JP2023032363A - Method for producing aluminum alloy ingot for magnetic disk, method for producing aluminum alloy plate for magnetic disk using the aluminum alloy ingot, method for producing aluminum alloy substrate for magnetic disk using the aluminum alloy plate, and magnetic disk using the aluminum alloy substrate - Google Patents

Abstract

A method for producing an aluminum alloy ingot for a magnetic disk excellent in recyclability, a method for producing an aluminum alloy plate for a magnetic disk using the same, a method for producing an aluminum alloy substrate for a magnetic disk using the same, and a method for producing the aluminum alloy substrate for the magnetic disk using the same Provided is a magnetic disk using an aluminum alloy substrate manufactured by
A method for producing an aluminum alloy ingot for a magnetic disk uses at least one of an intermediate material and a finished product obtained in the production of the magnetic disk as a recycled material as at least a part of the raw material, and aluminum made of the raw material It includes a molten metal adjustment step of adjusting the molten alloy, a molten metal heating and holding step of heating and holding the adjusted molten metal, and a casting step of casting the heated and held molten metal. In the molten metal heating and holding step, the molten metal is heated and held at 700 to 850° C. for 3 hours or more.
[Selection drawing] Fig. 1

Description

The present invention provides a method for producing an aluminum alloy ingot for a magnetic disk excellent in recyclability, a method for producing an aluminum alloy plate for a magnetic disk using this ingot, and an aluminum alloy substrate for a magnetic disk using this aluminum alloy plate. The present invention relates to a manufacturing method and a magnetic disk using this aluminum alloy substrate.

Aluminum alloy magnetic disks used in computer memory devices have good plating properties and excellent mechanical properties and workability according to JIS 5086 (3.5 mass% or more and 4.5 mass% or less 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 The following Cu, Ti less than 0.15% by mass, Zn less than 0.25% by mass, balance Al and unavoidable impurities) as a base.

Furthermore, in aluminum alloy magnetic disks, the content of impurities such as Fe, Si, and Mn in JIS 5086 is limited for the purpose of improving pit defects caused by falling off of intermetallic compounds in the pretreatment process for plating. It is manufactured from an aluminum alloy substrate with reduced intercalation compounds, an aluminum alloy substrate to which Cu or Zn in JIS5086 is intentionally added for the purpose of improving plating properties, or the like.

A general aluminum alloy magnetic disk is produced by first producing an aluminum alloy plate, then producing an annular aluminum alloy disk blank, performing cutting and grinding, and then subjecting it to pressure annealing to form an aluminum alloy substrate. . Then, the aluminum alloy substrate is plated, and a magnetic material is adhered to the surface of the aluminum alloy substrate.

For example, an aluminum alloy magnetic disk using the JIS5086 alloy is manufactured by the following manufacturing process. First, an aluminum alloy having a desired chemical 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. The rolled material is annealed during the cold rolling, if necessary. Next, this rolled material is punched into an annular shape, and an annular aluminum alloy plate is laminated to remove the distortion caused by the manufacturing process, and pressure annealing is performed to flatten it by annealing while applying pressure from both sides. A disc blank is produced by performing.

After cutting and grinding the disk blank thus produced as a pretreatment, the disk blank is heat-treated to remove distortions and the like caused by the machining process, thereby producing an aluminum alloy substrate. be done. Next, degreasing, etching, and zincate treatment (Zn replacement treatment) are performed as pre-plating treatments, and Ni-P plating, which is a hard non-magnetic metal, is applied as a base treatment, and the surface is polished to remove the aluminum alloy substrate. produced. Finally, a magnetic disk is manufactured by sputtering a magnetic material or the like.

By the way, in recent years, magnetic disks are required to have a large capacity and a high density due to the needs of multimedia and the like. The number of magnetic disks mounted in a storage device is increasing in order to further increase the capacity, and along with this, there is also a demand for thinner magnetic disks. However, if the thickness of the aluminum alloy substrate for a magnetic disk is reduced, the rigidity of the substrate decreases. Therefore, the aluminum alloy substrate is required to have a high rigidity. .

On the other hand, as the number of mounted magnetic disks increases, the required amounts of Al, Ni, etc., which are raw materials for aluminum alloy substrates for magnetic disks, are increasing. However, since these resources are limited, it is required to reuse not only aluminum alloy substrates but also aluminum alloy substrates and magnetic disks to which plating and magnetic substances are adhered as raw materials for aluminum alloy substrates. In the case of aluminum alloy substrates, defective products that are not suitable as products are used, and in the case of magnetic disks, defective products or those extracted from used HDDs are used.

Under such circumstances, in recent years, there have been proposed a method for producing an aluminum alloy ingot for a magnetic disk excellent in recyclability, a method for producing an aluminum alloy plate for a magnetic disk using this ingot, and a method for producing a magnetic disk using this aluminum alloy plate. A method for manufacturing an aluminum alloy substrate and a magnetic disk using this aluminum alloy substrate are strongly desired and are being investigated. For example, Patent Literature 1 proposes that an aluminum alloy substrate can be reused as a raw material by including Ni in an aluminum alloy for a magnetic disk.

Japanese Patent Application Laid-Open No. 2002-275568

However, in the method disclosed in Patent Document 1, when an aluminum alloy substrate is produced using an aluminum alloy substrate as a raw material, the P content cannot be sufficiently reduced, plating defects occur, and the plating surface There is a problem that the smoothness of the surface is deteriorated.

The present invention has been made in view of the above circumstances, and provides a method for producing an aluminum alloy ingot for a magnetic disk excellent in recyclability, a method for producing an aluminum alloy plate for a magnetic disk using this aluminum alloy ingot, and a method for producing an aluminum alloy plate for a magnetic disk using this aluminum alloy ingot. An object of the present invention is to provide a method for manufacturing an aluminum alloy substrate for a magnetic disk using an aluminum alloy plate, and a magnetic disk using this aluminum alloy substrate.

The present inventors controlled the heating temperature and holding time in the heating and holding process of the molten metal for casting, and furthermore, by adjusting the Cu content in the molten metal, an aluminum alloy ingot for a magnetic disk excellent in recyclability was produced. The present inventors have found that it can be obtained, and have completed the present invention.

That is, the present invention provides a method for producing an aluminum alloy ingot for a magnetic disk according to claim 1, wherein at least one of the intermediate material and the finished product obtained in the production of the magnetic disk is used as at least a part of the raw material as a recycled material. A molten metal adjustment step of adjusting the molten metal of the aluminum alloy made of the raw material, a molten metal heating and holding step of heating and holding the adjusted molten metal, and a casting step of casting the heated and held molten metal, and the molten metal heating and holding step 3, the method for producing an aluminum alloy ingot for a magnetic disk is characterized in that the molten metal is heated and held at 700 to 850° C. for 3 hours or more.

In claim 2 of the present invention, in claim 1, the Cu content of the aluminum alloy in the molten metal is 1.0 mass% or less in the step of heating and holding the molten metal.

In claim 3, the present invention provides a homogenization treatment step of heat-treating the ingot produced by the method according to claim 1 or 2, a hot-rolling step of hot-rolling the homogenized ingot, and a cold-rolling step of cold-rolling a cold-rolled hot-rolled plate.

In claim 4, the present invention provides a processing step of processing the aluminum alloy plate for a magnetic disk manufactured by the method of claim 3 into an annular disk blank, and a pressure annealing step of pressurizing and flattening the annular disk blank. and a cutting/grinding step of cutting and grinding the pressure-flattened annular disk blank.

According to claim 5 of the present invention, an electroless Ni—P plating layer and a and a magnetic layer.

A method for producing an aluminum alloy ingot for a magnetic disk according to the present invention, a method for producing an aluminum alloy plate for a magnetic disk using this aluminum alloy ingot, a method for producing an aluminum alloy substrate for a magnetic disk using this aluminum alloy plate, In addition, a magnetic disk using this aluminum alloy substrate has a special effect of being excellent in recyclability.

A method for producing an aluminum alloy ingot for a magnetic disk according to the present invention, a method for producing an aluminum alloy plate for a magnetic disk using this aluminum alloy ingot, a method for producing an aluminum alloy substrate for a magnetic disk using this aluminum alloy plate, It is also a flow chart showing a manufacturing process of a magnetic disk using this aluminum alloy substrate.

In using at least one of the intermediate material and the finished product obtained in the manufacture of the magnetic disk as a recycled material as at least a part of the raw material, the present inventors have found that the pre-casting process of the molten aluminum alloy made of the raw material We investigated the recyclability in relation to the process of heating and holding the molten metal. Specifically, intensive research was conducted on the relationship between the heating temperature, the holding time, the amount of specific components in the molten metal, and the P content in the aluminum ingot produced from the molten metal in the molten metal heating and holding step.

Here, the recycled material used in the present invention is a material in which a Ni—P plating layer exists. It is sometimes described as an "alloy base"), and the finished product is, needless to say, the magnetic disk shown in FIG. These recycled materials include defective products, non-standard products, used magnetic disks, and the like.

The reason for focusing on the P content in the aluminum ingot is as follows. P is contained as an electroless Ni—P plating component in aluminum alloy substrates and magnetic disks used as recycled materials. This P component produces a Cu—P-based compound with Cu, which is usually contained in an aluminum alloy, and also produces an Mg—P-based oxide with Mg, which is usually contained in an aluminum alloy. This is because these become large defects (such as pits) that occur on the plating surface and reduce the smoothness of the plating surface.

The present inventors have found that the holding temperature and holding time of the molten metal, as well as the Cu content and Mg content in the molten metal, have a great effect on the P content in the aluminum ingot. The present invention has been made as a result of these efforts.

1. Recycled material First, it is used as at least a part of raw materials for an aluminum alloy ingot for a magnetic disk according to an embodiment of the present invention (hereinafter sometimes referred to as "aluminum alloy ingot" or simply "alloy ingot"). , an aluminum alloy substrate and a magnetic disk, which are recycled materials, are described. "At least" means that all of the raw materials may be these recycled materials, or part of the raw materials may be these recycled materials.

1-1. Aluminum alloy base:
Since the aluminum alloy substrate has the Ni—P plating formed on the surface, it can be used as a recycled material added to at least a part of the raw material of the aluminum alloy ingot containing Ni. On the other hand, P forms Mg-P-based oxides, etc., together with Mg, which is generally contained in aluminum alloy ingots, and the reaction becomes non-uniform only in those areas during plating, causing large defects (pits, etc.) on the plating surface. Let As a result, the smoothness of the plating surface is reduced. Therefore, when using an aluminum alloy substrate as a raw material, it is important to finally reduce the P content of the aluminum alloy ingot. Incidentally, the P content of the Ni—P plating used for aluminum alloy substrates is about 8 to 15 mass %. The plating thickness is about 5 to 25 μm, and the thickness of the aluminum alloy substrate is about 0.3 to 2.0 μm.

1-2. Magnetic disk:
A magnetic disk has a CoCrPt-based magnetic material and a protective film of C or the like formed on the surface of an aluminum alloy substrate. can be removed for the most part. In addition, Ni, which is a plating component formed inside the magnetic disk, and Al, which is an aluminum alloy, can be used as raw materials for the aluminum alloy ingot. The metal contained in the magnetic material remains as it is in the aluminum alloy ingot, but its proportion is very small with respect to the entire magnetic disk. It does not impair disk performance. Also, in the case of using the magnetic disk as a raw material for the aluminum alloy ingot as well as the aluminum alloy substrate, it is important to finally reduce the P content of the aluminum alloy ingot.

Next, a method for producing an aluminum alloy ingot according to an embodiment of the present invention, a method for producing an aluminum alloy plate using this aluminum alloy ingot, a method for producing an aluminum alloy substrate using this aluminum alloy plate, and this A magnetic disk using an aluminum alloy substrate will be described in detail.

1. Manufacturing method of aluminum alloy ingot for magnetic disk As shown in FIG. Manufactured through processes.

1-1. Adjustment of Aluminum Alloy Components (Step S101)
In step S101, an aluminum alloy substrate or a magnetic disk is used as at least a part of the raw material as a recycled material, and a molten aluminum alloy having a predetermined chemical composition is prepared by heating and melting according to a conventional method (step S101 ). Regarding the component composition in the molten metal, it is preferable to define the content of Cu and Mg, which form oxides and compounds with P to form large defects on the plated surface, and the content of P itself.

Cu content: 1.0 mass% or less The Cu content in the molten aluminum alloy is preferably 1.0 mass% (hereinafter simply referred to as "%") or less. Cu combines with P, which is a plating component contained in the recycled material, to form a Cu—P-based compound, which causes large defects on the plating surface. Even if the molten metal is heated and held for a long period of time, this compound does not float on the surface of the molten metal and does not change into a removable oxide or the like. The Cu content in the molten metal is preferably 1.0% or less, more preferably 0.5% or less, still more preferably 0.1% or less. The adjustment of the Cu content is carried out in the step of adjusting the aluminum alloy components in which the raw material is heated and melted in step S101. For example, after the raw materials in the molten metal are completely melted, the components of the molten metal are analyzed, and if the Cu content is high, aluminum metal or the like is added to adjust the content to a desired value.

P content: 0.0040% or less The P content in the molten aluminum alloy is preferably 0.0040% or less. P is contained as a plating component contained in the recycled material or contained in the aluminum alloy base metal, but combines with Mg generally contained in the aluminum alloy of the raw material of the molten metal to form an Mg—P-based oxide. The reaction becomes non-uniform only in that part during the plating process, causing large defects on the plating surface. As a result, the smoothness of the plating surface is reduced. Although part of the Mg—P-based oxide can be removed by heating the molten metal to float on the surface of the molten metal, it is preferable that the content of P itself, which combines with Mg, is low. The P content in the molten metal is preferably 0.0040% or less, more preferably 0.0010% or less. Since the content of P in the molten metal is much smaller than the content of Cu, it is generally not necessary to add aluminum metal or the like to adjust the content to a desired level. However, if adjustment is required, aluminum base metal or the like is added in the same manner as Cu to adjust the content to a desired value.

Mg content: 6.5% or less:
The Mg content in the molten aluminum alloy is preferably 6.5% or less. As described above, Mg combines with P in the molten metal to form Mg—P oxides, so it is preferable that the content of Mg is as low as P. The Mg content in the molten metal is preferably 5.5% or less, more preferably 4.5% or less. When the Mg content is high, an aluminum base metal or the like is added in the same manner as Cu to adjust the content to a desired value.

Chemical composition of molten aluminum alloy:
Regarding the chemical composition of the molten aluminum alloy used in the present invention, in order to effectively remove or reduce the P component derived from the electroless Ni—P plating component contained in the recycled aluminum alloy substrate and magnetic disk, it is as described above. In addition, it is preferable to adjust the content of P itself and elements such as Cu and Mg that form compounds with P.

On the other hand, elements other than P, Cu and Mg and their contents are not particularly limited. Examples of the alloy composition of the molten aluminum alloy used in the present invention include the following. It contains Ni, which is an essential element, and one or two of Mn and Fe, which are optional elements, and the total content of these Ni, Mn and Fe has a relationship of 0.01 to 7.00%. , Mg: 0.5 to 6.5%, and further Si: 1.0% or less, Zn: 0.7% or less, Cr: 0.30% or less, and Zr: 0.20% or less It further contains one or more selected from the group, and the balance consists of Al, unavoidable impurities, and other minor components. The unavoidable impurities are those contained in the aluminum alloy, such as Ti and Ga, and other minor components include Co, Pt, etc., which are components of plating and magnetic substances. If the content of these inevitable impurities and other trace components is 0.10% or less for each element and 0.30% or less in total, the effect of the present invention is not impaired.

1-2. Molten aluminum alloy heating and holding (step S102)
Next, the molten metal heating and holding step for heating and holding the molten aluminum alloy will be described. In this step, the molten aluminum alloy is heated and held in a holding furnace under the conditions described later to adjust the P content (step S102).

The recycled materials contained in the molten aluminum alloy are the aluminum alloy substrate and the magnetic disk, and contain P as an electroless Ni—P plating component. Therefore, in order to reduce the content of P contained in the adjusted molten aluminum alloy, the molten aluminum alloy is heated and held at a holding temperature of 700 to 850° C. for 3 hours or more in the molten metal heating and holding step.

Part of the P contained in the molten metal as a raw material changes into oxides such as Mg—P-based oxides in the step of heating and holding the molten metal, and rises to the surface of the molten metal. The P content in the molten metal can be reduced by removing the floating oxide and the like by a method such as scooping up before casting. The heating temperature is 700 to 850 ° C., preferably 700 to 755 ° C. from the viewpoint of energy saving of power consumption, and the holding time is 3 hours or more, preferably 20 hours or more, thereby promoting the formation of the above oxides. can do. The retention time is important from the viewpoint of the effect of promoting the formation of the above oxides and the like. If the heating temperature is less than 700° C. or the holding time is less than 3 hours, a sufficient effect of promoting the formation of the above oxides and the like cannot be obtained. If the heating temperature exceeds 850° C., the effect of promoting the formation of oxides and the like is saturated, which is not economical. Although the upper limit of the holding time is not particularly set, even if it exceeds 72 hours, the effect of promoting the formation of the above-mentioned oxides etc. is saturated and it is not economical.

1-3. Casting of aluminum alloy (step S103)
Next, an aluminum alloy casting process will be described.
The heated and held aluminum alloy molten metal is subjected to semi-continuous casting method (DC casting method), die casting method, continuous casting method (CC method) after in-line degassing treatment and in-line filtration treatment as described later, if necessary. etc. (step S103). In the DC casting method, the molten metal poured through the spout is cooled by cooling water discharged directly to the bottom block, the water-cooled wall of the mold, and the outer periphery of the ingot (ingot). and pulled downward as an ingot. In the mold casting method, molten metal poured into a hollow mold made of cast iron or the like loses heat to the walls of the mold and solidifies to form an ingot. In the CC casting method, a molten metal is supplied through a casting nozzle between a pair of rolls (or a belt caster or a block caster), and heat is removed from the rolls to directly cast a thin plate.

The molten metal heated and held in the molten metal heating and holding step is preferably subjected to an in-line degassing treatment and an in-line filtering treatment according to a conventional method before being applied to the casting step. As in-line degassing equipment, those commercially available under trademarks such as SNIF and ALPUR can be used. In these in-line degassing devices, while blowing argon gas or a mixed gas of argon and nitrogen into the molten metal, a rotator with blades is rotated at high speed to supply the gas as fine bubbles into the molten metal. As a result, dehydrogenation gas and inclusions can be removed in-line in a short period of time. A ceramic tube filter, a ceramic foam filter, an alumina ball filter, or the like is used for in-line filtration, and inclusions are removed by a cake filtration mechanism or a filter medium filtration mechanism.

An aluminum alloy ingot for a magnetic disk is manufactured by the above steps.

2. Manufacturing method of aluminum alloy plate for magnetic disk As shown in FIG. , cold rolling (step 106).

2-1. Homogenization process (step S104)
The cast aluminum alloy ingot is optionally subjected to homogenization treatment (step S104). When the homogenization treatment is performed, the heat treatment is preferably carried out at 480 to 560° C. for 1 hour or longer, more preferably at 500 to 550° C. for 2 hours or longer. When the treatment temperature is less than 480° C. or the treatment time is less than 1 hour, a sufficient homogenization effect may not be obtained. Also, processing temperatures above 560° C. may melt the material. Moreover, although the upper limit of the treatment time is not particularly set, even if it exceeds 48 hours, the homogenization effect is saturated and the productivity is lowered.

2-2. Hot rolling (step S105)
Next, the cast aluminum alloy ingot, or the homogenized aluminum alloy ingot if homogenized, is hot-rolled into a hot-rolled plate (step S105). The hot rolling conditions are not particularly limited, but the hot rolling start temperature is preferably 300 to 500°C, more preferably 320 to 480°C. The hot rolling finish temperature is preferably 260 to 400°C, more preferably 280 to 380°C. If the hot rolling start temperature is less than 300°C, the hot rolling workability cannot be ensured, and if it exceeds 500°C, the crystal grains become coarse and the adhesion of the plating may deteriorate. If the hot-rolling finish temperature is less than 260°C, the hot-rolling workability cannot be ensured, and if it exceeds 400°C, crystal grains may become coarse and the adhesion of the plating may deteriorate. In the hot rolling, the ingot is usually heated and held at the hot rolling start temperature for 0.5 to 10.0 hours, and then hot rolled. When the homogenization treatment is performed, this heating and holding may be replaced by the homogenization treatment.

2-3. Cold rolling (step S106)
Next, the hot-rolled sheet is cold-rolled into a cold-rolled sheet of preferably 0.4-2.0 mm, more preferably 0.6-2.0 mm (step S106). That is, after completion of hot rolling, cold rolling is performed to finish the required product plate thickness. The cold rolling conditions are not particularly limited, and may be determined according to the required product plate strength and plate thickness. is more preferred. If the rolling reduction is less than 20%, crystal grains may become coarse during the pressure flattening annealing of the disk blank, and the adhesion of the plating may deteriorate. If this rolling reduction exceeds 90%, the production time will be prolonged, which may lead to a decrease in productivity.

Annealing treatment may be performed before cold rolling or during cold rolling in order to ensure good cold rolling workability. When the annealing treatment is performed, for example, in batch annealing, it is preferably performed at 300 to 450° C. for 0.1 to 10 hours, and preferably at 300 to 380° C. for 1 to 5 hours. more preferred. If the annealing temperature is less than 300° C. or the annealing time is less than 0.1 hour, a sufficient annealing effect may not be obtained. Moreover, when the annealing temperature exceeds 450° C., the crystal grains become coarse and the adhesion of the plating decreases, and when the annealing time exceeds 10 hours, the productivity may decrease.

On the other hand, continuous annealing is preferably carried out under the conditions of 400 to 500° C. and held for 0 to 60 seconds, more preferably 450 to 500° C. and held for 0 to 30 seconds. If the annealing temperature is less than 400°C, a sufficient annealing effect may not be obtained. Moreover, when the annealing temperature exceeds 500° C., the crystal grains become coarse, and the adhesion of the plating may deteriorate. If the annealing time exceeds 60 seconds, the crystal grains may become coarse and the adhesion of the plating may deteriorate. The holding time of 0 seconds means cooling immediately after reaching the desired annealing temperature.

An aluminum alloy plate for a magnetic disk is manufactured by the above steps.

3. Method for Manufacturing Aluminum Alloy Substrate for Magnetic Disk As shown in FIG. ), pressurized annealing of this disk blank (step S108), subsequent cutting and grinding (step 109, hereinafter sometimes referred to as "cutting/grinding process"), and heating for strain relief as necessary. It is manufactured through each process of processing (step S110).

3-1. Machining of annular disk 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).

3-2. Pressure annealing (step 108)
Next, the disk blank is subjected to pressure annealing at 300 to 450° C. for 30 minutes or more, preferably at 300 to 380° C. for 60 minutes or more in the atmosphere to produce a flattened disk blank (step S108). When the processing temperature of the pressure annealing is less than 300° C. or the processing time is less than 30 minutes, a sufficient flattening effect may not be obtained. If the treatment temperature exceeds 450° C., the crystal grains may become coarse and the adhesion of the plating may deteriorate. Although the upper limit of the treatment time is not particularly set, if it exceeds 24 hours, the production time becomes long, which may lead to a decrease in productivity. Incidentally, the pressurization pressure is usually 1.0 to 3.0 MPa.

3-3. Cutting/grinding (step 109), strain relief heat treatment (step 1109)
The flattened disk blank is then subjected to a cutting and grinding process (step S109). After that, a strain relief heat treatment for strain relief of the disk blank is performed at a temperature of 200 to 290° C. for 0.1 to 10.0 hours, if necessary.

An aluminum alloy substrate for a magnetic disk is manufactured by the above steps.

4. Method for Manufacturing Aluminum Alloy Substrate for Magnetic Disk As shown in FIG. It is manufactured through each process.

4-1. Plating pretreatment (step 111)
The aluminum alloy substrate produced as described above is subjected to degreasing, etching, and zincate treatment (Zn substitution treatment) as pre-plating treatment (step S111).
Degreasing is preferably performed using a commercially available AD-68F (manufactured by Uemura Kogyo) degreasing solution or the like under conditions of a temperature of 40 to 70 ° C., a treatment time of 3 to 10 minutes, and a concentration of 200 to 800 mL / L, and a temperature of 45 to 65 ° C. , a treatment time of 4 to 8 minutes, and a concentration of 300 to 700 mL/L. When the temperature is less than 40° C., when the treatment time is less than 3 minutes, or when the concentration is less than 200 mL/L, a sufficient degreasing effect may not be obtained. In addition, when the temperature exceeds 70° C., when the treatment time exceeds 10 minutes, or when the concentration exceeds 800 mL/L, the smoothness of the substrate surface decreases, pits occur after plating, and the smoothness deteriorates. may decrease.

Etching is preferably performed using a commercially available AD-107F (manufactured by Uemura Kogyo) etchant or the like under the conditions of a temperature of 50 to 75 ° C., a processing time of 0.5 to 5 minutes, and a concentration of 20 to 100 mL / L. More preferably, the conditions are 55 to 70° C., treatment time of 0.5 to 3 minutes, and concentration of 40 to 100 mL/L. If the temperature is less than 50° C., the processing time is less than 0.5 minutes, or the concentration is less than 20 mL/L, a sufficient etching effect may not be obtained. In addition, when the temperature exceeds 75° C., when the treatment time exceeds 5 minutes, or when the concentration exceeds 100 mL/L, the smoothness of the substrate surface decreases, pits occur after plating, and the smoothness is reduced. may decrease. A normal desmutting treatment may be performed between the etching treatment and the zincate treatment, which will be described later.

The zincate treatment can be performed using a commercially available zincate treatment solution such as AD-301F-3X (manufactured by Uyemura & Co., Ltd.) under conditions of a temperature of 10 to 35°C, a treatment time of 0.1 to 5 minutes, and a concentration of 100 to 500 mL/L. More preferably, the temperature is 15 to 30° C., the treatment time is 0.1 to 2 minutes, and the concentration is 200 to 400 mL/L. When the temperature is less than 10°C, when the treatment time is less than 0.1 minute, or when the concentration is less than 100 mL/L, the zincate film becomes non-uniform, pits occur after plating, and smoothness decreases. sometimes. Also, when the temperature exceeds 35°C, when the treatment time exceeds 5 minutes, or when the concentration exceeds 500 mL/L, the zincate film becomes uneven, pits occur after plating, and the smoothness decreases. Sometimes.

4-2. Base (Ni-P) plating treatment (with polishing) (step 112)
Next, the surface of the zincate-treated aluminum alloy substrate is subjected to electroless Ni—P plating as a base treatment, and then the surface is polished (step S112). Electroless Ni-P plating is carried out using a commercially available Nimden HDX (manufactured by Uemura & Co., Ltd.) plating solution or the like under conditions of a temperature of 80 to 95°C, a treatment time of 30 to 180 minutes, and a Ni concentration of 3 to 10 g/L. More preferably, the temperature is 85 to 95° C., the treatment time is 60 to 120 minutes, and the Ni concentration is 4 to 9 g/L. When the temperature is less than 80° C. or when the Ni concentration is less than 3 g/L, the plating growth rate is slow, which may lead to a decrease in productivity. If the treatment time is less than 30 minutes, many defects may occur on the plated surface and the smoothness of the plated surface may deteriorate. When the temperature exceeds 95° C. or the Ni concentration exceeds 10 g/L, the plating grows unevenly, which may reduce the smoothness of the plating. If the treatment time exceeds 180 minutes, productivity may be lowered. Further, the underlayer (Ni—P) plated surface is polished.

By these pre-plating treatments and base (Ni—P) plating treatment (with polishing), the base-treated aluminum alloy substrate for a magnetic disk of the present invention is obtained.

5. Method for Manufacturing Magnetic Disk As shown in FIG. 1, a magnetic disk is manufactured by attaching a magnetic material to the surface of an aluminum alloy substrate for a magnetic disk that has been undercoated (step S113). The manufacturing process of the magnetic disk according to the present invention will be described below.

After electroless Ni--P plating (including polishing), a magnetic layer is formed by depositing a magnetic material on the Ni--P plating layer by sputtering (step S113). The magnetic layer may be composed of a single layer, or may be composed of a plurality of layers having compositions different from each other. After sputtering, a protective layer made of a carbon-based material is formed on the magnetic layer by CVD. Next, lubricating oil is applied onto the protective layer to form a lubricating layer.

A magnetic disk can be obtained by the above steps.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.

A total of about 3 kg of the aluminum alloy substrate and the magnetic disk as recycled materials was used as the raw material (whole) of the aluminum alloy ingot. This raw material was heated and melted at 750° C. to produce a molten metal for an aluminum alloy ingot. A molten aluminum alloy was melted. Next, the molten metal was heated and held at a temperature of 750° C. for the time shown in Table 1.

The P content in the plating layer adhering to the magnetic disk aluminum alloy substrate and magnetic disk used as raw materials was about 12% with respect to the total weight of the aluminum alloy substrate or magnetic disk. In addition, the composition of the aluminum alloy used for the aluminum alloy substrate and the aluminum alloy substrate of the magnetic disk has a relationship that the total content of Ni, Mn and Fe is 0.01 to 7.00%, and Mg: 0 1 selected from the group consisting of Si: 1.0% or less, Zn: 0.7% or less, Cr: 0.30% or less and Cu: 1.0% or less It further contained seeds or two or more, and the balance consisted of Al, unavoidable impurities and trace components. For the P content shown in Table 1, each molten metal sample was subjected to normal casting by a mold casting method after each holding time, and the content in the ingot was analyzed using ICP (inductively coupled plasma) emission spectrometry. This is the measured value. A plurality (three types) of aluminum alloys having different compositions were used for the aluminum alloy substrate.

As shown in Table 1, in Examples 1 to 3, the P content was 0.0040% or less, and excellent recyclability was obtained. The longer the holding time, the lower the P content. This is because the longer the holding time, the more Mg—P oxides are produced, and the molten metal is used to remove the floated oxides. On the other hand, in Comparative Examples 1 and 2, since the holding time was insufficient, the P content exceeded 0.0040%, resulting in poor recyclability. In Comparative Example 1, the heating and holding time of the molten metal of 0 (h) means that the heating and holding time was not used at all.

According to the present invention, there are provided a method for producing an aluminum alloy ingot for a magnetic disk excellent in recyclability, a method for producing an aluminum alloy plate for a magnetic disk using this ingot, and an aluminum alloy substrate for a magnetic disk using this aluminum alloy plate. A manufacturing method and a magnetic disk using this aluminum alloy substrate can be provided.

Claims (5)

A method for producing an aluminum alloy ingot for a magnetic disk, wherein at least one of an intermediate material and a finished product obtained in the production of a magnetic disk is used as at least a part of a raw material as a recycled material, and an aluminum alloy made of the raw material is produced. It includes a molten metal adjustment step of adjusting the molten metal, a molten metal heating and holding step of heating and holding the adjusted molten metal, and a casting step of casting the heated and held molten metal. A method for producing an aluminum alloy ingot for a magnetic disk, comprising heating and holding for at least one hour. 2. The method for producing an aluminum alloy ingot for a magnetic disk according to claim 1, wherein the aluminum alloy in the molten metal has a Cu content of 1.0 mass % or less in the step of heating and holding the molten metal. A homogenization treatment step of heat-treating the ingot produced by the method according to claim 1 or 2, a hot-rolling step of hot-rolling the homogenized ingot, and a hot-rolled hot-rolled plate A method for manufacturing an aluminum alloy plate for a magnetic disk, comprising a cold rolling step of cold rolling. A processing step of processing an aluminum alloy plate for a magnetic disk manufactured by the method according to claim 3 into an annular disk blank, a pressure annealing step of pressure flattening the annular disk blank, and a pressure flattened circle A method of manufacturing an aluminum alloy substrate for a magnetic disk, comprising a cutting and grinding step of applying cutting and grinding to an annular disk blank. Having an electroless Ni—P plating layer and a magnetic layer on the electroless Ni—P plating layer on the surface of the magnetic disk aluminum alloy substrate manufactured by the method according to claim 4. A magnetic disk characterized by:

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