks. The content of Ni in the film containing Ni used for the aluminum alloy substrate for magnetic disks is, for example, 80% by mass or more and 95% by mass or less. When the film containing Ni is a Ni-P plating layer, the content of P 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 magnetic disks is, for example, 0.3 mm or more and 2.0 mm or less.

[0022] (Finished product) Examples of the finished product include magnetic disks. In one example of a magnetic disk, as a film on the surface of the aluminum alloy substrate for magnetic disks, a Ni-P plating layer, a CoCrPt-based magnetic layer, and a protective layer such as a carbon-based material 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 magnetic disk, which is the finished product, can also be used as at least part of the raw material to prepare a molten aluminum alloy.

[0023] 2. Steps 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 step (a).​​​ Hereinafter, step (a) will be described in detail.

[0024] (a) Film removal step In the film removal step, while the recycled material is immersed in the solution, an electric current is passed through the recycled material to remove the film from the recycled material and obtain an aluminum alloy material. Here, "passing an electric current" means passing an electric current through the recycled material immersed in the solution. By immersing the recycled material in the solution and passing an electric current through the recycled material, Ni in the film constituting the recycled material becomes Ni ions due to chemical and electrical actions and dissolves in the solution. As a result, the film containing Ni can be effectively removed. The method of passing an electric current through the recycled material is not particularly limited, but an example is a mode in which at least the positive electrode of the power source is electrically directly connected to the recycled material. The solution is preferably an acidic solution containing sulfate ions, and it is more preferable to remove the film by performing anodic electrolysis in a state where an electric connection is made between the recycled material immersed in the acidic solution and the counter electrode. An example of the recycled material 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, the inner diameter, and the outer diameter of the aluminum alloy substrate. By passing an electric current through the recycled material while immersed in the acidic solution, the Ni-P plating layer formed as a film on all such surfaces can be removed. In particular, when anodic electrolysis is performed in a state where an electric connection is made between the recycled material immersed in the acidic solution containing sulfate ions and the counter electrode, the Ni-P plating layer can be effectively removed. Further, an alumite film is formed on the surface of the aluminum alloy substrate exposed by the removal of the Ni-P plating layer. Since melting of the aluminum alloy substrate is thereby prevented, the Ni-P plating layer can be selectively removed. Also, when the recycled material is simply immersed in an alkaline solution without applying electric current, dissolution of Ni into the solution does not occur due to the corrosion resistance of the Ni-containing film such as the Ni-P plating layer in the alkaline solution, and it becomes difficult to remove the film. In contrast, by performing anodic electrolysis while connecting between the recycled material immersed in the acidic solution containing sulfate ions as described above and the counter electrode, it is possible to prevent dissolution of the aluminum alloy substrate while effectively and selectively removing the film containing Ni.

[0025] The acidic solution containing sulfate ions can be prepared by dissolving sulfuric acid or sulfates such as sodium sulfate in a solvent such as pure water, industrial water, or tap water. However, when using sulfates, it is necessary to further add sulfuric acid or nitric acid to make an acidic solution. Also, commercially available sulfuric acid aqueous solutions can be used. The sulfate ion concentration in the acidic solution is preferably 5 mass% or more, more preferably 7 mass% or more, and even more preferably 10 mass% or more. By the sulfate ion concentration in the acidic solution being within the above range, the film can be efficiently removed in a short time. Also, the pH of the acidic solution is preferably 0 to 4, more preferably 0 to 3, and even more preferably 1 to 2. By the pH of the acidic solution being within the above range, the film can be efficiently removed. When the acidic solution contains sulfate ions, anions such as chloride ions, nitrate ions, and phosphate ions may be present as anions other than sulfate ions in the acidic solution. The aluminum constituting the recycled material From the viewpoint of effectively preventing the dissolution of aluminum from the aluminum alloy substrate, in the acidic solution the concentration of anions other than sulfate ions is preferably 5% by mass or less.

[0026] While electrically connecting between the recycled material immersed in the acidic solution and the counter electrode, an anode As conditions for performing electrolysis, the temperature of the acidic solution, the time of anodic electrolysis, the material and size of the counter electrode, etc., the material and size of the recycled material, etc. can be appropriately set. The acidic solution preferably has a temperature of 20°C or higher, more preferably has a temperature of 20 to 50°C, and even more preferably has a temperature of 25 to 40°C. When the temperature of the acidic solution is within the above range, a film containing Ni can be efficiently removed in a short time, and equipment and energy for heating the acidic solution can be saved.

[0027] While electrically connecting between the recycled material immersed in the acidic solution and the counter electrode, an anode The counter electrode used when performing electrolysis is electrically directly connected to the negative electrode of the power source and is arranged to face the recycled material in the acidic solution. Also, a voltage is applied between the recycled material and the counter electrode by the power source. The material of the counter electrode is not particularly limited as long as anodic electrolysis of the recycled material can be performed. For example, Pt (platinum), Ni (nickel), Al (aluminum), C (carbon), etc. can be used. The shape of the counter electrode is not particularly limited. For example, it can be in a plate shape or a wire shape. The voltage applied between the recycled material and the counter electrode during anodic electrolysis is not particularly limited, but is preferably 2V or higher, more preferably 2.5V or higher, and even more preferably 3V or higher. When the voltage during anodic electrolysis is By being within the above range, a film containing Ni can be efficiently removed in a short time. Note that the recycled material and the counter electrode may each be entirely immersed in the acidic solution. Also, a part of each may be exposed above the acidic solution and the remaining part may be immersed in the acidic solution.

[0028] FIG. 1 is a diagram showing a process of performing anodic electrolysis in a film removal step according to an embodiment. As shown in FIG. 1(a), an anodic electrolysis apparatus 1 includes a container that houses an acidic solution 6 containing sulfuric acid (H2SO4), a recycled material having an aluminum alloy substrate 3 and a Ni-P plating layer (film) 2 formed on the aluminum alloy substrate 3, a counter electrode 4, and a power source 5. In the acidic solution 6, sulfuric acid (H2SO4) dissociates into sulfate ions (SO4 2- 2- 2- ). In the acidic solution 6, the recycled material and the counter electrode 4 are arranged to face each other, the positive electrode of the power source 5 is electrically directly connected to the recycled material through a conducting wire, and the negative electrode of the power source 5 is electrically directly connected to the counter electrode 4 through a conducting wire. In one example, the recycled material is an aluminum alloy substrate for an annular magnetic disk. When a voltage is applied between the recycled material and the counter electrode 4 from the power source 5, anodic electrolysis of the recycled material occurs and Ni starts to dissolve from the Ni-P plating layer 2 into the acidic solution 6. 2+ dissolves into the acidic solution 6.

[0029] As shown in FIG. 1(b), when the anodic electrolysis proceeds to a certain extent, a part of the Ni in the acidic solution 6 forms a salt (nickel sulfate; NiSO4 2+ 2- ) with the sulfate ions (SO4 ) in the acidic solution 6, and the remaining Ni 2+ is deposited as Ni on the counter electrode 4. As shown in FIG. 1(c),, when the anodic electrolysis further proceeds and the dissolution of Ni into the acidic solution 6 is completed, the Ni-P plating layer (film) 2 is removed from the surface of the recycled material immersed in the acidic solution 6, and the aluminum alloy substrate 3 is exposed. Since an alumite film 7 is formed on the surface of the aluminum alloy substrate 3, the anodic electrolysis will not proceed further. As will be described later with reference to FIG. 2 in the examples, at the stage of FIG. 1(a), a constant current flows between the recycled material and the counter electrode 4, showing a constant current density. However, at the stage of FIG. 1(b), as the surface area of the exposed aluminum alloy substrate 3 increases, the current flowing between the recycled material and the counter electrode 4 rapidly decreases, and accordingly, the current density also significantly decreases. Then, at the stage of FIG. 1(c), a constant current about 1 / 10 of the constant current at the stage of FIG. 1(a) flows between the recycled material and the counter electrode 4, and the current density also becomes a constant value significantly smaller than the current density at the stage of FIG. 1(a). By measuring the change in the current or current density of the anodic electrolysis in this way, when the current or current density significantly decreases from the initial constant current or constant current density of the anodic electrolysis and begins to become a constant constant current or constant current density, the Ni-P plating layer ( film) 2 is removed and the alumite film 7 is formed on the surface of the aluminum alloy substrate 3, which can be determined as the substantial end time of the anodic electrolysis. In the method for recycling an aluminum alloy substrate of the present invention, further, in the film removal step, Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is.

[0030] In the method for recycling an aluminum alloy substrate of the present invention, further, in the film removal step, Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is. This can have a step. In this way, the Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after the anodic electrolysis are recovered, and Ni is isolated or the acidic solution is used as it is. By doing so, it can be effectively utilized as a resource and the recyclability can be further improved. This can be achieved. The Ni recovered in this way can be used for various purposes as metallic Ni, or it can be used to adjust the alloy composition of the molten metal to a desired one in the process of preparing the molten aluminum alloy described later. It can also be used to adjust the composition of the plating solution for forming the Ni-P plating layer (film). Products can be made using the Ni recovered in this way and the acidic solution containing Ni (for example, a sulfuric acid solution containing Ni).

[0031] 3. Method for manufacturing a magnetic disk The method for manufacturing a magnetic disk of the present invention includes: (b) A step of preparing a molten aluminum alloy using at least a part of the aluminum alloy material obtained by the recycling method of the aluminum alloy substrate as a 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) A step of heating the aluminum alloy ingot to perform a homogenization treatment; (f) A rolling step of rolling the homogenized aluminum alloy ingot into an aluminum alloy plate; (g) A step of pressurizing and flattening the aluminum alloy plate obtained by the rolling step into an annular disk blank; (h) A step of subjecting the pressurized and flattened annular disk blank to cutting and grinding to obtain a plating aluminum alloy substrate; (i) A pre-plating treatment step of subjecting the plating aluminum alloy substrate to degreasing, etching, and zincate treatment; (j) A step of subjecting the surface of the aluminum alloy substrate subjected to the pre-plating treatment to electroless Ni-P plating treatment. After performing treatment, the surface subjected to Ni-P plating treatment is polished to obtain an aluminum alloy substrate for a magnetic disk, and (k) A step of forming a magnetic layer by attaching a magnetic material to the surface of the aluminum alloy substrate for a magnetic disk is included. has. Hereinafter, each step (b) to (k) will be described in detail.

[0032] (b) Step of preparing a molten aluminum alloy Using at least a part of the aluminum alloy material obtained in the film removal step as a raw material, a molten aluminum alloy is prepared. The content of each element in the molten metal prepared in step (b) is described below. is described.

[0033] · Ni (nickel) content The Ni content in the molten aluminum alloy is preferably 0 mass% or more and 2.5 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 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 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. is preferably 2.5 mass% or less, more preferably 0.5 mass% or less, and even more preferably 0.1 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. 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. is adjusted to the desired Ni content by adding aluminum alloy ingots or the like.

[0034] · P (phosphorus) content The P content in the molten aluminum alloy is preferably 0 mass% or more and 0.05 mass% or less. P is contained in aluminum alloy ingots etc., but the aluminum Combines with Mg (magnesium) commonly contained in the minium alloy to form Mg-P-based oxides, resulting in non-uniform reactions only in that part during plating treatment and generating large defects on the plating surface. This may occur. As a result, the smoothness of the plating surface decreases. Although a part of the Mg-P-based oxide can be removed by floating on the surface of the molten metal by heating and holding the molten metal, 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% by mass or less, and more preferably 0.01% by 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 adjust by adding aluminum alloy ingots or the like to achieve the desired content. However, when adjustment is necessary, aluminum ingots or the like are added in the same way as Ni to adjust to the desired content.

[0035] ·Mg (magnesium) content The Mg content in the molten metal of the aluminum alloy is preferably 0% by mass or more and 6.5% by 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 like P. The Mg content in the molten metal is preferably 6.5% by mass or less, and more preferably 4.5% by mass or less. When the Mg content is high, aluminum alloy ingots or the like are added in the same way as Ni to adjust to the desired content.

[0036] ·Metal components in the molten metal of the aluminum alloy Regarding the metal components contained in the molten metal of the aluminum alloy, as described above, the contents of Ni, P itself, and elements such as Cu and Mg that form intermetallic compounds with P are adjusted. ​ It is preferable to do so.

[0037] On the other hand, elements other than Ni, P, Cu and Mg and their contents are not particularly limited. The alloy composition contained in the molten aluminum alloy is, for example, as follows: Aluminum alloys contain Fe (iron) and, optionally, Mn (manganese). The total content of Fe and Mn is in the range of 0.005 mass% or more and 7.00 mass% or less. and further containing 0.5% by mass or more and 6.5% by mass or less of Mg, and optionally 0% by mass or less of Mg. More than 1.0% by mass of Si (silicon), more than 0% by mass of Zn (zinc) and less than 0.7% by mass , Cr (chromium) of 0 mass% to 0.30 mass%, and 0 mass% to 0.20 mass% The remaining Zr (zirconia) is The remaining part consists of Al and unavoidable impurities and other trace elements.

[0038] Inevitable impurities include Ti (titanium) and Ga (gallium) contained in aluminum alloys. ), and other trace elements include Co (cobalt) and Pt (platinum). The content of these unavoidable impurities and other trace elements is 0.1% for each element. As long as the content is 0 mass % or less, and the total content is 0.30 mass % or less, the effect of the present invention is not impaired.

[0039] (c) The process of heating and holding the molten metal Next, the molten aluminum alloy is heated and held. The molten metal is heated and held in a holding furnace. During this process, the oxide film that floats on the surface of the molten metal is removed outside the furnace. It is preferable to remove the oxide film before casting the aluminum alloy. By removing in the method such as etc., the content of Ni and P in the molten metal can be reduced. It can be done It is preferable to promptly remove the oxide film outside the furnace only.

[0040] (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 The molten metal is, if necessary, after the in-line degassing treatment and in-line filtration treatment described later, semi-continuous It is cast into an aluminum alloy ingot by a casting method (DC casting method), die casting method, continuous casting method (CC method), etc. In the DC casting method, the molten metal poured through the spout is directly discharged onto the bottom block And the wall of the water-cooled mold, and the outer peripheral part of the ingot (ingot), and heat is taken away by the cooling water And it solidifies and is pulled downward as an ingot. In the die casting method The molten metal poured into the hollow mold made of cast iron or the like is deprived of heat by the mold wall and solidifies, and the cast An ingot is produced. In the CC casting method, a 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 roll. .

[0041] 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 apparatus, degassing apparatuses commercially available under trademarks such as SNIF and ALPUR can be used. These in-line degassing treatment apparatuses rotate a rotating body with blades at high speed while blowing argon gas or a mixed gas of argon and nitrogen etc. Into the molten metal, and supply the gas as fine bubbles into the molten metal. Thereby, dehydrogen gas and inclusions are removed in-line in a short time And supply it into the molten metal. As a result, dehydrogen gas and inclusions are removed in-line in a short time It can be carried out in between. As the in-line filtration treatment, 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.

[0042] (e) Step of heating an aluminum alloy ingot to perform homogenization treatment Next, the aluminum alloy ingot obtained as described above is heated to perform homogenization treatment. Homogeneous In the homogenization treatment, preferably 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, the aluminum alloy ingot is heated. 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, at a heating temperature exceeding 560 °C, there is a risk that the aluminum alloy ingot will melt. Also, the upper limit of the heating time is not particularly limited but if it exceeds 48 hours, the homogenization effect may saturate and cause a decrease in productivity.

[0043] (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 is performed once or multiple times, and cold rolling or hot rolling can be performed 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. Heat If the intermediate rolling start temperature is less than 300°C, workability by hot rolling cannot be ensured. If it exceeds 500°C , the crystal grains become coarse, and there are cases where the adhesion of the Ni-P plating layer formed in the subsequent process deteriorates. Also, if the hot rolling finish temperature is less than 260°C, workability by hot rolling cannot be ensured. If it exceeds 400°C , the crystal grains become coarse, and there are cases where the adhesion of the Ni-P plating layer formed in the subsequent process deteriorates. In hot rolling, usually, the ingot is heated and held at the hot rolling start temperature for 0 .5 hours or more and 10.0 hours or less, and then hot rolling is performed.

[0044] 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 m m 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 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 become coarse in the pressure flattening annealing of the disk blank described later, and the adhesion of the Ni-P plating layer formed in the subsequent process may deteriorate. On the other hand, if this rolling ratio exceeds 90%, the manufacturing time becomes 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.

[0045] When performing annealing treatment, for example, in batch annealing , it is 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. ​It is preferably carried out under the conditions of an annealing temperature of 300°C or higher and 380°C or lower for 1 hour or longer and 5 hours or shorter. It is more preferably carried out. 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. Further, if the annealing temperature exceeds 450°C, the crystal grains may coarsen and the adhesion of the Ni-P plating layer formed in the subsequent process may decrease. If the annealing time exceeds 10 hours, the manufacturing time may become long and there is a risk of productivity decline.

[0046] On the other hand, in continuous annealing, it is preferably carried out under the conditions of an annealing temperature of 400°C or higher and 500°C or lower for a holding time of 60 seconds or shorter. It is more preferably carried out under the conditions of an annealing temperature of 450°C or higher and 500°C or lower for a holding time of 30 seconds or shorter. If the annealing temperature is less than 400°C, a sufficient annealing effect may not be obtained. If the annealing temperature exceeds 500°C, the crystal grains may coarsen, and in the subsequent process, the adhesion of the Ni-P plating layer formed may decrease. Also, if the holding time exceeds 60 seconds, the crystal grains may coarsen, and in the subsequent process, the adhesion of the Ni-P plating layer formed may decrease. Note that cooling may be started immediately after reaching the desired annealing temperature.

[0047] By the above respective processes, an aluminum alloy plate is produced. Next, a magnetic disk is produced by performing the following processes on the produced aluminum alloy plate.

[0048] (g) A step of pressure 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 an annular shape to produce an annular disk blank. In one example, the annular disk blank is heated to 300°C in the atmosphere. At a temperature of 450 °C or lower for 30 minutes or more, preferably at a temperature of 300 °C or higher and 380 °C or lower for 6 0 minutes or more of pressure annealing is carried out to produce a flattened annular disk blank. If the processing temperature is less than 300 °C and / or the processing time is less than 30 minutes, the effect of flattening may not be sufficiently obtained . Also, if the processing temperature exceeds 450 °C, the crystal grains may coarsen, and the adhesion of the Ni-P plating layer formed in the subsequent process may decrease. The upper limit of the processing time is not particularly limited, but if it exceeds 24 hours, the manufacturing time may become long, leading to a decrease in productivity . Incidentally, the pressure in the pressure annealing is usually 0.1 MPa or more and 3.0 MPa or less .

[0049] (h) Step of subjecting the annular disk blank to cutting and grinding to obtain an aluminum alloy substrate for plating Next, the flattened annular disk blank is subjected to cutting and grinding in the cutting and grinding process. Then, optionally, at a temperature of 200 °C or higher and 290 °C or lower for 0.1 hour or more and 10 .0 hours or less, stress relief heat treatment for relieving the stress of the annular disk blank is performed

[0050] (i) Plating pretreatment step The aluminum alloy substrate for plating produced as described above is subjected to degreasing, etching, and zincate treatment (Zn replacement treatment) as plating pretreatment. Degreasing is performed, for example, using a commercially available AD -68F (manufactured by Uemura Kogyo Co., Ltd.) degreasing solution or the like, at a degreasing temperature of 40 °C or higher and 70 °C or lower, 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 under the conditions, preferably at a degreasing temperature of 45 °C or higher and 65 °C or lower, 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 When 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, sufficient degreasing effect may not be obtained. Also, when 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 decreases, and pits may occur after the plating process, resulting in a decrease in smoothness.

[0051] Etching is carried out, for example, using a commercially available AD-107F (manufactured by Uemura Kogyo Co., Ltd.) etching solution, etc., 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 a concentration of the etching solution of 20 mL / L or higher and 100 mL / L or lower. It is preferably carried out under the conditions of 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 a concentration of the etching solution of 40m L / L or higher and 100 mL / L or lower. When 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, sufficient etching effect may not be obtained. Also, when 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 decreases, and pits may occur after the plating process, resulting in a decrease in smoothness. Note that a normal desmatt treatment may be carried out between the etching treatment and the subsequent zincate treatment described below. .

[0052] The zincate treatment is carried out, for example, using a commercially available AD-301F-3X (manufactured by Uemura Kogyo Co., Ltd.) zincate treatment solution, etc., at a zincate treatment temperature of 10°C or higher and 35°C or lower, and a zincate treatment time of 0.1 minutes or longer and 5 minutes or shorter. The pickling treatment time, and the concentration of the pickling treatment solution of 100 mL / L or more and 500 mL / L or less It is preferably carried out under the conditions of a pickling treatment temperature of 15°C or more and 30°C or less, and a pickling treatment time of 0.1 minute or more and 2 minutes or less, and it is more preferably carried out under the conditions of a concentration of the pickling treatment solution of 200 mL / L or more and 400 mL / L or less. When the pickling treatment temperature is less than 10°C, the pickling treatment time is less than 0.1 minute, and / or the concentration of the pickling treatment solution is less than 100 mL / L, the pickling film becomes non-uniform, pits may occur after the plating treatment, and the smoothness may decrease . Also, when the pickling treatment temperature exceeds 35°C, the pickling treatment time exceeds 5 minutes, and / or the concentration of the pickling treatment solution exceeds 500 mL / L, the pickling film becomes non-uniform, pits may occur after the plating treatment, and the smoothness may decrease. (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 pickled aluminum alloy substrate for plating, and then polishing of its surface is carried out. The electroless Ni-P plating treatment

[0053] is preferably carried out, for example, using a commercially available Ni plating solution such as Nimden HDX (manufactured by Kamimura Kogyo Co., Ltd.) under the conditions of a plating treatment temperature of 80°C or more and 95°C or less, a plating treatment time of 30 minutes or more and 180 minutes or less, and a Ni concentration in the plating solution of 3 g / L or more and 10 g / L or less. It is more preferably carried out under the conditions of a plating treatment temperature of 85°C or more and 95°C or less, a plating treatment time of 60 minutes or more and 120 minutes or less, and a Ni concentration in the plating solution of 4 g / L or more and 9 g / L or less. In addition, as described above, Ni deposited on the surface of the counter electrode in the film removal step, and the acidic solution containing Ni after anodic electrolysis are recovered, and these Ni and the acidic solution containing Ni are used as the plating solution . ​​​​​​ It may be added. If the plating temperature is less than 80 °C and / or the Ni concentration in the plating solution is less than 3 g / L, the growth rate of the plating is slow, which may lead to a decrease in productivity. Also, if the plating time is less than 30 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, if the plating temperature exceeds 95 °C and / or the Ni concentration in the plating solution exceeds 10 g / L, the plating grows unevenly, so the smoothness of the plating may be low and decrease. Also, if the plating time exceeds 180 minutes, the manufacturing time becomes long, which may lead to a decrease in productivity. Furthermore, the surface of the underlying (Ni-P) plating is subjected to a polishing treatment. By these pre-plating treatments and the underlying (Ni-P) plating treatment (with polishing), an aluminum alloy substrate for a magnetic disk is produced.

[0054] (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.

[0055] 4. Magnetic Disk The magnetic disk of the present invention can be manufactured 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 formed on the Ni-P plating layer It has a formed magnetic layer. Also, a protective layer or a lubricating layer may be formed on the magnetic layer. Such a magnetic disk of the present invention is produced by using the above-described recycled material, and thus is beneficial as a magnetic disk excellent in reducing environmental load.

[0056] 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, a clamp member for fixing the inner diameter side portion of the magnetic disk, a magnetic head for performing data processing on the magnetic disk, an actuator for movably supporting the magnetic head with respect to the magnetic disk, and a swing arm for rotating and positioning the actuator. Such a hard disk drive of the present invention is produced by using the above-described recycled material, and thus is excellent in reducing environmental load. 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 making many of the magnetic disks in such a hard disk drive using the recycled material, it is possible to make it particularly excellent in reducing environmental load.

[0057] Based on the above embodiments, the present invention relates to the following [1] to [8]. [1] A method for recycling an aluminum alloy substrate, comprising a film removing step of obtaining an aluminum alloy material by removing a film from a recycled material by immersing the recycled material having an aluminum alloy substrate and at least one layer of a film containing Ni on the aluminum alloy substrate in a solution and applying electricity to the recycled material. [2] The solution is an acidic solution containing sulfate ions, and is the aluminum alloy base described in the above [1]. Recycling method of the plate. [3] The acidic solution has a temperature of 20 °C or higher and a sulfate ion concentration of 5% by mass or more, In the film removal step, the film is removed by performing anodic electrolysis in a state where the recycled material and the counter electrode immersed in the acidic solution are electrically connected to each other. The recycling method of the aluminum alloy substrate described in the above 2].[[]] Recycling method of the aluminum alloy substrate described in [2].[[]] [4] Furthermore, in the film removal step, a step of recovering Ni deposited on the surface of the counter electrode and the acidic solution containing Ni after anodic electrolysis is provided. The aluminum described in the above [3].[[]] Recycling method of the alloy substrate.[[]] Recycling method of the aluminum alloy substrate described in [3].[[]] [5] The aluminum alloy substrate constituting the recycled material is annular, and is the recycling method of the aluminum alloy substrate described in any one of the above [1] to [4 . [6] By the recycling method of the aluminum alloy substrate described in any one of the above [1] to [5], A step of preparing a molten aluminum alloy using at least a part of the obtained aluminum alloy material as a raw material, A step of heating and holding the prepared molten metal, A step of heating and holding the molten metal to obtain an aluminum alloy ingot by casting, A step of heating the aluminum alloy ingot to perform a homogenization treatment, A rolling step of rolling the homogenized aluminum alloy ingot into an aluminum alloy plate, And a step of pressing and flattening the aluminum alloy plate obtained by the rolling step into an annular disk blank, And, A step of subjecting the annular disk blank that has been pressed and flattened to cutting and grinding to obtain an aluminum for plating, And a step of, A step of subjecting the annular disk blank that has been pressed and flattened to cutting and grinding to obtain an aluminum for plating, The step of obtaining a niobium alloy substrate, The step of performing degreasing, etching, and zincate treatment on the aluminum alloy substrate for plating The pre-plating treatment step, After performing electroless Ni-P plating treatment on the surface of the aluminum alloy substrate subjected to pre-plating treatment, the surface subjected to Ni-P plating treatment is polished to obtain an aluminum alloy substrate for a magnetic disk The step of obtaining, The step of forming a magnetic layer by adhering a magnetic material to the surface of the aluminum alloy substrate for a magnetic disk The step of forming, A method for manufacturing a magnetic disk having [7] A magnetic disk obtained by the method for manufacturing a magnetic disk according to [6] above. [8] A hard disk drive including the magnetic disk according to [7] above.

[0058] As described above, the recycling method of the aluminum alloy substrate, the manufacturing method of the magnetic disk, the magnetic disk, and the hard disk drive according to the present embodiment have been described. However, the present invention is not limited to the above embodiment, and various modifications and changes are possible based on the technical idea of the present invention.

Example

[0059] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[0060] (Examples 1 to 3) As a recycled material, an aluminum alloy substrate made of JIS 5086 alloy (Al-Mg alloy), and a Ni-P plating layer (film) formed on the aluminum alloy substrate by electroless Ni-P plating treatment, an aluminum alloy substrate for a magnetic disk (outer diameter 95 mm, inner diameter 25 mm, and overall thickness 1.3 mm) was used as the test material. Based on the aluminum alloy The composition of the aluminum alloy used for the aluminum alloy plate 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, and the balance was Al , consisting of inevitable impurities and trace components. Cut out from the test material to a size of 20 mm × 45 mm , and masking was performed leaving the upper clip gripping margin and the lower peeling target part of 10 mm × 10 mm . The masked samples were used as the samples for each example.

[0061] The samples for each example were electrically connected to the positive electrode of the power supply, and a Pt wire was used as the counter electrode The negative electrode of the power supply was electrically connected to the counter electrode, and the sample and the counter electrode were immersed in an acidic solution to fabricate an anodic electrolysis device as shown in Fig. 1. The composition of the acidic solution and the voltage applied between the sample and the counter electrode during anodic electrolysis were set to the conditions shown in Table 1 below. Note , the composition of the acidic solution consisted of sulfuric acid and pure water, and the content of pure water was 90% by mass. Also , through a preliminary test in advance, the change over time of the current density flowing between the sample and the counter electrode during anodic electrolysis was measured, and (1) At the initial stage of anodic electrolysis, a constant current density was obtained, (2) As the removal of the Ni-P plating layer (film) progressed, the current density decreased rapidly, (3) When the removal of the Ni-P plating layer (film) was completed and the aluminum alloy substrate was exposed and the anodic oxide film of the aluminum alloy substrate was formed, a constant current density much lower than the constant current at the initial stage of anodic electrolysis was obtained, which was confirmed. Therefore, in each example, the change over time of the current density flowing between the sample and the counter electrode during anodic electrolysis was measured, and the time when the state of (3) above was first manifested was defined as the film formation time. The current density became a constant value much lower than the constant current at the initial stage of anodic electrolysis. For this reason, in each example, the change over time of the current density flowing between the sample and the counter electrode during anodic electrolysis was measured, and the time when the state of (3) above was first manifested was defined as the film formation time. It was measured as the "peeling time" when the removal was completed. FIG. 2 is a graph showing the change over time of the current density during anodic electrolysis in Example 1. In FIG. 2, the start time of anodic electrolysis is set as 0 seconds. As shown in FIG. 2, in Example 1, the current density started to decrease at around 80 seconds after the start of anodic electrolysis and became a low constant current density after 125 seconds had elapsed. Therefore, the peeling time was set as 125 seconds. The "peeling time" measured in each example is shown in Table 1 below. FIG. 2 is a graph showing the change over time of the current density during anodic electrolysis in Example 1. In FIG. 2, the start time of anodic electrolysis is set as 0 seconds. As shown in FIG. 2, in Example 1, the current density started to decrease at around 80 seconds after the start of anodic electrolysis and became a low constant current density after 125 seconds had elapsed. Therefore, the peeling time was set as 125 seconds. The "peeling time" measured in each example is shown in Table 1 below.

[0062] (Comparative Examples 1 and 2) The composition of the acidic solution was as shown in Table 1 below, and the sample was immersed in the acidic solution without performing anodic electrolysis. The composition of the acidic solution consisted of sulfuric acid or hydrochloric acid and pure water, and the content of pure water was 90 mass%. Also, in Comparative Examples 1 and 2, no voltage was applied to the sample, so it was visually confirmed whether the Ni-P plating layer (film) was removed or not. In Comparative Examples 1 and 2, after the sample was immersed in the acidic solution, it was confirmed that the Ni-P plating layer (film) remained even after 60 minutes had elapsed. Therefore, in Table 1 below, the peeling times of Comparative Examples 1 and 2 are shown as "-". The composition of the acidic solution consisted of sulfuric acid or hydrochloric acid and pure water, and the content of pure water was 90 mass%. Also, in Comparative Examples 1 and 2, no voltage was applied to the sample, so it was visually confirmed whether the Ni-P plating layer (film) was removed or not. In Comparative Examples 1 and 2, after the sample was immersed in the acidic solution, it was confirmed that the Ni-P plating layer (film) remained even after 60 minutes had elapsed. Therefore, in Table 1 below, the peeling times of Comparative Examples 1 and 2 are shown as "-". In Comparative Examples 1 and 2, after the sample was immersed in the acidic solution, it was confirmed that the Ni-P plating layer (film) remained even after 60 minutes had elapsed. Therefore, in Table 1 below, the peeling times of Comparative Examples 1 and 2 are shown as "-". In Comparative Examples 1 and 2, after the sample was immersed in the acidic solution, it was confirmed that the Ni-P plating layer (film) remained even after 60 minutes had elapsed. Therefore, in Table 1 below, the peeling times of Comparative Examples 1 and 2 are shown as "-". In Comparative Examples 1 and 2, after the sample was immersed in the acidic solution, it was confirmed that the Ni-P plating layer (film) remained even after 60 minutes had elapsed. Therefore, in Table 1 below, the peeling times of Comparative Examples 1 and 2 are shown as "-".

[0063]

Table 1

[0064] As shown in Examples 1 to 3 in Table 1, the peeling time was the shortest in Example 1 where the voltage during anodic electrolysis was the highest, and the peeling time was the longest in Example 3 where the voltage during anodic electrolysis was the lowest. From this, it can be understood that the effect of removing the film is high when the voltage during anodic electrolysis is 2V. Also, in Comparative Examples 1 to 2, since anodic electrolysis was not performed, the Ni-P plating layer (film) As shown in Examples 1 to 3 in Table 1, the peeling time was the shortest in Example 1 where the voltage during anodic electrolysis was the highest, and the peeling time was the longest in Example 3 where the voltage during anodic electrolysis was the lowest. From this, it can be understood that the effect of removing the film is high when the voltage during anodic electrolysis is 2V. From this, it can be understood that the effect of removing the film is high when the voltage during anodic electrolysis is 2V. Also, in Comparative Examples 1 to 2, since anodic electrolysis was not performed, the Ni-P plating layer (film) From this, it can be understood that the effect of removing the film is high when the voltage during anodic electrolysis is 2V. Also, in Comparative Examples 1 to 2, since anodic electrolysis was not performed, the Ni-P plating layer (film) ​​The (film) could not be removed. As described above, in the recycling method of the aluminum alloy substrate of the present invention the Ni-P plating layer (film) can be efficiently removed, and it was confirmed that the recycling method is excellent in recyclability.

Industrial Applicability

[0065] The present invention can provide a recycling method for an aluminum alloy substrate with excellent recyclability that can be achieved.

Explanation of Reference Numerals

[0066] 1 Anode electrolysis device 2 Ni-P plating layer (film) 3 Aluminum alloy substrate 4 Counter electrode 5 Power supply 6 Acidic solution 7 Anodized film

Claims

1. A recycling method for an aluminum alloy substrate, comprising a step of removing a film from a recycling material having an aluminum alloy substrate and at least one layer of a film containing Ni on the aluminum alloy substrate by immersing the recycling material in a solution and applying an electric current to the recycling material. While the recycling material having an aluminum alloy substrate and at least one layer of a film containing Ni on the aluminum alloy substrate is immersed in a solution, an electric current is applied to the recycling material to remove the film from the recycling material and obtain an aluminum alloy material. Film removal step to obtain an aluminum alloy material by removing the film from the recycling material.

2. The recycling method for an aluminum alloy substrate according to claim 1, wherein the solution is an acidic solution containing sulfate ions.

3. The acidic solution has a temperature of 20°C or higher and a sulfate ion concentration of 5% by mass or more. In the film removal step, anodic electrolysis is performed with the recycling material and a counter electrode immersed in the acidic solution electrically connected to remove the film. In the film removal step, the film is removed by performing anodic electrolysis with the recycling material and a counter electrode immersed in the acidic solution electrically connected. The recycling method for an aluminum alloy substrate according to claim 2.

4. Further, the recycling method for an aluminum alloy substrate according to claim 3 includes a step of recovering Ni deposited on the surface of the counter electrode and an acidic solution containing Ni after anodic electrolysis in the film removal step. The recycling method for an aluminum alloy substrate according to claim 3, further comprising a step of recovering Ni deposited on the surface of the counter electrode and an acidic solution containing Ni after anodic electrolysis in the film removal step.

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

6. A step of preparing a molten aluminum alloy using at least a part of the aluminum alloy material obtained by the recycling method for an aluminum alloy substrate according to claim 1 or 2 as a raw material, A step of heating and holding the prepared molten metal, A step of casting the molten metal kept heated to obtain an aluminum alloy ingot, A step of heating the aluminum alloy ingot to perform a homogenization treatment, A rolling step of rolling the aluminum alloy ingot subjected to the homogenization treatment into an aluminum alloy plate and, A step of pressing and flattening the aluminum alloy plate obtained by the rolling step into an annular disk blank ; A step of performing cutting and grinding on the pressed and flattened annular disk blank to obtain an aluminum alloy substrate for plating ; A plating pretreatment step of subjecting the aluminum alloy substrate for plating to degreasing, etching, and zincating treatments ; A step of performing electroless Ni-P plating on the surface of the aluminum alloy substrate subjected to the plating pretreatment, and then polishing the surface subjected to the Ni-P plating to obtain an aluminum alloy substrate for a magnetic disk ; A step of forming a magnetic layer by adhering a magnetic material to the surface of the aluminum alloy substrate for the magnetic disk ; and a method for manufacturing a magnetic disk having . A method for manufacturing a magnetic disk.

7. A magnetic disk obtained by the method for manufacturing a magnetic disk according to Claim 6.

8. A hard disk drive including the magnetic disk according to Claim 7.

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