Aluminum alloy disk material, method for producing aluminum alloy raw material, method for producing aluminum alloy ingot, method for producing aluminum alloy plate, method for producing aluminum alloy substrate for plating, method for producing aluminum alloy substrate for magnetic disk, and method for producing magnetic disk, and magnetic disk

Abstract

To provide an aluminum alloy disk material, a method for producing an aluminum alloy raw material, a method for producing an aluminum alloy ingot, a method for producing an aluminum alloy plate, a method for producing an aluminum alloy substrate for plating, a method for producing an aluminum alloy substrate for a magnetic disk, a method for producing a magnetic disk, and a magnetic disk.SOLUTION: An aluminum alloy disc material has a peeling surface obtained by peeling, from at least either of recycled materials of an intermediate material and a finished product including an aluminum alloy disc 1 and a base layer containing Ni, wherein an oxide film 10 is provided on a surface of the peeling surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an aluminum alloy disk material, a method for producing an aluminum alloy raw material, a method for producing an aluminum alloy ingot, a method for producing an aluminum alloy plate, a method for producing an aluminum alloy substrate for plating, a method for producing an aluminum alloy substrate for magnetic disks, a method for producing a magnetic disk, and a magnetic disk obtained by the method, all of which are highly recyclable. [Background technology]

[0002] Aluminum alloy magnetic disks used in computer storage devices are manufactured from aluminum alloy substrates based on JIS 5086 series aluminum alloys, which have good plating properties as well as excellent mechanical properties and workability.

[0003] Furthermore, aluminum alloy magnetic disks are manufactured from aluminum alloy substrates in which the content of impurities in JIS 5086 aluminum alloys, such as Fe, Si, Mn, is limited and the size of the intermetallic compounds in the matrix is ​​reduced in order to improve pit defects caused by the loss of intermetallic compounds in the plating pretreatment process, or from aluminum alloy substrates in which Cu and Zn are intentionally added to the JIS 5086 aluminum alloy in order to improve plating properties.

[0004] In the general manufacturing of aluminum alloy magnetic disks, an aluminum alloy plate is first produced, then an annular aluminum alloy disk blank is produced, which is then cut and ground, and then pressure annealed to produce an aluminum alloy substrate. Next, this aluminum alloy substrate is plated, and a magnetic material is attached to the surface of the aluminum alloy substrate to produce an aluminum alloy magnetic disk.

[0005] For example, an aluminum alloy magnetic disk using a JIS 5086 aluminum alloy is manufactured by the following manufacturing process. First, an aluminum alloy having a desired alloy composition is cast, and the ingot is hot rolled and then cold rolled to produce a rolled material having a thickness required for a magnetic disk. This rolled material is annealed during the cold rolling as necessary. Next, this rolled material is punched into an annular shape, and further, in order to remove distortions and the like caused during the manufacturing process, annular aluminum alloy plates are stacked, and pressure annealing is performed to flatten the stack while applying pressure from both sides. Through these steps, a disk blank is manufactured.

[0006] The disk blank thus produced is subjected to cutting and grinding as pretreatment, and then heat-treated to remove distortions and other defects caused by the processing steps, producing an aluminum alloy substrate. Next, degreasing, etching, and zincate treatment (Zn substitution treatment) are performed as pretreatment for plating, and Ni-P plating, a hard non-magnetic metal, is applied as a base treatment, and the surface is polished to produce an aluminum alloy substrate for a magnetic disk. Finally, a magnetic disk made of an aluminum alloy is produced by sputtering a magnetic material, etc.

[0007] In recent years, magnetic disks are required to have larger capacity and higher density due to the needs of multimedia, etc. In order to achieve further capacity, the number of magnetic disks mounted in storage devices is increasing, and accordingly, the magnetic disks are required to be thinner. However, when the thickness of the aluminum alloy substrate for magnetic disks is reduced, the rigidity is reduced, so the aluminum alloy substrate is required to have higher rigidity, and in recent years, high-rigidity materials with added Ni, etc. have been investigated.

[0008] On the other hand, as the number of magnetic disks mounted increases, the amount of aluminum and other materials required, which are the raw materials for the aluminum alloy substrates used in magnetic disks, is also increasing. However, because these resources are limited, there is a demand to reuse aluminum alloy substrates and magnetic disks that have plating or magnetic materials attached to them as part of the raw materials for aluminum alloy materials. For aluminum alloy substrates, those that have defects and are unsuitable for use as products are used, and for magnetic disks, defective products and those extracted from used HDDs are used.

[0009] In view of this situation, in recent years, there has been a strong demand for and studies have been made on a method for manufacturing an aluminum alloy ingot with excellent recyclability, a method for manufacturing an aluminum alloy plate using the ingot, a method for manufacturing an aluminum alloy substrate for magnetic disks using the aluminum alloy plate, and a method for manufacturing a magnetic disk using the aluminum alloy substrate. For example, Patent Document 1 proposes that by making an aluminum alloy for magnetic disks contain Ni, the aluminum alloy substrate can be reused as a raw material.

[0010] However, in the method disclosed in Patent Document 1, when a large amount of aluminum alloy substrates for magnetic disks are used as raw materials, for example, when the aluminum alloy substrates for magnetic disks account for 50% or more of the raw materials by weight, the aluminum alloy raw materials may contain 3.0% or more by mass of Ni. Therefore, when producing an aluminum alloy raw material that cannot tolerate a large amount of Ni, only a small amount of aluminum alloy substrates for magnetic disks can be used, and there is a concern that recyclability may be lacking. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2002-275568 A Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide an aluminum alloy disk material, a method for producing an aluminum alloy raw material, a method for producing an aluminum alloy ingot, a method for producing an aluminum alloy plate, a method for producing an aluminum alloy substrate for plating, a method for producing an aluminum alloy substrate for magnetic disks, a method for producing a magnetic disk, and a magnetic disk, all of which are highly recyclable. [Means for solving the problem]

[0013] The present inventors have discovered that when separating an aluminum alloy disk and an underlayer from an intermediate material or a finished product to be recycled, by promoting the formation of an oxide film on the surface of the aluminum alloy disk material obtained by separating the underlayer, an aluminum alloy disk material and an aluminum alloy raw material with excellent recyclability can be obtained, and have completed the present invention.

[0014] The aluminum alloy disk material according to an embodiment of the present invention is an aluminum alloy disk material having a peeled surface formed by peeling off the base layer from at least one of a recycled material of an intermediate material and a finished product comprising an aluminum alloy disk and a base layer containing Ni, and has an oxide film on the surface of the peeled surface.

[0015] A method for producing an aluminum alloy raw material according to an embodiment of the present invention includes a separation step of reusing at least one of an intermediate material and a finished product comprising an aluminum alloy disk and a Ni-containing underlayer as a recycled material for at least a part of an aluminum alloy material, and separating the aluminum alloy disk and the underlayer by heating or wet treating the aluminum alloy material containing the recycled material, and an oxide film is formed on the peeled surface of the aluminum alloy disk material obtained by peeling off the underlayer. Effect of the Invention

[0016] According to the present invention, it is possible to provide an aluminum alloy disk material, a method for producing an aluminum alloy raw material, a method for producing an aluminum alloy ingot, a method for producing an aluminum alloy plate, a method for producing an aluminum alloy substrate for plating, a method for producing an aluminum alloy substrate for magnetic disks, a method for producing a magnetic disk, and a magnetic disk, all of which are excellent in recyclability. [Brief description of the drawings]

[0017] [Figure 1] 1 shows a schematic diagram of an aluminum alloy disk material according to the present invention. [Diagram 2] FIG. 1 is a flow diagram showing a process for producing an aluminum alloy raw material according to the present invention through a process for producing a magnetic disk. [Figure 3A] 1 shows the results of quantitative elemental analysis by GDS for the aluminum alloy disk material produced in Example 1. [Figure 3B] FIG. 3A shows the results of quantitative elemental analysis in an expanded range where the sputtering time was short. [Figure 4A] 1 shows the results of quantitative elemental analysis by GDS for the aluminum alloy disk material produced in Example 5. [Figure 4B] FIG. 4A shows the results of quantitative elemental analysis in an expanded range where the sputtering time was short. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] 1.Aluminum alloy disc material As shown in FIG. 1, the aluminum alloy disk material 1 in the present invention has a peeled surface where the underlayer is peeled off from at least one of the recycled materials, which are an intermediate material and a finished product having an aluminum alloy disk and an underlayer containing Ni, and has an oxide film 10 on the surface of the peeled surface. Since the oxide film 10 is formed on the surface of the aluminum alloy disk material 1, when the aluminum alloy disk material 1 is reused to produce an aluminum alloy raw material and then used to newly produce an aluminum alloy ingot, the peeled surface having the oxide film 10 is further melted in a molten metal heating and holding step described later, and the oxide film 10 is peeled off partially or entirely from the aluminum alloy disk material 1 and floats to the surface of the molten metal. By removing the oxide film 10 that has floated to the surface of the molten metal, it is possible to reduce the plating remaining on the surface (peeled surface) of the aluminum alloy disk material 1, and an aluminum alloy disk material with excellent recyclability can be obtained. The formation of the oxide film 10 can be confirmed, for example, by using glow discharge optical emission spectroscopy (hereinafter referred to as "GDS"). When a peak in the luminous intensity of oxygen (O) is observed, it can be determined that the oxide film 10 has been formed.

[0020] Here, the recycled material used in the present invention is an aluminum alloy disk having a base layer such as a Ni-P plating layer, an intermediate material is an aluminum alloy substrate for a magnetic disk, and a finished product is a magnetic disk. These recycled materials are defective products, non-standard products, and used magnetic disks.

[0021] 2.Recycled materials First, an aluminum alloy substrate for magnetic disks and a magnetic disk as recycled materials used as at least a part of an aluminum alloy material in the production of an aluminum alloy raw material (hereinafter also referred to as "aluminum alloy raw material" or simply "alloy raw material") will be described. Moreover, "at least a part" means that the entire aluminum alloy material may be these recycled materials, or that only a part of the aluminum alloy material may be these recycled materials.

[0022] 2-1. Aluminum alloy substrates for magnetic disks: (intermediate material) Since an underlayer containing Ni, such as a Ni-P plating layer, is formed on the surface of the aluminum alloy substrate for magnetic disks, it is important to separate most of the underlayer in order to add it to at least a part of an aluminum alloy material that does not contain much Ni. The Ni content in the underlayer containing Ni used in the aluminum alloy substrate for magnetic disks is, for example, 80% by mass or more and 95% by mass or less. In addition, when the underlayer containing Ni is a Ni-P plating layer, the P content in the Ni-P plating layer is, for example, 5% by mass or more and 20% by mass or less. In addition, the thickness of the underlayer containing Ni is not particularly limited, but is, for example, 3 μm or more and 25 μm or less, and the thickness of the aluminum alloy substrate for magnetic disks is, for example, 0.3 mm or more and 2.0 mm or less.

[0023] 2-2. Magnetic disk: (finished product) In the magnetic disk, a CoCrPt-based magnetic layer or a protective film of a carbon-based material is formed on the surface of the above-mentioned aluminum alloy substrate for magnetic disk, but since these magnetic layers and protective films are formed on the underlayer, most of them can be removed by removing the underlayer. Therefore, the magnetic disk from which the underlayer is separated can also be used for at least a part of an aluminum alloy material that does not contain a large amount of Ni or P. It is important to remove a large amount of the underlayer when using the magnetic disk as an aluminum alloy material, just like the aluminum alloy substrate for magnetic disk.

[0024] 2-3.Aluminum alloy material The aluminum alloy material is a general material adjusted to have a predetermined alloy composition and used as a raw material for producing an aluminum alloy ingot. The aluminum alloy raw material produced in the present invention includes an embodiment including such an aluminum alloy material and an aluminum alloy disk material separated from a recycled material, and an embodiment not including an aluminum alloy material but being the aluminum alloy disk material itself separated from a recycled material.

[0025] 2-4.Oxide film The oxide film formed on the surface of the aluminum alloy disk material contains at least one of S (sulfur) and P (phosphorus). Of these elements, S is contained in the oxide film due to sulfuric acid used when performing wet treatment in the separation process as described later. On the other hand, P is contained in the oxide film due to the plating layer, so that an oxide (slag) containing at least one of S (sulfur) and P (phosphorus) is present on the surface (peeling surface) of the aluminum alloy disk material. This oxide is formed as an oxide film on the peeling surface of the aluminum alloy disk material by the separation process of separating the aluminum alloy disk and the undercoat layer described later. The thickness of the oxide film is not particularly limited, but is preferably 0.01 μm to 10 μm, more preferably 0.02 μm to 5 μm.

[0026] Next, a detailed description will be given of a method for producing an aluminum alloy raw material according to an embodiment of the present invention, a method for producing an aluminum alloy ingot using this aluminum alloy raw material, a method for producing an aluminum alloy plate using this aluminum alloy ingot, a method for producing an aluminum alloy substrate for plating using this aluminum alloy plate, a method for producing an aluminum alloy substrate for magnetic disks using this aluminum alloy substrate for plating, a magnetic disk using this aluminum alloy substrate for magnetic disks, and a magnetic disk obtained by the manufacturing method.

[0027] 3. Manufacturing method of aluminum alloy raw materials The method for producing an aluminum alloy raw material in the present invention includes a separation step in which at least one of an intermediate material and a finished product comprising an aluminum alloy disk and an underlayer containing Ni is reused as a recycled material for at least a part of an aluminum alloy raw material, and the aluminum alloy disk and the underlayer are separated by heating or wet treating the aluminum alloy raw material containing the recycled material. By such a separation step, an oxide film is formed on the peeled surface of the aluminum alloy disk material obtained by peeling off the underlayer, and in the subsequent molten metal heating and holding step, the underlayer remaining on the peeled surface of the aluminum alloy disk material can be further separated, thereby obtaining an aluminum alloy raw material with excellent recyclability.

[0028] Fig. 2 is a flow chart showing each process from the manufacturing method of aluminum alloy raw material to the production of a magnetic disk. As shown in Fig. 2, the aluminum alloy raw material is manufactured through a process of separating the underlayer (step S101). As a method for separating the underlayer, a mechanical process for physically separating the underlayer, a dry process such as heating, a wet process such as chemical dissolution, etc. are conventionally known. Here, separation by heating and separation by chemical dissolution will be described.

[0029] In step S101, an intermediate material (aluminum alloy substrate for magnetic disk) or a finished product (magnetic disk) is used as at least a part of the aluminum alloy material as the recycled material, and the aluminum alloy disk and the underlayer are separated from the recycled material by heating or wet processing (step S101).

[0030] In such a separation step, when the aluminum alloy disk and the underlayer are separated from the recycled material by heating, in step S101, it is preferable to heat and hold the aluminum alloy material containing the recycled material at 480°C or more and 570°C or less for more than 1 hour. By heating, the Ni-P plating contained in the underlayer reacts with the aluminum in the aluminum alloy disk, and a brittle intermediate layer containing Al, Ni and P is formed between the underlayer and the aluminum alloy disk. As a result, cracks are generated starting from the intermediate layer containing Al, Ni and P due to thermal stress during cooling after heating, and the underlayer can be separated. In the separation step, if the heating temperature is less than 480°C and / or the holding time is less than 1 hour, the above separation effect cannot be obtained. In addition, it is insufficient from the viewpoint of formation of an oxide film. On the other hand, if the heating temperature exceeds 570°C, a part of the aluminum alloy disk melts, making it difficult to peel off the underlayer.

[0031] From the viewpoint of separation, the heating temperature is more preferably 520°C or more and 570°C or less, and the holding time is more preferably 2 hours or more. By holding the heating in this manner, the separation of the aluminum alloy disk and the undercoat layer can be promoted, and the oxide film on the surface can be made thicker. The upper limit of the holding time is not particularly limited, but from the economic viewpoint, it is preferably 30 hours.

[0032] In the separation step, it is preferable to perform a cooling step of cooling the aluminum alloy material containing the recycled material to room temperature after heating multiple times. By performing cooling multiple times, the separability can be improved, and a thicker oxide film can be formed on the surface of the aluminum disk material. The number of cooling steps is preferably two or more, more preferably three or more. In addition, in the cooling step, it is preferable to cool at a cooling rate of 30°C / h or more in a temperature range of 400 to 450°C. As described above, the Ni-P plating contained in the underlayer is cracked and separated from the intermediate layer containing Al, Ni and P due to thermal stress generated during cooling, but if the cooling rate in the above-mentioned temperature range is slow, the thermal stress is small and separation may be insufficient. Therefore, when cooling to room temperature after heating, the cooling rate in the temperature range of 400 to 450°C is preferably 30°C / h or more, more preferably 50°C / h or more, and even more preferably 80°C / h or more. In addition, room temperature means a range of -10 to 50°C.

[0033] In the cooling step, it is preferable to further apply a physical impact to the aluminum alloy material containing the recycled material. By applying an impact to the recycled material, cracks in the intermediate layer containing Al, Ni, and P are likely to progress, and the underlayer is likely to peel off. Methods for applying an impact include a method of dropping the recycled material as the target object, and a method of mechanically moving the target object to contact with another object, but are not limited to these methods, and an impact can be applied to the aluminum alloy material containing the recycled material by any method.

[0034] In the separation step, the heating rate when heating to a predetermined temperature is not particularly limited, but is preferably 30° C. / h or more, more preferably 50° C. / h or more, and even more preferably 80° C. / h or more. The aluminum alloy material containing the recycled material may be directly charged into a furnace that has been heated to a predetermined temperature in advance.

[0035] Next, separation by wet processing will be described. When the aluminum alloy disk and the underlayer are separated from the recycled material by chemical dissolution, for example, sulfuric acid electrolysis, in step S101, it is preferable to electrolyze the aluminum alloy material containing the recycled material with sulfuric acid. The concentration of sulfuric acid in the electrolyte used for sulfuric acid electrolysis is preferably 10 g / L or more and 200 g / L or less (10 g or more and 200 g or less of 98% sulfuric acid per 1 L of water), and more preferably 50 g / L or more and 150 g / L or less. If the concentration of sulfuric acid is less than 10 g / L, the dissolution of the underlayer is difficult to proceed, while if the concentration of sulfuric acid exceeds 200 g / L, the viscosity of the electrolyte increases and the dissolution rate decreases, which is inefficient. In addition, the temperature of the electrolyte is preferably 5°C or more and 50°C or less. If the temperature is less than 5°C, the current efficiency is low and the efficiency decreases, and if the temperature exceeds 50°C, hydrogen generation during electrolysis becomes intense, which is undesirable from the standpoint of safety. In addition, the processing time of sulfuric acid electrolysis is preferably 30 seconds or more and 1200 seconds or less. If the treatment time is less than 30 seconds, the formation of the oxide film is insufficient, and if it exceeds 1200 seconds, it is not preferable from the viewpoint of productivity. In addition, the voltage applied in sulfuric acid electrolysis is preferably 0.1 V or more and 30 V or less. If the voltage is less than 0.1 V, the dissolution rate becomes slow, and if it exceeds 30 V, hydrogen generation during electrolysis becomes intense, which is not preferable from the viewpoint of safety.

[0036] In addition, when quantitative elemental analysis is performed on the aluminum alloy disk material obtained after the separation step in the depth direction from the surface of the oxide film by glow discharge optical emission spectroscopy (GD-OES), it is preferable that the time for the peak of the emission intensity of oxygen (O) to become half is 0.1 seconds or more. Although the above-mentioned separation method can remove a certain amount of the underlayer from the aluminum alloy disk material, a part of the underlayer remains on the surface of the aluminum alloy disk material. In order to further remove this underlayer, it is preferable to thicken the above-mentioned oxide film formed on the surface (peeling surface) of the aluminum alloy disk material. By thickening the oxide film, the remaining underlayer is easily separated from the peeling surface of the aluminum alloy disk material together with the oxide film. Specifically, in the molten metal holding step described later, the oxide film present on the peeling surface is completely separated and floats to the surface of the molten metal, so that the underlayer can be further removed by removing it. Since the time taken for the oxygen (O) emission intensity peak to reach half its peak is 0.1 seconds or more, a thick oxide film is formed, and the remaining underlayer is easily separated from the peeled surface of the aluminum alloy disk material together with the oxide film. In addition, since this oxide film is partially porous, it is easy for it to float to the surface of the molten metal, but in order to lower the density and make it easier to float, it is preferable that the oxide film contains at least one of S and P, which have a lower density than Al.

[0037] Through the above steps, an aluminum alloy raw material for magnetic disks is produced.

[0038] 4. Manufacturing method of aluminum alloy ingot The method for producing an aluminum alloy ingot includes a molten metal preparation step of preparing a molten aluminum alloy using at least a part of the aluminum alloy raw material obtained by the above-mentioned production method, a molten metal heating and holding step of heating and holding the prepared molten metal, and a casting step of casting the heated and held molten metal. Specifically, the aluminum alloy ingot is produced through the steps of adjusting the aluminum alloy components, preparing and heating and holding the molten aluminum alloy (step S102), and casting the aluminum alloy (step S103), as shown in Fig. 2.

[0039] 4-1. Adjustment of aluminum alloy composition and heating and holding the molten metal (Step S102) In step S102, a molten aluminum alloy having a predetermined alloy composition is prepared by heating and melting the aluminum alloy raw material including the aluminum alloy disk material separated from the recycled material in step S101 in a conventional manner.

[0040] Ni (nickel) content In the molten metal heating and holding step, 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) and the like to form Al-Ni compounds, which cause major defects on the plating surface, so the Ni content needs to be reduced. 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 Ni content is adjusted in the aluminum alloy component adjustment step in which the raw materials are heated and melted. For example, the components of the molten metal are analyzed after the raw materials in the molten metal are completely melted, and if the Ni content is high, aluminum ingot or the like is added to adjust the Ni content to the desired content.

[0041] ·P (phosphorus) content In the molten metal heating and holding step, the P content in the molten aluminum alloy is preferably 0% by mass or more and 0.05% by mass or less. P is contained as a plating component partially remaining in the recycled material or in the aluminum alloy ingot, but it combines with Mg (magnesium) generally contained in the aluminum alloy raw material of the molten metal to generate Mg-P-based oxides, and during the plating process, the reaction becomes uneven only in that part, and large defects may occur on the plating surface. As a result, the smoothness of the plating surface decreases. Note that, although some of the Mg-P-based oxides can be removed 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 the P content to a desired content by adding aluminum ingots, etc. However, if adjustment is necessary, the content is adjusted to a desired content by adding aluminum ingots, etc., in the same way as Ni.

[0042] ·Mg (Magnesium) content In the molten metal heating and holding step, the Mg content in the molten aluminum alloy is preferably 0% by mass or more and 6.5% by mass or less. As described above, Mg combines with P in the molten metal to produce Mg-P-based oxides, so its content is preferably low, similar to 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. If the Mg content is high, aluminum ingot or the like is added to adjust the content to the desired level, similar to Ni.

[0043] Metallic components in molten aluminum alloys Regarding the metal components contained in the molten aluminum alloy, in order to effectively remove or reduce the P components derived from the electroless Ni-P plating components contained in the aluminum alloy substrate for magnetic disks, which are recycled materials, and in the magnetic disks, it is preferable to adjust the content of P itself and elements such as Cu and Mg that form intermetallic compounds with P, as described above.

[0044] On the other hand, elements other than Ni, P, Cu, and Mg and their contents are not particularly limited. Examples of alloy compositions contained in the molten aluminum alloy include the following. The aluminum alloy contains an essential element Fe (iron) and optionally Mn (manganese), with the total content of Fe and Mn being in the range of 0.005% by mass to 7.00% by mass, and further contains 0.5% by mass to 6.5% by mass of Mg, and optionally contains one or more metals selected from the group consisting of 0% by mass to 1.0% by mass of Si (silicon), 0% by mass to 0.7% by mass of Zn (zinc), 0% by mass to 0.30% by mass of Cr (chromium), and 0% by mass to 0.20% by mass of Zr (zirconia), with the balance being Al and unavoidable impurities and other trace components.

[0045] Examples of unavoidable impurities include Ti (titanium) and Ga (gallium) contained in aluminum alloys, and other trace components include Co (cobalt) and Pt (platinum), which are components contained in plating and magnetic materials that could not be completely separated from recycled materials. The effects of the present invention are not impaired if the content of these unavoidable impurities and other trace components is 0.10% by mass or less for each element and 0.30% by mass or less in total.

[0046] 4-2. Heating and holding molten aluminum alloy Next, the molten metal heating and holding process for heating and holding the molten metal of the aluminum alloy will be described. In this process, the molten metal of the aluminum alloy is heated and held in a holding furnace under the conditions described below. At this time, it is preferable to remove the oxide film floating on the surface of the molten metal outside the furnace. By removing the floating oxide film, etc. by a method such as scooping before casting the aluminum alloy, the content of Ni and P in the molten metal can be reduced. Here, since the oxide film contains a part of the base layer that should be removed, if the oxide film is left on the surface of the molten metal for a long time, there is a possibility that the components contained in the base layer will be mixed into the molten metal again. Therefore, it is preferable to remove the oxide film outside the furnace as quickly as possible.

[0047] 4-3. Casting aluminum alloy (step S103) Next, the casting process of the aluminum alloy will be described. The heated and held molten aluminum alloy is cast into an aluminum alloy ingot by a semi-continuous casting method (DC casting method), a metal mold casting method, a continuous casting method (CC method), or the like after in-line degassing treatment or in-line filtration treatment described later as necessary (step S103). In the DC casting method, the molten metal poured through a spout is solidified by the bottom block, the water-cooled mold wall, and cooling water directly discharged to the outer periphery of the ingot, and is drawn downward as an ingot. In the metal mold casting method, the molten metal poured into a hollow mold made of cast iron or the like is solidified by the mold wall, and an ingot is produced. In the CC casting method, the molten metal is supplied through a casting nozzle between a pair of rolls (or a belt caster or a block caster), and a thin plate is directly cast by removing heat from the rolls.

[0048] The molten metal heated and held in the molten metal heating and holding process is preferably subjected to in-line degassing treatment or in-line filtration treatment according to a conventional method before being subjected to the casting process. As the in-line degassing treatment device, a degassing device commercially available under the trademarks of SNIF, ALPUR, etc. can be used. These in-line degassing treatment devices supply gas into the molten metal as fine bubbles by rotating a rotor with blades at high speed while blowing argon gas or a mixed gas of argon and nitrogen into the molten metal. This allows the dehydrogenation gas and removal of inclusions to be performed in-line in a short time. As the in-line filtration process, a ceramic tube filter, a ceramic foam filter, an alumina ball filter, etc. are used, and inclusions are removed by a cake filtration mechanism, a filter medium filtration mechanism, etc.

[0049] Through the above steps, an aluminum alloy ingot is produced.

[0050] 5. Manufacturing method of aluminum alloy plate The method for producing an aluminum alloy plate includes a homogenization step of optionally heat-treating the aluminum alloy ingot obtained by the above-mentioned production method, a hot rolling step of hot-rolling the optionally homogenized aluminum alloy ingot, and a cold rolling step of cold-rolling the hot-rolled hot-rolled plate. Specifically, the aluminum alloy plate is produced through the steps of homogenization (step S104), hot rolling (step S105), and cold rolling (step 106) of the aluminum alloy ingot as shown in Fig. 2.

[0051] 5-1. Homogenization process (step S104) The cast aluminum alloy ingot is subjected to homogenization treatment as necessary (step S104). When homogenization treatment is performed, the aluminum alloy ingot is heated at a heating temperature of preferably 480°C to 560°C for 1 hour or more, more preferably at a heating temperature of 500°C to 550°C for 2 hours or more. If 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. Furthermore, if the heating temperature exceeds 560°C, the aluminum alloy ingot may melt. Furthermore, although there is no particular upper limit on the heating time, if it exceeds 48 hours, the homogenization effect may be saturated, resulting in a decrease in productivity.

[0052] 5-2. Hot rolling (step S105) Next, the cast aluminum alloy ingot, or the homogenized aluminum alloy ingot, if homogenized, is hot-rolled to produce a hot-rolled sheet (step S105). The conditions of the hot rolling are not particularly limited, but the hot rolling start temperature is preferably 300°C or more and 500°C or less, and more preferably 320°C or more and 480°C or less. The hot rolling end temperature is preferably 260°C or more and 400°C or less, and more preferably 280°C or more and 380°C or less. 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 may become coarse and the adhesion of the plating may decrease. 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 may become coarse and the adhesion of the plating may decrease. In the hot rolling, the ingot is usually heated and held at the hot rolling starting temperature for 0.5 to 10.0 hours before the hot rolling. When homogenization treatment is performed, the heating and holding may be replaced by the homogenization treatment.

[0053] 5-3. Cold rolling (step S106) Next, the obtained hot-rolled sheet is cold-rolled to produce a cold-rolled sheet having a thickness of preferably 0.4 mm to 2.0 mm, more preferably 0.6 mm to 2.0 mm (step S106). That is, after the hot rolling is completed, the required product sheet thickness is finished by cold rolling. The conditions of the cold rolling are not particularly limited, but may be determined according to the required sheet strength and sheet thickness of the product, and the rolling reduction is preferably 20% to 90%, more preferably 20% to 80%. If the rolling reduction is less than 20%, the crystal grains may become coarse during the pressure flattening annealing of the disk blank described later, and the adhesion of the plating may decrease. On the other hand, if the rolling reduction exceeds 90%, the manufacturing time may be extended, which may lead to a decrease in productivity.

[0054] In order to ensure good cold rolling workability, annealing may be optionally performed before or during cold rolling. When annealing is performed, for example, in batch annealing, it is preferable to perform the annealing at an annealing temperature of 300°C to 450°C for 0.1 to 10 hours, and more preferably at an annealing temperature of 300°C to 380°C for 1 to 5 hours. If the annealing temperature is less than 300°C and / or the annealing time is less than 0.1 hours, sufficient annealing effect may not be obtained. In addition, if the annealing temperature exceeds 450°C, the crystal grains may become coarse and the adhesion of the plating may decrease, and if the annealing time exceeds 10 hours, the manufacturing time may be extended, which may lead to a decrease in productivity.

[0055] On the other hand, in the case of continuous annealing, it is preferable to perform the annealing at an annealing temperature of 400°C or more and 500°C or less for a holding time of 0 to 60 seconds, and more preferably perform the annealing at an annealing temperature of 450°C or more and 500°C or less for a holding time of 0 to 30 seconds. If the annealing temperature is less than 400°C, a sufficient annealing effect may not be obtained, and if the annealing temperature exceeds 500°C, the crystal grains may become coarse and the adhesion of the plating may decrease. Also, if the holding time exceeds 60 seconds, the crystal grains may become coarse and the adhesion of the plating may decrease. A holding time of 0 seconds means that the desired annealing temperature is reached and then immediately cooled.

[0056] Through the above steps, an aluminum alloy plate is produced.

[0057] 6. Manufacturing method of aluminum alloy substrate for plating The method for producing an aluminum alloy substrate for plating includes a processing step of processing the aluminum alloy plate obtained by the above-mentioned production method into an annular disk blank, a pressure annealing step of pressurizing and flattening the annular disk blank, and a cutting and grinding step of cutting and grinding the pressurized and flattened annular disk blank. Specifically, the aluminum alloy substrate for plating is produced through the steps of punching an aluminum alloy plate into an annular disk blank (hereinafter, sometimes referred to as a "disk blank") (step S107) as shown in Fig. 2, pressure flattening annealing of the disk blank (step S108), subsequent cutting and grinding (step 109: "cutting and grinding step"), and further, as necessary, a distortion relief heat treatment (step S110).

[0058] 6-1. Preparation of an annular disc blank (step S107) To process the aluminum alloy plate obtained as described above into an aluminum alloy substrate, first, the aluminum alloy plate is punched into an annular shape to produce an annular disk blank (step S107).

[0059] 6-2. Pressure annealing (step 108) Next, the disk blank is subjected to pressure annealing in air at a temperature of 300°C to 450°C for 30 minutes or more, preferably at a temperature of 300°C to 380°C for 60 minutes or more, to produce a flattened disk blank (step S108). If the pressure annealing treatment temperature is less than 300°C and / or the treatment time is less than 30 minutes, the flattening effect may not be sufficiently obtained. If the treatment temperature exceeds 450°C, the crystal grains may become coarse and the adhesion of the plating may decrease. There is no particular upper limit to the treatment time, but if it exceeds 24 hours, the manufacturing time may be extended, which may lead to a decrease in productivity. The pressure in the pressure annealing is usually 0.1 MPa to 3.0 MPa.

[0060] 6-3. Cutting and grinding (step S109), distortion removal heat treatment (step S110) Next, the disk blank flattened in the cutting and grinding process is cut and ground (step S109), and then optionally subjected to distortion relief heat treatment at a temperature of 200° C. to 290° C. for 0.1 to 10.0 hours (step S110) to remove distortion of the disk blank.

[0061] Through the above steps, an aluminum alloy substrate for plating is produced.

[0062] 7. Manufacturing method of aluminum alloy substrate for magnetic disk The manufacturing method of the aluminum alloy substrate for magnetic disk includes a plating pretreatment step of degreasing, etching and zincating the aluminum alloy substrate for plating obtained by the above manufacturing method, and a base plating step of electrolessly plating the surface of the aluminum alloy substrate for plating pretreatment with Ni-P and polishing the plated surface. As shown in Fig. 2, such an aluminum alloy substrate for magnetic disk is manufactured through the steps of plating pretreatment (step S111) of the aluminum alloy substrate for plating and base (Ni-P) plating (with polishing) (step S112).

[0063] 7-1. Plating pretreatment (step 111) The aluminum alloy substrate for plating prepared as described above is subjected to degreasing, etching, and zincate treatment (Zn substitution treatment) as pretreatment for plating (step S111). Degreasing is preferably performed using a commercially available AD-68F (Uemura Kogyo Co., Ltd.) degreasing solution or the like under conditions of a degreasing temperature of 40°C to 70°C, a degreasing time of 3 minutes to 10 minutes, and a degreasing solution concentration of 200mL / L to 800mL / L, and more preferably a degreasing temperature of 45°C to 65°C, a degreasing time of 4 minutes to 8 minutes, and a degreasing solution concentration of 300mL / L to 700mL / L. If the degreasing temperature is less than 40°C, the degreasing time is less than 3 minutes, and / or the degreasing solution concentration is less than 200mL / L, sufficient degreasing effect may not be obtained. Furthermore, 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 surface smoothness of the aluminum alloy substrate may decrease, and pits may occur after plating, resulting in a decrease in smoothness.

[0064] Etching is preferably performed using, for example, a commercially available AD-107F (Uemura Kogyo Co., Ltd.) etching solution under the conditions of an etching temperature of 50°C to 75°C, an etching time of 0.5 minutes to 5 minutes, and an etching solution concentration of 20mL / L to 100mL / L, and more preferably under the conditions of an etching temperature of 55°C to 70°C, an etching time of 0.5 minutes to 3 minutes, and an etching solution concentration of 40mL / L to 100mL / L. If the etching temperature is less than 50°C, the etching time is less than 0.5 minutes, and / or the etching solution concentration is less than 20mL / L, sufficient etching effect may not be obtained. If the etching temperature exceeds 75°C, the etching time exceeds 5 minutes, and / or the etching solution concentration exceeds 100mL / L, the smoothness of the surface of the aluminum alloy substrate may decrease, and pits may occur after the plating process, resulting in a decrease in smoothness. Note that a normal desmutting process may be performed between the etching process and the zincate process described below.

[0065] The zincate treatment is preferably carried out 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 to 35°C, a zincate treatment time of 0.1 to 5 minutes, and a zincate treatment solution concentration of 100mL / L to 500mL / L, and more preferably at a zincate treatment temperature of 15°C to 30°C, a zincate treatment time of 0.1 to 2 minutes, and a zincate treatment solution concentration of 200mL / L to 400mL / L. If the zincate treatment temperature is less than 10°C, the zincate treatment time is less than 0.1 minutes, and / or the zincate treatment solution concentration is less than 100mL / L, the zincate film may become non-uniform, pits may occur after plating, and smoothness may decrease. In addition, if 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 coating may become non-uniform, and pits may occur after plating treatment, resulting in a decrease in smoothness.

[0066] 7-2. Base (Ni-P) plating treatment (with polishing) (Step 112) Next, the surface of the zincate-treated aluminum alloy substrate for plating is subjected to electroless Ni-P plating as a base treatment, and then the surface is polished (step S112). The electroless Ni-P plating is preferably performed using, for example, a commercially available Nimden HDX (manufactured by Uemura Kogyo Co., Ltd.) plating solution under the conditions of a plating temperature of 80°C to 95°C, a plating time of 30 minutes to 180 minutes, and a Ni concentration in the plating solution of 3 g / L to 10 g / L, and more preferably under the conditions of a plating temperature of 85°C to 95°C, a plating time of 60 minutes to 120 minutes, and a Ni concentration in the plating solution of 4 g / L to 9 g / L. 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 plating growth rate is slow, which may lead to a decrease in productivity. Also, if the plating time is less than 30 minutes, many 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 10g / L, the plating may grow non-uniformly, resulting in a decrease in the smoothness of the plating. Also, if the plating time exceeds 180 minutes, the manufacturing time may become longer, which may result in a decrease in productivity. Furthermore, the surface of the base (Ni-P) plating is polished.

[0067] Through these pre-plating treatments and the undercoat (Ni-P) plating treatment (with polishing), an aluminum alloy substrate for a magnetic disk is produced.

[0068] 8. Manufacturing method of magnetic disk The method for manufacturing a magnetic disk includes a magnetic layer forming step of adhering a magnetic material to the surface of the aluminum alloy substrate for magnetic disk obtained by the above-mentioned manufacturing method. Such a magnetic disk is produced by adhering a magnetic material to the surface of the aluminum alloy substrate for magnetic disk that has been subjected to surface treatment, as shown in FIG. 2 (step S113).

[0069] After the electroless Ni-P plating process including the polishing process, a magnetic material is attached on the Ni-P plating layer by sputtering to form a magnetic layer (step S113). The magnetic layer may be a single layer, or may be formed of multiple layers having different compositions. 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.

[0070] By the above steps, a magnetic disk can be manufactured, which has a Ni-P plating layer on the surface of the aluminum alloy substrate for magnetic disk and a magnetic layer formed on the Ni-P plating layer. The magnetic disk obtained by the manufacturing method of such a magnetic disk is manufactured using the above-mentioned recycled material, and is therefore useful as a magnetic disk that is excellent in reducing environmental load.

[0071] Based on the above-mentioned embodiments, the present invention relates to the following [1] to

[14] . [1] An aluminum alloy disk material having a peeled surface formed by peeling off the underlayer from at least one of a recycled material of an intermediate material and a finished product, the intermediate material comprising an aluminum alloy disk and a Ni-containing underlayer, the aluminum alloy disk material having an oxide film on the surface of the peeled surface. [2] The aluminum alloy disk material according to the above-mentioned [1], wherein the oxide film contains at least one of S and P. [3] The aluminum alloy disk material according to the above [1] or [2], wherein the underlayer includes a Ni-P plating layer. [4] A method for producing an aluminum alloy raw material, comprising a separation step of reusing at least one of an intermediate material and a finished product comprising an aluminum alloy disk and a Ni-containing underlayer as a recycled material for at least a part of an aluminum alloy material, and separating the aluminum alloy disk and the underlayer by heating or wet treating the aluminum alloy material containing the recycled material, wherein an oxide film is formed on the peeled surface of the aluminum alloy disk material obtained by peeling off the underlayer. [5] The method for producing an aluminum alloy raw material according to the above-mentioned [4], wherein, when a quantitative elemental analysis is performed in a depth direction from the surface of the oxide film by glow discharge optical emission spectroscopy, the time required for the peak of the emission intensity of oxygen (O) to reach half of its peak is 0.1 seconds or more. [6] The method for producing an aluminum alloy raw material according to the above [4] or [5], wherein the oxide film contains at least one of S and P. [7] A method for producing an aluminum alloy ingot, comprising: a molten metal preparation step of preparing a molten aluminum alloy using at least a part of the aluminum alloy raw material obtained by the production method described in [4] to [6] above; a molten metal heating and holding step of heating and holding the prepared molten metal; and a casting step of casting the heated and held molten metal. [8] The method for producing an aluminum alloy ingot according to [7] above, wherein in the molten metal heating and holding step, oxides present on the surface of the molten aluminum alloy are removed. [9] A method for producing an aluminum alloy sheet, comprising: a homogenization treatment step of optionally heat-treating an aluminum alloy ingot obtained by the production method according to the above-mentioned [7] or [8]; a hot rolling step of hot-rolling the optionally homogenized aluminum alloy ingot; and a cold rolling step of cold-rolling the hot-rolled sheet.

[10] A method for producing an aluminum alloy substrate for plating, comprising: a processing step of processing the aluminum alloy plate obtained by the manufacturing method described in [9] above into an annular disk blank; a pressure annealing step of pressurizing and flattening the annular disk blank; and a cutting and grinding step of cutting and grinding the pressurized and flattened annular disk blank.

[11] A method for producing an aluminum alloy substrate for magnetic disks, comprising the steps of: a pre-plating step of subjecting the aluminum alloy substrate for plating obtained by the method described in

[10] above to degreasing, etching and zincating; and a base plating step of subjecting the surface of the pre-plating-treated aluminum alloy substrate to electroless Ni-P plating and polishing the plated surface.

[12] A method for producing a magnetic disk, comprising the step of adhering a magnetic material to a surface of an aluminum alloy substrate for a magnetic disk obtained by the method according to the above-mentioned

[11] to form a magnetic material layer.

[13] A magnetic disk obtained by the manufacturing method described in

[12] above.

[0072] The aluminum alloy disk material, the method for producing an aluminum alloy raw material, the method for producing an aluminum alloy ingot, the method for producing an aluminum alloy plate, the method for producing an aluminum alloy substrate for plating, the method for producing an aluminum alloy substrate for magnetic disks, the method for producing a magnetic disk, and the magnetic disk according to the present embodiments have been described above, but the present invention is not limited to the above embodiments, and various modifications and changes are possible based on the technical concept of the present invention. EXAMPLES

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0074] An aluminum alloy substrate for magnetic disks (hereinafter referred to as "aluminum alloy substrate") was used as the recycled material, which was heated and cooled or electrolyzed with sulfuric acid under the conditions shown in Table 1 to separate the underlayer and produce an aluminum alloy raw material (aluminum alloy disk material). The sulfuric acid electrolysis was carried out using sulfuric acid with a concentration of 100 g / L under conditions of a temperature of 25°C, a treatment time of 4 minutes, and an applied voltage of 2 V.

[0075] The P content in the Ni-P plating layer attached to the aluminum alloy substrate used as the recycled material was about 12 mass% with respect to the total mass of the aluminum alloy substrate. The alloy composition of the aluminum alloy used for the aluminum alloy substrate had a total content of Fe and Mn ranging from 0.015 mass% to 0.030 mass%, contained 3.8 mass% to 4.5 mass% Mg, contained 0.005 mass% or less Ni, and further contained one or more metals selected from the group consisting of Si: 0.03 mass% or less, Zn: 0.30 mass% to 0.40 mass% or less, Cr: 0.04 mass% to 0.06 mass% or less, and Cu: 0.005 mass% to 0.025 mass% or less, with the remainder being Al, unavoidable impurities, and trace components.

[0076] To evaluate the separability, the amount of Ni (Na) [mass %] of the ingot after melting and casting the aluminum alloy disk material after separation by heating or wet processing was measured, and the separation ratio (Ns = (1-Na / Nd) x 100) was calculated from the amount of Ni (Nd) [mass %] of the entire aluminum alloy disk material before separating the base layer. Note that 3.9 mass % is used as the representative value of the amount of Ni (Nd).

[0077] Whether an oxide film was formed on the peeled surface of the aluminum alloy disk material after separation by heating or wet treatment was determined by GDS. Quantitative elemental analysis by GDS was performed in the depth direction from the surface of the peeled surface. When a peak in the emission intensity of oxygen (O) was observed, it was determined that an oxide film was formed. When an oxide film was formed, for the time when the peak in the emission intensity of O became half, and for the presence or absence of P and S in the oxide film, the settings of GDS ("JY5000RF", manufactured by HORIBA) were set to a gas pressure of 400 Pa and an output of 30 W, and the emission intensities of O, P, and S were measured with a sputtering time of 15 seconds. From the measured data, the time when the peak in the emission intensity of O became half was calculated using the following calculation formula, and the presence or absence of P and S in the oxide film was determined. Examples of the results are shown in FIGS. 3A - B and FIGS. 4A - B.

[0078] <Presence or absence of peak in emission intensity of O> When (average value of emission intensity of O until sputtering time less than 1.0 second) / (average value of emission intensity of O from sputtering time 7.0 seconds or more to less than 8.0 seconds) was 1 or more, it was determined that an oxide film was formed.

[0079] <Time when peak in emission intensity of O becomes half> (Emission intensity of O at each sputtering time) - (average value of emission intensity of O for sputtering time 7 - 10 seconds) - ((maximum value of emission intensity of O) - (average value of emission intensity of O for sputtering time 7 - 10 seconds)) / 2 was calculated, and the sputtering time immediately before the value became negative was regarded as the time when the peak in the emission intensity of O became half. In addition, when the oxide film was thick and the sputtering time of 15 s was insufficient, the sputtering time was increased. In that case, (average value of emission intensity of O for sputtering time 7 - 10 seconds) was not the sputtering time of 7 - 10 seconds, but was calculated as the average value at the sputtering time multiplied by the value of (new sputtering time / 15).

[0080] <Presence or absence of P content> When (average value of emission intensity of P until sputtering time less than 0.1 second) / (average value of emission intensity of P from sputtering time 0.3 seconds or more to less than 0.5 seconds) was 2 or more, it was determined that P was contained in the oxide film.

[0081] <Presence or absence of S content> When the average value of the emission intensity of S until the sputtering time is less than 0.1 second / the average value of the emission intensity of S until the sputtering time is 0.3 second or more and less than 0.5 second is 3 or more, it was determined that P is contained in the oxide film.

[0082]

Table 1

[0083] As shown in Table 1, in Examples 1 to 5, the separation ratio was 98% or more, and excellent recyclability results were obtained. In particular, in Examples 2 to 4 where the time for the peak of the emission intensity of O to become half was long, and in Example 1 where both P and S were contained in the oxide film, the separation ratio was high and the recyclability was more excellent.

[0084] On the other hand, in Comparative Example 1, since a part of the aluminum alloy disk was melted and it was difficult to peel the underlying layer, analysis by GDS became difficult, the oxide film could not be confirmed, and the peeling ratio was less than 60%, resulting in inferior recyclability.

Industrial Applicability

[0085] According to the present invention, it is possible to provide an aluminum alloy disk material, a method for manufacturing an aluminum alloy raw material, a method for manufacturing an aluminum alloy ingot, a method for manufacturing an aluminum alloy plate, a method for manufacturing an aluminum alloy substrate for plating, a method for manufacturing an aluminum alloy substrate for a magnetic disk, a method for manufacturing a magnetic disk, and a magnetic disk, which are excellent in recyclability.

Claims

1. An aluminum alloy disk material having a peeled surface formed by peeling off the base layer from at least one of a recycled material of an intermediate material and a finished product comprising an aluminum alloy disk and a base layer containing Ni, the aluminum alloy disk material being characterized in that the peeled surface has an oxide film on its surface.

2. The aluminum alloy disk material according to claim 1 , wherein the oxide film contains at least one of S and P.

3. 3. The aluminum alloy disk material according to claim 1, wherein the underlayer includes a Ni-P plating layer.

4. A method for producing an aluminum alloy raw material, comprising a separation step of reusing at least one of an intermediate material and a finished product comprising an aluminum alloy disk and a Ni-containing underlayer as a recycled material for at least a part of an aluminum alloy material, and separating the aluminum alloy disk and the underlayer by heating or wet treating the aluminum alloy material containing the recycled material, wherein an oxide film is formed on the peeled surface of the aluminum alloy disk material obtained by peeling off the underlayer.

5. 5. The method for producing an aluminum alloy raw material according to claim 4, wherein, when a quantitative elemental analysis is performed in a depth direction from a surface of the oxide film by glow discharge optical emission spectroscopy, a time required for a peak of an emission intensity of oxygen (O) to become half is 0.1 seconds or more.

6. The method for producing an aluminum alloy raw material according to claim 4 or 5, wherein the oxide film contains at least one of S and P.

7. 6. A method for producing an aluminum alloy ingot, comprising: a molten metal preparing step of preparing a molten aluminum alloy using at least a part of the aluminum alloy raw material obtained by the production method according to claim 4 or 5; a molten metal heating and holding step of heating and holding the prepared molten metal; and a casting step of casting the heated and held molten metal.

8. The method for producing an aluminum alloy ingot according to claim 7, wherein an oxide film present on a surface of the molten aluminum alloy is removed in the molten metal heating and holding step.

9. 8. A method for producing an aluminum alloy plate, comprising: a homogenization treatment step of optionally heat-treating an aluminum alloy ingot obtained by the production method according to claim 7; a hot rolling step of hot-rolling the optionally homogenized aluminum alloy ingot; and a cold rolling step of cold-rolling the hot-rolled hot-rolled plate.

10. 10. A method for producing an aluminum alloy substrate for plating, comprising: a processing step of processing the aluminum alloy plate obtained by the manufacturing method according to claim 9 into an annular disk blank; a pressure annealing step of pressurizing and flattening the annular disk blank; and a cutting and grinding step of cutting and grinding the pressurized and flattened annular disk blank.

11. A method for producing an aluminum alloy substrate for magnetic disks, comprising the steps of: a pre-plating step of subjecting the aluminum alloy substrate for plating obtained by the method for producing according to claim 10 to degreasing, etching and zincating; and a base plating step of subjecting the surface of the aluminum alloy substrate for plating pre-treated to electroless Ni-P plating and polishing the plated surface.

12. A method for producing a magnetic disk, comprising the step of adhering a magnetic material to the surface of an aluminum alloy substrate for a magnetic disk obtained by the method according to claim 11 to form a magnetic material layer.

13. A magnetic disk obtained by the manufacturing method according to claim 12.

Images