Aluminum alloy blank for magnetic disk and aluminum alloy substrate for magnetic disk

Abstract

Provided are an aluminum alloy blank for a magnetic disk having a high damping ratio and an aluminum alloy substrate for a magnetic disk. In the aluminum alloy blank for a magnetic disk and the aluminum alloy substrate for a magnetic disk of the present invention, Mn is 1.00 mass% or more and 10 mass% or less, the balance consists of Al and inevitable impurities, and the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 µm on the surface is 1.5 x 10 5 mm 2 or less.

Description

[0001] This application is a divisional application of PCT / JP2020 / 005290, application number 202080019720.6, application date: February 12, 2020, invention title: “Aluminum alloy blank for disk and aluminum alloy substrate for disk”. Technical Field

[0002] This invention relates to aluminum alloy blanks for hard disks and aluminum alloy substrates for hard disks. Background Technology

[0003] With the digitization of information and the widespread use of the Internet, massive amounts of digital data are being processed, requiring data centers to increase the capacity of hard disk drives (HDDs). Therefore, to achieve this increased capacity, the number of disks in each HDD unit is being increased, leading to research into thinner disk designs.

[0004] Furthermore, research on thinner disks has proposed reducing the thickness of the disks mounted on 3.5-inch HDDs from approximately 1.3mm to 0.8mm or less.

[0005] However, when a disk is in a rotating drive, especially when maintaining a stable speed at high speeds (e.g., above 7200 rpm), the thinner the disk, the higher the probability of micro-vibrations occurring.

[0006] Regarding this type of disk material, the following technology has been proposed.

[0007] For example, Patent Document 1 discloses an aluminum alloy substrate for disks, characterized in that it is composed of an aluminum alloy containing Fe: 0.4 to 3.0 mass%, with the balance being Al and unavoidable impurities, and in the metal structure, the perimeter of the second-phase particles with the longest diameter of 3 μm or more is 10 mm / mm. 2 above.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 6437583 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In order to suppress vibrations that occur with the thinning of disk walls, the inventors have conducted intensive research on disk materials with excellent properties that can attenuate this vibration; in other words, they have conducted intensive research on disk materials with high damping ratios.

[0013] Here, according to the aforementioned Patent Document 1, it is explained that by adding Fe in a specified amount, the disk jitter characteristics of the aluminum alloy substrate for disks are excellent.

[0014] However, the inventors have confirmed that adding Fe does not sufficiently improve the damping ratio. Furthermore, as a technique for suppressing disk vibration, a new technique that differs in characteristics from the technique described in Patent Document 1 is needed.

[0015] Therefore, the objective of this invention is to provide an aluminum alloy blank for a hard disk with a high damping ratio and an aluminum alloy substrate for a hard disk.

[0016] Problem-solving methods

[0017] The aluminum alloy blank and aluminum alloy substrate for disks of the present invention contain...

[0018] Mn: ≥1.00% by mass and ≤10% by mass

[0019] Fe: ≥0.005% by mass and ≤0.30% by mass

[0020] Mg: ≥0.005% by mass and ≤1.5% by mass

[0021] Cr: ≥0.005% by mass and ≤0.25% by mass

[0022] Zn: ≥0.005% by mass and ≤0.2% by mass

[0023] Cu: ≥0.005% by mass and ≤0.10% by mass

[0024] The balance includes Al and unavoidable impurities; the number density of intermetallic compounds with a maximum length of 0.2–15.0 μm in the surface is 1.5 × 10⁻⁶. 5 pcs / mm 2 above.

[0025] Furthermore, the aluminum alloy blank and aluminum alloy substrate for disks of the present invention comprise a core material and a sheath material disposed on at least one side of the core material. The core material contains Mn of 1.00% by mass or more and 10% by mass or less, and contains at least one of Mg of 3.0% by mass or less, Cr of 0.5% by mass or less, Zn of 0.4% by mass or less, and Cu of 0.4% by mass or less, with the balance comprising Al and unavoidable impurities. The number density of intermetallic compounds with a maximum length of 0.2 to 15.0 μm on the surface of the core material is 1.5 × 10⁻⁶. 5 pcs / mm 2 above.

[0026] Based on this structure, the internal friction of the aluminum alloy blank and the aluminum alloy substrate for the disk increases, enabling a high damping ratio.

[0027] Invention Effects

[0028] The aluminum alloy blank and aluminum alloy substrate for disks of the present invention can achieve a high damping ratio. Attached Figure Description

[0029] Figure 1 This is a graph showing the relationship between the number density and internal friction of intermetallic compounds with a maximum length of 0.2–15.0 μm. Detailed Implementation

[0030] The following describes in detail the methods used for implementing the present invention, including the aluminum alloy blank for disks (hereinafter referred to as the blank) and the aluminum alloy substrate for disks (hereinafter referred to as the substrate).

[0031] [Blank body]

[0032] The blank of this embodiment contains Mn within a specified range, and the balance consists of Al and unavoidable impurities.

[0033] Furthermore, in this embodiment, the number density of intermetallic compounds (hereinafter, appropriately referred to as "intermetallic compounds of specified size") with a maximum surface length of 0.2 to 15.0 μm in the blank body is at or above a specified value.

[0034] The following is a detailed explanation of each component.

[0035] (Mn: ≥1.00% by mass and ≤10% by mass)

[0036] Mn not only contributes to increased strength and yield strength, but also enhances the property of vibration damping (increasing the damping ratio). If the Mn content is below 1.00% by mass, the number density of intermetallic compounds of a specified size decreases, resulting in insufficient improvement in internal friction and inadequate enhancement of the damping ratio. On the other hand, if the Mn content is above 10% by mass, it may reduce machinability (grindability) and coarsen the intermetallic compounds, potentially further decreasing the number density of intermetallic compounds of a specified size.

[0037] Therefore, the Mn content is 1.00% by mass or more and 10% by mass or less.

[0038] From the viewpoint of improving the damping ratio, the Mn content is preferably 1.50% by mass or more, more preferably 1.80% by mass or more, 2.00% by mass or more, 2.50% by mass or more, or 3.00% by mass or more. Furthermore, from the viewpoint of machinability and preventing the coarsening of intermetallic compounds, the Mn content is preferably 8.00% by mass or less, more preferably 5.00% by mass or less or 4.00% by mass or less.

[0039] (Fe: less than 0.30% by mass)

[0040] Fe contributes to the improvement of strength and Young's modulus. However, compared with Mn, Fe cannot be expected to significantly improve the damping ratio. Moreover, if the Fe content is higher than 0.30% by mass, the intermetallic compounds will become coarser, the number density of intermetallic compounds of a specified size will decrease, and the damping ratio may decrease.

[0041] Therefore, although Fe is not an essential component, when Fe is included, its content is 0.30% by mass or less. From the viewpoint of preventing the coarsening of intermetallic compounds, the Fe content is preferably 0.25% by mass or less, more preferably 0.20% by mass or less, 0.10% by mass or less, 0.05% by mass or less, or 0.04% by mass or less.

[0042] Furthermore, when Fe is present as an unavoidable impurity, the Fe content is preferably 0.05% by mass or less, more preferably 0.03% by mass or less. Also, because Fe is an unavoidable impurity mixed into the raw material metal, high-purity raw material metals are required to reduce its content, resulting in high costs. Therefore, from a cost perspective, when Fe is present as an unavoidable impurity, the Fe content is preferably 0.005% by mass or more, more preferably 0.01% by mass or more.

[0043] (The balance is Al and unavoidable impurities)

[0044] The basic chemical composition of the billet constituting this embodiment is as described above, with the balance being Al and unavoidable impurities. Unavoidable impurities are those that inevitably mix in during the melting of the raw materials and are present within a range that does not impair the properties of the billet. Examples of unavoidable impurities include, for example, Ni, Ti, Na, Pb, Be, Ca, Zr, V, B, Sn, In, Cd, Bi, and Ge.

[0045] These unavoidable impurities, as long as each is below 0.005% by mass and the total is below 0.015% by mass, will not impair the effects of the present invention. Therefore, in the present invention, unavoidable impurities may be included within a range that does not impair the effects of the present invention. Furthermore, actively adding impurities within a range that does not impair the effects of the present invention will not hinder the effects of the present invention. In short, these methods are all included within the technical scope of the present invention.

[0046] Furthermore, the chemical composition of the billet in this embodiment can be achieved, for example, by appropriately adjusting the amount of elements added during the melting of the Al alloy. Additionally, the unavoidable content of impurities can be adjusted (limited), for example, by using raw material metal refined by a three-layer electrolysis method or by removing them using a segregation method.

[0047] (Number density of intermetallic compounds with a maximum length of 0.2–15.0 μm: 1.5 × 10⁻⁶) 5 pcs / mm 2 above)

[0048] The inventors' intensive research on the preform with the aforementioned chemical composition revealed that fine intermetallic compounds with a maximum surface length of less than 0.2 μm and coarse intermetallic compounds with a maximum surface length of more than 15.0 μm do not significantly affect internal friction. On the other hand, there is a strong positive correlation between the number density of intermetallic compounds with a maximum surface length of 0.2 to 15.0 μm and internal friction.

[0049] Specifically, if the number density of intermetallic compounds with a maximum surface length of 0.2–15.0 μm is 1.5 × 10⁻⁶, then... 5 pcs / mm 2 The above indicates a very high internal friction value, meaning it can achieve a very high damping ratio.

[0050] Therefore, the number density of intermetallic compounds with a maximum length of 0.2–15.0 μm is 1.5 × 10⁻⁶. 5 pcs / mm 2 That's all. From the viewpoint of improving internal friction, the number density of the intermetallic compound of this specified size is preferably 2.0 × 10⁻⁶. 5 pcs / mm 2 The above is preferred, and more preferably 2.5×10 5 pcs / mm 2 Above, 3.0×10 5 pcs / mm 2 Above, 3.3×10 5 pcs / mm 2 Above, 3.4×10 5 pcs / mm 2 above.

[0051] Furthermore, while there is no specific upper limit to the number density of intermetallic compounds of a given size, it is, for example, 20.0 × 10⁻⁶. 5 pcs / mm 2 Below, 10.0×10 5 pcs / mm 2 Below, 8.0×10 5 pcs / mm 2 Below, 5.0×10 5 pcs / mm 2 the following.

[0052] The number density of intermetallic compounds of a specified size on the surface of the billet can be controlled by the Mn content, the molten metal temperature, and the conditions of the homogenization heat treatment. Similarly, the number density of intermetallic compounds of a specified size on the surface of the substrate, as described later, can also be controlled.

[0053] Furthermore, the number density of intermetallic compounds of a specified size on the surface of the billet can be measured using a scanning electron microscope (SEM) after the surface is made into a mirror.

[0054] (Internal friction: 1.50×10) －3 above)

[0055] The internal friction of the billet in this embodiment is preferably 1.50 × 10⁻⁶. －3 The above. If the internal friction of the billet is 1.50 × 10⁻⁶... －3 The above methods can suppress disk vibrations during rotational drive by the internal friction of the material, making the improvement of vibration attenuation (increased damping ratio) more effective.

[0056] Furthermore, from the perspective of increasing the damping ratio, the internal friction is preferably 1.60 × 10⁻⁶. －3 The above is preferred, and more preferably is 1.70×10 －3 Above, 1.80×10 －3 above.

[0057] Furthermore, while there is no specific upper limit for internal friction, it is, for example, 5.00 × 10⁻⁶. －3 Below, 4.00×10 －3 Below, 3.00×10 －3 Below, 2.50×10 －3 Below, 2.00×10 －3 the following.

[0058] The internal friction of the billet, like the number density of intermetallic compounds of a specified size, can be controlled by the Mn content, the molten metal temperature, and the conditions of the homogenization heat treatment. The same applies to the internal friction of the substrate, which will be discussed later.

[0059] Then, the internal friction of the billet can be measured using an internal friction measuring device based on the half-peak full width method.

[0060] (Yield Strength)

[0061] While the yield strength of the billet in this embodiment is not particularly limited, from the viewpoint of improving impact resistance, it is preferred to be, for example, 150 MPa or more, and more preferably 155 MPa or more or 160 MPa or more. Furthermore, there is no particular limitation on the upper limit of the yield strength, but it is, for example, 220 MPa or less or 200 MPa or less.

[0062] The yield strength of the preform can be controlled by the Mn content. The same applies to the yield strength of the substrate, which will be discussed later.

[0063] Then, the yield strength of the billet can be obtained, for example, by making test pieces from the billet according to JIS Z 2241:2011 and conducting tensile tests on the metallic material.

[0064] [Base film]

[0065] The substrate of this embodiment is manufactured by cutting the end face of the blank of this embodiment (end face machining) and grinding the surface (main face) (mirror finish).

[0066] Also, the substrate is also called a polished substrate.

[0067] The substrate of this embodiment has the same chemical composition and structure as the blank of the present embodiment. Therefore, if the substrate of this embodiment is applied to a disk, even when the wall is thinned, it is possible to suppress the fine vibrations in the vertical direction (rotation axis direction) that occur when the disk is rotated.

[0068] Furthermore, the same applies to the chemical composition of the substrate, the number density of intermetallic compounds of a specified size, the numerical range of internal friction and yield strength.

[0069] [Method for manufacturing the billet]

[0070] Next, an example of the method for manufacturing the blank according to this embodiment will be described.

[0071] The billet of this embodiment, except for a few conditions, can be manufactured using common manufacturing methods and equipment, such as those used for manufacturing disk blanks. For example, the billet can be manufactured by a manufacturing method that sequentially includes the following steps: a casting step in which raw materials are melted, adjusted to a specified chemical composition, and the molten metal is cast into an ingot; a homogenization heat treatment step in which the cast ingot is subjected to homogenization heat treatment; a hot rolling step in which the heat-treated ingot is hot-rolled to obtain a hot-rolled sheet; a cold rolling step in which the hot-rolled sheet is cold-rolled to obtain a cold-rolled sheet; a punching step in which the cold-rolled aluminum alloy sheet is punched into a ring shape; and a straightening annealing step in which the punched substrate is straightened and annealed. Furthermore, intermediate annealing can be performed before or during the cold rolling step, as needed.

[0072] The following is a detailed explanation of each process.

[0073] (Casting process)

[0074] In the casting process, the raw material is melted at 700–800°C and cast using a known casting method. Furthermore, the cast ingot is preferably surface-cut, with a cutting amount of, for example, 2–40 mm per side.

[0075] Furthermore, the molten metal temperature (the temperature of the molten metal when it is poured into the mold) is generally around 670°C. By reaching 680°C or higher, coarse crystal precipitation can be avoided, and ultimately, the number density of intermetallic compounds of a specified size can be increased.

[0076] Furthermore, from the viewpoint of avoiding the precipitation of coarse crystals, the molten metal temperature is preferably 690°C or higher, and more preferably 700°C or higher.

[0077] Furthermore, when melting the Al alloy, it is preferable to blow an inert gas such as argon (Ar) into the molten metal to perform dehydrogenation treatment. In addition, the casting speed is preferably 30 to 80 mm / min.

[0078] (Homogenization heat treatment process)

[0079] In the homogenization heat treatment process, for example, the homogenization heat treatment is carried out at 430–620°C for 2 hours or more. Under such conditions, the intermetallic compounds can be fully dissolved. If the homogenization heat treatment temperature is below 430°C, or the homogenization heat treatment time is less than 2 hours, the intermetallic compounds become coarser, and the number of intermetallic compounds of a specified size decreases. On the other hand, if the homogenization heat treatment temperature is above 620°C, the surface of the ingot melts.

[0080] Therefore, from the viewpoint of increasing the number density of intermetallic compounds of a specified size, the homogenization heat treatment temperature is preferably 480°C or higher, more preferably 510°C or higher. On the other hand, from the viewpoint of suppressing melting on the surface of the ingot, it is preferably 600°C or lower, more preferably 580°C or lower. In addition, from the viewpoint of manufacturing efficiency, the homogenization heat treatment time is, for example, 25 hours or less, or 20 hours or less.

[0081] Furthermore, in the homogenization heat treatment process, when the first stage is a low-temperature range of 400 to 470°C and the second stage is a high-temperature range of higher than 470°C and lower than 630°C, (for example, the method described in Japanese Patent No. 6316511), in the first stage, intermetallic compounds precipitate or crystals grow and coarsen in size, and in the second stage, intermetallic compounds of a specified size do not precipitate. Ultimately, the number density of intermetallic compounds of the specified size decreases.

[0082] Therefore, in the homogenization heat treatment process, a single homogenization heat treatment is preferred.

[0083] (Hot rolling process)

[0084] In the hot rolling process, for example, the starting temperature of hot rolling can be 490°C or higher. Furthermore, the ending temperature of hot rolling can be 300–350°C. Hot rolling from 520°C to 400°C is preferably completed within 30 minutes, more preferably within 15 minutes. Additionally, the thickness of the hot-rolled sheet obtained can be, for example, 5 mm or less and 3 mm or less.

[0085] (Cold rolling process)

[0086] In the cold rolling process, cold rolling is performed to achieve the target sheet thickness of the billet. Specific sheet thicknesses, for example, range from 0.5 to 1.3 mm. Furthermore, intermediate annealing may be performed before or during cold rolling, as needed.

[0087] (Punching process)

[0088] In the stamping process, after the cold-rolled sheet is heat-treated as needed, the aluminum alloy sheet is stamped into the desired shape so that it can be used, for example, as a substrate for a 3.5-inch HDD or a substrate for a 2.5-inch HDD.

[0089] (Corrective annealing process)

[0090] In the straightening annealing process, substrates are stacked and clamped by partitions with high flatness, and annealing is performed while applying a load to the substrates. The annealing temperature is 250–500°C (preferably 300–400°C), and the holding time is, for example, 4–5 hours, but can be around 3 hours. The heating rate during straightening annealing is, for example, an average of 80°C / hour (Max. 150°C / hour), and during cooling, the annealing furnace door can be opened to allow for cooling.

[0091] Furthermore, as described above, the main difference between the blank and the substrate in this embodiment lies in whether or not grinding (mirror finishing) is performed. Therefore, the measurement results of the internal friction of the blank, the measurement results of the intermetallic compound, and the measurement results of the yield strength can be directly regarded as the measurement results of the substrate, and vice versa.

[0092] [Substrate manufacturing method]

[0093] The substrate of this embodiment can be manufactured, for example, by performing a manufacturing method that involves cutting the end face of the blank (end face machining) and grinding the surface of the blank (main face) (mirror finish machining).

[0094] [Disk disks and their manufacturing methods]

[0095] In the manufacturing process of a hard disk, firstly, the surface of a substrate is acid-etched to form an electroless Ni-P coating, and then its surface is ground (a substrate with an electroless Ni-P coating is also called a plated substrate). Secondly, on the surface of this substrate, a base film for improving magnetic properties, a magnetic film made of a Co-based alloy, and a protective film made of C (carbon) for protecting the magnetic film are formed by sputtering or other methods, thereby enabling the manufacture of a hard disk.

[0096] The formation of the electroless Ni-P coating, base film, magnetic film, and protective film can be carried out under the conditions typically implemented when manufacturing disks.

[0097] Furthermore, when manufacturing the blank and substrate, for example, the manufacturing conditions described in Japanese Patent No. 3471557 and Japanese Patent No. 5199714 can be used.

[0098] The disks manufactured in this way have a thickness of 0.5 to 1.3 mm. Furthermore, these disks are compatible with both 3.5-inch and 2.5-inch HDDs.

[0099] (Other processes)

[0100] The manufacturing method of the blank, substrate, and disk in this embodiment is as described above. However, to the extent that it does not have a negative impact on each of the processes, other processes may be included between or before and after each of the processes.

[0101] [Other Implementation Methods]

[0102] This concludes the description of embodiments in which the present invention is applied to single-layer materials. However, the present invention can also be applied to laminated materials having a "core material" and a "skin material" disposed on at least one side of the core material.

[0103] [Burnt material and substrate (other embodiments)]

[0104] Other embodiments of the blank and substrate have a laminated material structure, comprising a "core material" and a "skin material" disposed on at least one side of the core material.

[0105] Furthermore, when the blank and the substrate are laminated materials, it is preferable that the laminated material as a whole satisfies the requirements of "yield strength" and "internal friction" of the single-layer material.

[0106] (core material)

[0107] In other embodiments, the core material of the blank and substrate preferably meets the requirements of "composition of each component" and "number density of intermetallic compounds with a maximum surface length of 0.2 to 15.0 μm" of the single-layer material.

[0108] In addition, from the viewpoint of rollability and recyclability, the core material of the blank and substrate in other embodiments may also contain at least one of the following in addition to the "composition of each component" of the single-layer material: Mg: 3.0% by mass or less (preferably 1.5% by mass or less), Cr: 0.5% by mass or less (preferably 0.25% by mass or less), Zn: 0.4% by mass or less (preferably 0.2% by mass or less), and Cu: 0.4% by mass or less (preferably 0.10% by mass or less).

[0109] (Leather)

[0110] In other embodiments, the material of the blank and substrate is not particularly limited, but for example, it can be composed of Al-Mg system such as A5086 as specified in JIS H4000:2014.

[0111] Specifically, the leather contains Mg: 1.8% by mass or more and 7.0% by mass, Cr: 0.01% by mass or more and 0.35% by mass, Si: 0.1% by mass or less, Fe: 0.1% by mass or less, and contains at least one of Cu: 0.1% by mass or less and Zn: 0.4% by mass or less, with the balance consisting of Al and unavoidable impurities.

[0112] (Leather margin: Al and unavoidable impurities)

[0113] In other embodiments, the remaining composition of the blank and substrate material is Al and unavoidable impurities. Examples of unavoidable impurities include Mn, Ti, V, Zr, Ni, Na, Be, Ca, Pb, B, Sn, In, Cd, Bi, and Ge. Additionally, Si, Fe, Cu, and Zn may also be present as unavoidable impurities.

[0114] These unavoidable impurities, as long as each is below 0.005% by mass and the total is below 0.015% by mass, will not impair the effects of the present invention. Therefore, in the present invention, unavoidable impurities may be included within a range that does not hinder the effects of the present invention. Furthermore, when impurities are actively added within a range that does not hinder the effects of the present invention, the effects of the present invention are not impaired (in short, these methods are all included within the technical scope of the present invention).

[0115] (Coverage rate, etc.)

[0116] While there is no particular limitation on the thickness of the blank and substrate in other embodiments, it is acceptable to use 0.5 to 1.3 mm, similar to the case of single-layer material. Furthermore, the coverage ratio of the sheath material (the ratio of the thicknesses of each sheath material when the thickness of the laminated material is 100%) in other embodiments is 3 to 50%, preferably 5 to 30%.

[0117] [Method for manufacturing the billet (other embodiments)]

[0118] In other embodiments, the blanks, similar to those in the case of single-layer materials, can also be manufactured using manufacturing methods and equipment under normal conditions for manufacturing disk substrates, except for certain conditions.

[0119] For example, regarding the core material, the core material is manufactured by a manufacturing method that includes the following steps in sequence: a casting step, namely melting an Al alloy with the chemical composition and casting an ingot with the chemical composition adjusted; and a homogenization heat treatment step, namely performing homogenization heat treatment on the cast ingot.

[0120] Then, regarding the leather material, the leather material is manufactured by a manufacturing method that includes the following steps in sequence: a casting step, namely, melting the Al alloy with the chemical composition and casting an ingot with the chemical composition adjusted; a homogenization heat treatment step, namely, performing homogenization heat treatment on the cast ingot; and a hot rolling step, namely, hot rolling the ingot that has undergone homogenization heat treatment to obtain a hot-rolled plate.

[0121] A manufacturing method is capable of manufacturing a blank (laminated material) by sequentially including the following steps: an overlapping step in which the core material and the lining material are manufactured and then overlapped together; a homogenization heat treatment step in which the laminated material is subjected to homogenization heat treatment; a hot rolling step in which the laminated material is hot rolled; a cold rolling step in which the laminated material is rolled to the desired thickness; a punching step in which the cold rolled laminated material is punched into a ring shape; and a straightening annealing step in which the punched laminated material is straightened and annealed.

[0122] Furthermore, the conditions for each process are as follows.

[0123] In order to control the number density of intermetallic compounds with a maximum surface length of 0.2 to 15.0 μm, and to satisfy the conditions shown in the "casting process" and "homogenization heat treatment process" of the single-layer material, the casting process and homogenization heat treatment process of the core material are implemented.

[0124] Furthermore, the casting process, homogenization heat treatment process, and hot rolling process of the leather material can be implemented in a manner that satisfies the conditions shown in the "casting process", "homogenization heat treatment process", and "heat treatment process" of the single-layer material.

[0125] The overlapping methods in the overlapping process can be listed in existing well-known methods, such as the method of binding belts at both ends of the core material and the leather material, and the method of welding and fixing.

[0126] For homogenization heat treatment of laminated materials, it can be carried out, for example, at 500-550°C for 1-20 hours.

[0127] For hot rolling of laminated materials, it can be carried out, for example, with a starting temperature of 510 to 540°C and a time of less than 30 minutes from the end of the homogenization heat treatment to the end of the hot rolling.

[0128] For cold rolling of laminated materials, for example, it can be carried out in a way that makes the sheet thickness 0.5 to 1.3 mm.

[0129] Furthermore, the blanking process for laminated materials can be performed in a manner that satisfies the conditions shown in the "Blanking Process" for single-layer materials. Additionally, the straightening annealing process for laminated materials can also be performed in a manner that satisfies the conditions shown in the "Straightening Annealing Process" for single-layer materials, but the holding time can be set to be as long as 7 to 9 hours.

[0130] Furthermore, the slicing milling method described in paragraph 0048 of Japanese Patent No. 5271094 can also be applied to the manufacturing methods of the core material and the sheath material. Specifically, the Al alloy used for casting the core material and the Al alloy used for the sheath material are melted separately, and the resulting ingots are subjected to surface cutting and homogenization heat treatment to manufacture ingots for the sheath material and ingots for the core material (core material), respectively. Then, the ingots for the sheath material are further subjected to surface cutting and homogenization heat treatment, and then sliced ​​to the desired thickness for manufacturing. In this case, it is necessary to control the homogenization heat treatment conditions and hot rolling conditions after the overlapping process in a manner that appropriately satisfies the conditions shown for the single-layer material.

[0131] Then, the method for manufacturing substrates and disks using blanks (laminated materials) is the same as that for single-layer materials.

[0132] Example

[0133] The following description illustrates specific embodiments of the present invention. However, the scope of the present invention is not limited thereto.

[0134] [Example 1: Single-layer material]

[0135] [Preparation of test materials]

[0136] First, the material is melted and its composition is adjusted to the chemical composition shown in Table 1. This molten metal is then poured into a mold measuring 50 mm thick × 145 mm wide × 200 mm long to create a slab. The temperature of the molten metal (the temperature at which it is poured into the mold) is approximately 720°C. Next, a 2 mm surface cut is performed on both sides (thickness direction) of the resulting slab. Subsequently, a homogenization heat treatment is performed at the temperature and time shown in the table. Then, hot rolling is carried out until a thickness of 5 mm is achieved (starting temperature: approximately 510°C), followed by cold rolling until a thickness of 0.7 mm is achieved (material temperature not exceeding 100°C).

[0137] The cold-rolled sheet is then punched into 3.5-inch rings (approximately 95 mm outer diameter and 25 mm inner diameter), stacked, and subjected to straightening annealing. The straightening annealing is performed by holding the rings at 350°C for 3 hours.

[0138] Subsequently, a blank (0.7mm thick) for a 3.5-inch HDD is manufactured by peeling. Next, the end faces of each blank are machined. Then, the surfaces of the blanks (both sides) are ground to 10μm on one side (mirror finish) using a PVA grinding stone (4000, manufactured by Nippon Tokuken Co., Ltd.) to manufacture a substrate (0.7mm thick).

[0139] Using the manufactured blank or substrate, measure the number density, internal friction, and yield strength (reference) of intermetallic compounds with a maximum surface length of 0.2–15.0 μm.

[0140] These measurements were performed in the following manner.

[0141] [Measurement Method]

[0142] (1) Number density of intermetallic compounds with a maximum length of 0.2–15.0 μm

[0143] The surface of the blank was machined with a diamond turning tool to achieve a mirror finish. Ten fields of view (1 field of view: 60μm × 45μm) were captured at 2000x magnification using an FE-SEM (JSM-7001F, manufactured by JEOL Ltd., with built-in particle analysis software EX-35110, version 3.84 as described in the version notes, accelerating voltage 15kV). These were used to obtain a COMPO image. The COMPO image was then analyzed using Image-Pro PLUS J Version 6.1.0.372. A threshold was set at the gray matrix portion; areas lighter than the matrix (parent phase) were considered intermetallic compounds. The absolute maximum length of each compound was measured (the maximum distance between any two points on the particle outline). The number of intermetallic compounds with a maximum length of 0.2–15.0μm was then counted, and the number density per unit area was calculated.

[0144] In the table, intermetallic compounds with a maximum length of 0.2–15.0 μm are found in 1.5 × 10⁻⁶ μm. 5 pcs / mm 2 The above is represented as "0", and less than 1.5 × 10 5 pcs / mm 2 The symbol for is “×”.

[0145] (2) Internal friction

[0146] Test pieces (10mm wide × 60mm long × 0.7mm thick, with the longitudinal direction roughly parallel to the rolling direction) were cut from the billet. Internal friction was measured using an internal friction measuring device (JE2-RT manufactured by Technoplus, Japan; measurement software: JE-RT control software Version 2.6.1). Then, for each test piece, the average value of the internal friction obtained from three measurements was calculated and displayed in a table as the internal friction value for each billet.

[0147] The internal friction measurement method employs the full width at half maximum (FWHM) method. Furthermore, the detailed specifications for the internal friction measurement device are as follows: Measurement method: free resonance; Measurement temperature: room temperature (approximately 24±2℃); Measurement atmosphere: air; Vibration method: non-contact electrostatic vibration; Test method: two-point suspension method (the test piece is held at two points 13.44 mm from both ends of the longitudinal direction by suspension lines); Detection method: acoustic detection; Scanning step during the test: 0.02 Hz; Scanning range: arbitrarily set (arbitrarily set within the range of 950–1100 Hz based on the stable values ​​obtainable by the FWHM method, with a scanning range width of 30–100 Hz).

[0148] Then, the internal friction is 1.5 × 10. －3 The above damping ratios are rated as "0" (qualified), and the internal friction is less than 1.5 × 10⁻⁶. －3 The damping ratio is rated as "×" (unacceptable).

[0149] (3) Yield strength: Reference

[0150] JIS 13B test pieces were cut from the billet with the stretching direction parallel to the rolling direction. Using these test pieces, tensile tests were performed according to JIS Z 2241:2011 (residual deformation method: offset method) to determine the yield strength (0.2% yield strength). The stretching speeds were 3 mm / min (up to 0.5% strain) and 20 mm / min (after 0.5% strain).

[0151] Additionally, yield strength is shown as a reference.

[0152] The table shows the chemical composition of the preform and substrate, and the results of the measurements or evaluations described in (1) to (3). Additionally, underlines in the table indicate items that do not meet the requirements of this invention.

[0153] Table 1

[0154]

[0155] [Discussion of Results]

[0156] (Table-based discussion)

[0157] As shown in Table 1, since Nos. 1 to 3 and 6 meet the requirements of this invention, they have high internal friction, which is a result of qualified damping ratio (high damping ratio). In addition, Nos. 1 to 3 and 6 show high yield strength values.

[0158] On the other hand, No.4 has low Mn content and low number density of specified intermetallic compounds on the surface, resulting in low internal friction and an unqualified damping ratio.

[0159] In addition, No.5 has low internal friction due to the low temperature of the homogenization heat treatment and the low number density of the specified intermetallic compounds on the surface, resulting in an unqualified damping ratio.

[0160] (Discussion based on diagrams)

[0161] Figure 1 The diagram shown is based on internal friction η (×10 －3 Using ) as the vertical axis, the number density (×10) of intermetallic compounds with a maximum length of 0.2–15.0 μm. 5 pcs / mm 2 Plot the results of No. 1 to No. 6 using π as the horizontal axis.

[0162] By this Figure 1 The results confirm a very strong positive correlation between the number density of intermetallic compounds with a maximum surface length of 0.2–15.0 μm and internal friction.

[0163] In addition, by Figure 1 The results confirm that if the number density of intermetallic compounds with a maximum surface length of 0.2–15.0 μm is within 1.5 × 10⁻⁶ μm... 5 pcs / mm 2 Therefore, the internal friction η is 1.5 × 10⁻⁶. －3 above.

[0164] (Discussion on SEM images)

[0165] The SEM image obtained when measuring the number density of intermetallic compounds of a specified size is an image shown below when visually confirmed.

[0166] SEM images No. 1 through 3 and 6 show a uniformly dispersed state of many intermetallic compounds of a specified size. In SEM image No. 1, no large intermetallic compounds were identified. In SEM image No. 3, due to the relatively high Mn content, some large intermetallic compounds were present, but a sufficient number of intermetallic compounds of the specified size were still identified.

[0167] In SEM image No. 4, due to the low Mn content, the number density of intermetallic compounds of the specified size can be confirmed to be low. However, no large intermetallic compounds can be identified in SEM image No. 4.

[0168] In the SEM image of No. 5, due to the low temperature of the homogenization heat treatment, multiple coarse intermetallic compounds were produced, resulting in a low number density of intermetallic compounds of a specified size.

[0169] [Example 2: Laminated Material]

[0170] [Preparation of test materials]

[0171] First, the core material is melted and its composition is adjusted to the chemical composition shown in Table 2, No. 11. The mold is then used to cast the ingot (book-shaped mold). The mold dimensions are 50mm high × 145mm wide × 200mm long, and the casting temperature is 720℃.

[0172] Next, the two sides of the obtained casting were subjected to a 13mm surface cut and homogenization heat treatment under the conditions shown in Table 2.

[0173] In addition, the material for melting the leather is prepared with the following composition: Si: 0.01% by mass, Fe: 0.017% by mass, Cu: 0.04% by mass, Mg: 4.0% by mass, Cr: 0.07% by mass, Zn: 0.15% by mass, with the balance being Al and unavoidable impurities. The ingot is then cast using a mold (book-shaped mold). The mold dimensions are 50mm high × 145mm wide × 200mm long, and the casting temperature is 720℃.

[0174] Next, the two sides of the obtained casting were cut by 2 mm and then subjected to homogenization heat treatment at 540℃ for 4 hours.

[0175] Subsequently, the time from the end of the homogenization heat treatment (when the material is removed from the homogenization furnace) to the end of the hot rolling is 3 minutes, and the material after homogenization heat treatment is hot rolled (starting temperature 540℃, finishing thickness 3mm).

[0176] Then, the leather (3mm thick), core material (24mm thick), and leather (3mm thick) are welded together to form a three-layer covering material.

[0177] Then, the cladding material is placed in a furnace at 540°C and subjected to a homogenization heat treatment for 1 hour and 30 minutes after reaching 540°C. Following this, hot rolling (3mm finish thickness) is performed, with the time from the end of the homogenization heat treatment to the end of hot rolling being 3 minutes. Next, the resulting hot-rolled sheet is cold-rolled. The cold rolling process involves passing the material through multiple passes at a temperature not exceeding 100°C, ultimately achieving a sheet thickness of 0.5mm.

[0178] Furthermore, the thickness ratio of the leather, core material, and leather is approximately 10%:80%:10%.

[0179] The cold-rolled sheet is then punched into 3.5-inch rings (approximately 95 mm outer diameter and 25 mm inner diameter), stacked, and subjected to straightening annealing. The straightening annealing is performed by holding the rings at a temperature between 260°C and 320°C for 8 hours.

[0180] Subsequently, a blank (0.5mm thick) for the No.11 3.5-inch HDD is manufactured by peeling it off.

[0181] Then, using the manufactured No.11 blank, the yield strength and internal friction were evaluated using the same method as in Example 1.

[0182] In addition, regarding the number density of intermetallic compounds on the core material surface, a rotary polisher (TegraPol-35 manufactured by Struers) was used to grind the material mechanically (using sandpaper) until the outer layer could be removed (grinding to a plate thickness of 0.437 mm). Then, a rotary polisher (Labopol-30 manufactured by Struers) was used to polish and refine the surface. The measurements were then taken using the same method as in Example 1.

[0183] The table shows the composition and yield strength of the core material of the billet. Also, underlines in the table indicate items that do not meet the requirements specified in this invention.

[0184] Table 2

[0185]

[0186] (Results of the study: Results in Table 2)

[0187] As shown in Table 2, the core material of No. 11 has high internal friction as a laminate because it meets the requirements of this invention, which is a result of qualified damping ratio (high damping ratio).

[0188] The foregoing has provided a detailed description of the embodiments and examples of the present invention. However, the spirit of the present invention is not limited to the content described, and its scope of rights must be interpreted based on the scope of the patent claims. Furthermore, the content of the present invention can, of course, be changed or modified based on the description.

[0189] Furthermore, this application is based on Japanese patent applications filed on March 14, 2019 (Takumi 2019-047221) and January 10, 2020 (Takumi 2020-002934), the contents of which are incorporated herein by reference.

Claims

1. An aluminum alloy blank for a hard disk, characterized in that, Include Mn: ≥1.00% by mass and ≤10% by mass Fe: ≥0.005% by mass and ≤0.30% by mass Mg: 0.005% by mass or more and 1.5% by mass or less Cr: ≥0.005% by mass and ≤0.25% by mass Zn: ≥0.005% by mass and ≤0.2% by mass Cu: ≥0.005% by mass and ≤0.10% by mass The balance includes Al and unavoidable impurities. In the surface, the number density of intermetallic compounds with a maximum length of 0.2–15.0 μm is 1.5 × 10⁻⁶. 5 pcs / mm 2 above.

2. An aluminum alloy substrate for a hard disk, characterized in that, Include Mn: ≥1.00% by mass and ≤10% by mass Fe: ≥0.005% by mass and ≤0.30% by mass Mg: 0.005% by mass or more and 1.5% by mass or less Cr: ≥0.005% by mass and ≤0.25% by mass Zn: ≥0.005% by mass and ≤0.2% by mass Cu: ≥0.005% by mass and ≤0.10% by mass The balance includes Al and unavoidable impurities. In the surface, the number density of intermetallic compounds with a maximum length of 0.2–15.0 μm is 1.5 × 10⁻⁶. 5 pcs / mm 2 above.

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