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

Abstract

Provided are an aluminum alloy plate for a magnetic disk, an aluminum alloy plate blank for a magnetic disk, and an aluminum alloy plate base sheet for a magnetic disk, which have good rigidity and are capable of suppressing thermal deformation during sputtering of a magnetic film. An aluminum alloy sheet for a magnetic disk, which contains 0.1-7.0 mass% of Mg, 0.005-1.0 mass% of Cr, 3-100 mass ppm of Be, Mn, 100 mass ppm or less of Ti, 0.20 mass% or less of Si, and 0.03-5.9 mass% in total of at least one of Fe, Mn and Ni, the remainder being Al and impurities, and the Mn solid solution content in the aluminum matrix being 0.03 mass% or more.

Description

Technical Field

[0001] The present invention relates to an aluminum alloy plate for magnetic disk, an aluminum alloy blank for magnetic disk and an aluminum alloy substrate for magnetic disk. Background Art

[0002] With the digitization of information and the spread of the Internet, a large amount of digital data needs to be processed, and data centers are focusing on the demand for larger capacity hard disk drives (HDDs). In order to increase the capacity of HDDs, research is being conducted on thinner disks in order to increase the number of disks that can be installed in each HDD.

[0003] However, when the magnetic disk is driven to rotate, especially when the data transmission speed is to be increased at a high rotation speed, the probability of occurrence of micro vibrations increases as the magnetic disk is thinner.

[0004] One of the methods for suppressing the vibration of the magnetic disk with such a thin wall is to increase the rigidity of the substrate.

[0005] For example, Patent Documents 1 and 2 adopt a chemical composition in which at least one of Fe, Mn, and Ni is added in a specific amount to an aluminum alloy plate in order to improve the rigidity of the substrate, thereby improving the rigidity of the substrate itself of the magnetic disk.

[0006] In addition, regarding substrates for magnetic disks, the index of "flatness" is a very important index because it largely affects the performance of hard disk drives (HDDs) using the substrates.

[0007] In the production process of substrates, there is a concern about deformation due to thermal strain. This deformation has an adverse effect on the flatness of the substrate and becomes a factor causing defective products.

[0008] At present, from the perspective of resource depletion, the reuse of various materials is progressing, and the recycling of metals that are consumed in large quantities has been carried out from the past. The above-mentioned defective products can also be reused through recycling, but it is important to suppress the occurrence of defective products by suppressing thermal strain.

[0009] For example, Patent Document 3 describes an aluminum alloy plate for a magnetic disk having excellent flatness, which has a specific chemical composition and a compound number gradient in the plate thickness direction that is equal to or greater than a specific value.

[0010] Here, as shown in Patent Document 4, in the magnetic disk substrate, thermal expansion during sputtering of the magnetic film causes thermal strain to occur around the clamping portion. Therefore, in order to realize a magnetic disk with excellent flatness, it is necessary to suppress deformation caused by thermal strain of the magnetic disk substrate.

[0011] In terms of suppressing deformation caused by thermal strain, for example, Patent Document 5 describes that by adopting a cover aluminum alloy plate having a specific chemical composition and a yield strength difference in a direction parallel to rolling before and after heat treatment of more than a specific value, excellent stress relaxation resistance can be exhibited and thermal deformation can be suppressed.

[0012] Prior art literature

[0013] Patent Literature

[0014] Patent Document 1: Japanese Patent No. 7132289

[0015] Patent Document 2: Japanese Patent No. 6684139

[0016] Patent Document 3: Japanese Patent Application Publication No. 2023-004878

[0017] Patent Document 4: Japanese Patent Application Publication No. 2022-010156

[0018] Patent Document 5: Japanese Patent Application Publication No. 2021-011621 Summary of the invention

[0019] Problems to be solved by the invention

[0020] Therefore, in aluminum alloy plates for magnetic disks, both good rigidity and suppression of thermal deformation are important, but there is still room for research on aluminum alloy plates for magnetic disks that achieve both.

[0021] The present invention has been made in view of the above problems, and an object thereof is to provide an aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk which have good rigidity and can suppress thermal deformation during sputtering of a magnetic film.

[0022] Means of solving the problem

[0023] As a result of repeated studies, the inventors discovered that by adopting a specific alloy composition and making the Mn solid solution content in the aluminum matrix phase greater than 0.03 mass %, an aluminum alloy plate for a magnetic disk having good rigidity and capable of suppressing thermal deformation during sputtering of the magnetic film can be obtained, thereby creating the present invention.

[0024] That is, the present invention relates to the following contents.

[0025] [1] An aluminum alloy plate for a magnetic disk, comprising

[0026] Mg: 0.1-7.0% by mass

[0027] Cr: 0.005-1.0 mass%,

[0028] Be: 3 to 100 mass ppm,

[0029] Mn, and

[0030] Ti: 100 mass ppm or less,

[0031] Si: 0.20 mass % or less,

[0032] The total amount of Fe, at least one of Mn and Ni is 0.03 to 5.9 mass %.

[0033] The balance contains Al and impurities,

[0034] The amount of Mn dissolved in the aluminum matrix phase is 0.03 mass % or more.

[0035] [2] The aluminum alloy plate for a magnetic disk according to [1], comprising at least one of 0 to 1.00 mass % of Fe, 0.03 to 1.4 mass % of Mn, and 0 to 3.5 mass % of Ni.

[0036] [3] The aluminum alloy plate for a magnetic disk according to [1] or [2], further comprising at least one of 1.0 mass % or less of Cu and 1.0 mass % or less of Zn.

[0037] [4] The aluminum alloy plate for a magnetic disk according to [1] or [2], wherein the Young's modulus is 70 GPa or more.

[0038] [5] The aluminum alloy plate for a magnetic disk according to [1] or [2], wherein the stress relaxation rate is 90% or less.

[0039] [6] An aluminum alloy blank for a magnetic disk, obtained from the aluminum alloy plate for a magnetic disk described in [1] or [2].

[0040] [7] An aluminum alloy substrate for a magnetic disk, obtained from the aluminum alloy blank for a magnetic disk described in [6].

[0041] Effects of the Invention

[0042] According to the present invention, it is possible to provide an aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk which have excellent rigidity and can suppress thermal deformation during sputtering of a magnetic film. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 (a) and Figure 1 (b) is a diagram for explaining the stress relaxation rate measurement in the example. DETAILED DESCRIPTION

[0044] Hereinafter, an aluminum alloy plate for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk according to an embodiment of the present invention will be described.

[0045] In the following description, the aluminum alloy plate for a magnetic disk, the aluminum alloy blank for a magnetic disk, and the aluminum alloy substrate for a magnetic disk according to the present embodiment may be simply referred to as “aluminum alloy plate”, “blank”, or “substrate”, respectively.

[0046] [Aluminum alloy plate for magnetic disk]

[0047] The aluminum alloy plate for magnetic disks of the present embodiment contains Mg: 0.1-7.0 mass%, Cr: 0.005-1.0 mass%, Be: 3-100 mass ppm, Mn, Ti: 100 mass ppm or less, Si: 0.20 mass % or less, Fe, at least one of the above-mentioned Mn and Ni is 0.03-5.9 mass % in total, the balance includes Al and impurities, and the Mn solid solution amount in the aluminum matrix is ​​0.03 mass % or more. In addition, the aluminum alloy plate for magnetic disks of the present embodiment may also contain Cu and Zn.

[0048] Hereinafter, each structure of the aluminum alloy plate for a magnetic disk according to the present embodiment will be described in detail.

[0049] (Mg: 0.1 mass % or more and 7.0 mass % or less)

[0050] Mg is an essential constituent element of the aluminum alloy plate for a magnetic disk according to the present embodiment, and is contained in the aluminum alloy plate in order to obtain good yield strength.

[0051] If the Mg content in the aluminum alloy plate is less than 0.1 mass %, the above effect cannot be achieved. On the other hand, if the Mg content in the aluminum alloy plate is higher than 7.0 mass %, the rigidity decreases. Therefore, the Mg content is 0.1 mass % or more and 7.0 mass % or less.

[0052] In addition, from the viewpoint of improving the yield strength, the Mg content is preferably 0.5 mass % or more, 1.0 mass % or more, 1.5 mass % or more, 1.7 mass % or more, 2.0 mass % or more, 2.2 mass % or more, 2.5 mass % or more. In addition, from the viewpoint of suppressing the reduction of rigidity, it is preferably 6.5 mass % or less, 6.0 mass % or less, 5.5 mass % or less, 5.0 mass % or less, 4.5 mass % or less, 4.0 mass % or less, 3.5 mass % or less.

[0053] (Cr: 0.005 mass % or more and 1.0 mass % or less)

[0054] Cr is an essential constituent element of the aluminum alloy plate for a magnetic disk according to the present embodiment, and is contained in the aluminum alloy plate in order to obtain good yield strength.

[0055] If the Cr content in the aluminum alloy plate is less than 0.005 mass %, the above-mentioned effect cannot be achieved. On the other hand, if the Cr content is higher than 1.0 mass %, the intermetallic compound coarsens, edge cracks occur, and there is a possibility of reduced rollability. Therefore, the Cr content is 0.005 mass % or more and 1.0 mass % or less.

[0056] In addition, from the viewpoint of improving the yield strength, the Cr content is preferably 0.01 mass % or more, 0.03 mass % or more, 0.05 mass % or more, 0.08 mass % or more, or 0.1 mass % or more. In addition, from the viewpoint of ensuring the rollability, it is preferably 0.9 mass % or less, 0.8 mass % or less, 0.7 mass % or less, 0.6 mass % or less, 0.5 mass % or less, 0.4 mass % or less, 0.3 mass % or less, or 0.2 mass % or less.

[0057] (Be: 3 mass ppm or more and 100 mass ppm or less)

[0058] Be is an essential constituent element of the aluminum alloy plate for magnetic disks of the present embodiment, and has the effect of forming an oxide film during casting to suppress the formation of Mg oxides. In addition, it has the effect of improving the hot rolling property and formability of the aluminum alloy, and also has the effect of reducing the adhesion between the blanks caused by oxidation inhibition during the correction annealing, thereby suppressing the deterioration of flatness caused by external force during subsequent peeling, and can make the flatness excellent.

[0059] If the Be content is less than 3 mass ppm, the effect of adding Be cannot be fully obtained. On the other hand, if the Be content is more than 100 mass ppm, the compound containing Be becomes coarse, edge cracking occurs, and there is a possibility that the rolling property is reduced. Therefore, the Be content is 3 mass ppm or more and 100 mass ppm or less.

[0060] In addition, from the viewpoint of fully obtaining the effect of the above-mentioned Be addition, the Be content is preferably 4 mass ppm or more, 5 mass ppm or more, 8 mass ppm or more, 10 mass ppm or more. In addition, from the viewpoint of ensuring the rollability, it is preferably 80 mass ppm or less, 50 mass ppm or less, 30 mass ppm or less, 20 mass ppm or less.

[0061] (Ti: 100 mass ppm or less)

[0062] Ti is contained in a small amount in the aluminum alloy plate to refine the grains of the aluminum alloy ingot and obtain good yield strength. However, if the content of Ti exceeds 100 mass ppm, the intermetallic compound will coarsen and edge cracks will occur, which may reduce the rollability. Therefore, the content of Ti is 100 mass ppm or less (including 0.00 mass ppm).

[0063] In addition, from the viewpoint of suppressing the reduction of rolling properties, the content of Ti is preferably 90 mass ppm or less, 80 mass ppm or less, 70 mass ppm or less, 60 mass ppm or less, 50 mass ppm or less, 40 mass ppm or less, or 30 mass ppm or less. Even if the content of Ti is 0 mass ppm, the characteristics of the present invention are not impaired, but if contained, from the viewpoint of improving the yield strength, the content of Ti is preferably 5 mass ppm or more, 10 mass ppm or more.

[0064] (Si: 0.20 mass % or less)

[0065] Si is usually mixed into aluminum alloys as an inevitable impurity in the ingot, forming simple Si, Al-Fe-Si intermetallic compounds, etc. If the Si content exceeds 0.20 mass%, the Young's modulus decreases, or the simple Si and Al-Fe-Si intermetallic compounds become coarse, and the rolling properties decrease. Therefore, the Si content is 0.20 mass% or less (including 0.00 mass%).

[0066] In addition, from the viewpoint of suppressing the reduction of Young's modulus and rolling property, the content of Si is preferably 0.18% by mass or less, 0.15% by mass or less, 0.13% by mass or less, 0.10% by mass or less, 0.08% by mass or less, 0.05% by mass or less, 0.04% by mass or less, 0.03% by mass or less, 0.02% by mass or less. The lower the content of Si, the better, even if it is 0% by mass, the characteristics of the present invention are not impaired, but because high-purity raw materials (Al ingots and intermediate alloy ingots, etc.) are required, the cost increases. Therefore, the content of Si is preferably 0.004% by mass or more in industry.

[0067] (Total of Fe, Mn and Ni: 0.03 to 5.9 mass %)

[0068] Fe, Mn and Ni are components that contribute to improving rigidity and stress relaxation resistance. Therefore, in the aluminum alloy plate for magnetic disks of the present embodiment, the total content of at least one selected from the group consisting of Fe, Mn and Ni is 0.03 to 5.9 mass %, and the Mn solid solution content in the aluminum matrix is ​​0.03 mass % or more. That is, it may contain Fe and Mn, or both Mn and Ni, or it may contain all of Fe, Mn and Ni, and there is no particular limitation as long as the total content is 0.03 to 5.9 mass %.

[0069] In addition, in order to obtain good rigidity and stress relaxation resistance, the total content of Fe, Mn and Ni is preferably 0.05 mass %, 0.06 mass %, 0.10 mass %, 0.2 mass %, 0.3 mass %, 0.5 mass %, 0.8 mass %, 1.0 mass %. On the other hand, if it is excessively contained, it is possible that the compound is coarsened and the plating property is reduced. Therefore, the total content is preferably 5.5 mass %, 5.0 mass %, 4.5 mass %, 4.0 mass %, 3.5 mass %, 3.0 mass %, 2.5 mass %, 2.0 mass %, 1.5 mass %.

[0070] Furthermore, the aluminum alloy plate for a magnetic disk according to the present embodiment preferably contains at least one of 0 to 1.00 mass % of Fe, 0.03 to 1.4 mass % of Mn, and 0 to 3.5 mass % of Ni.

[0071] (Fe: 1.00 mass % or less)

[0072] Fe is contained in the aluminum alloy plate to obtain good rigidity and stress relaxation resistance. On the other hand, if the Fe content in the aluminum alloy plate is higher than 1.00 mass %, the compound may coarsen and the plating property may be reduced. Therefore, the Fe content is 1.00 mass % or less (including 0 mass %).

[0073] In addition, from the viewpoint of suppressing the reduction of the plating property, the Fe content is preferably 0.90 mass % or less, 0.80 mass % or less, 0.70 mass % or less, 0.60 mass % or less, 0.50 mass % or less. In addition, from the viewpoint of obtaining good rigidity and stress relaxation resistance, it is preferably 0.01 mass % or more, 0.02 mass % or more, 0.05 mass % or more, 0.10 mass % or more, 0.15 mass % or more, 0.25 mass % or more, 0.30 mass % or more, 0.35 mass % or more, 0.40 mass % or more.

[0074] (Mn: 0.03 mass % or more)

[0075] In the aluminum alloy plate for a magnetic disk according to the present embodiment, the amount of Mn dissolved in the aluminum matrix phase is 0.03 mass % or more.

[0076] Mn is contained in the aluminum alloy plate to obtain good rigidity and stress relaxation resistance. On the other hand, if the Mn content in the aluminum alloy plate is 1.4 mass % or less, it is possible to prevent the compound from coarsening and reducing the plating property. Therefore, the Mn content is preferably 1.4 mass % or less (including 0 mass %).

[0077] In addition, from the viewpoint of suppressing the reduction of the plating property, the Mn content is preferably 1.3 mass % or less, 1.2 mass % or less, 1.1 mass % or less, 1.0 mass % or less, 0.9 mass % or less, 0.8 mass % or less, 0.7 mass % or less, 0.6 mass % or less. In addition, from the viewpoint of obtaining good rigidity and stress relaxation resistance, it is preferably 0.06 mass % or more, 0.1 mass % or more, 0.2 mass % or more, 0.3 mass % or more, 0.4 mass % or more, 0.5 mass % or more.

[0078] (Ni: 3.5 mass % or less)

[0079] Ni is contained in the aluminum alloy plate to obtain good rigidity and stress relaxation resistance. On the other hand, if the Ni content in the aluminum alloy plate is higher than 3.5 mass %, the compound may coarsen and the plating property may be reduced. Therefore, the Ni content is 3.5 mass % or less (including 0 mass %).

[0080] In addition, from the viewpoint of suppressing the reduction of plating property, the Ni content is preferably 3.0 mass % or less, 2.5 mass % or less, 2.0 mass % or less, 1.5 mass % or less, 1.0 mass % or less, 0.9 mass % or less, 0.8 mass % or less, 0.7 mass % or less, 0.6 mass % or less, 0.5 mass % or less. In addition, from the viewpoint of obtaining good rigidity and stress relaxation resistance, it is preferably 0.1 mass % or more, 0.2 mass % or more, 0.3 mass % or more, 0.4 mass % or more.

[0081] (Cu: 1.0 mass % or less, Zn: 1.0 mass % or less)

[0082] Cu and Zn are components that expand the solid-liquid coexistence area and help reduce the frequency of sparking during casting. In addition, they are components that have the effect of uniformly precipitating zinc during zincate treatment, and also help improve the smoothness of the coating. On the other hand, if Cu and Zn are contained excessively, the smoothness of the above-mentioned coating may deteriorate. In addition, the smoothness of the electroless Ni-P plating formed on the surface may be reduced. Therefore, in the aluminum alloy plate for magnetic disks of this embodiment, it is preferred to also contain at least one of Cu: 1.0 mass % or less and Zn: 1.0 mass % or less.

[0083] From the viewpoint of suppressing the reduction of the plating smoothness, the content of Cu is preferably 1.0 mass % or less, 0.75 mass % or less, 0.50 mass % or less, 0.35 mass % or less, 0.25 mass % or less, 0.20 mass % or less, 0.10 mass % or less, 0.05 mass % or less. In addition, although Cu may not be included, if it is included, from the viewpoint of reliably obtaining the effect brought by adding Cu, it is preferably 0.005 mass % or more.

[0084] From the viewpoint of suppressing the reduction of the smoothness of the coating, the content of Zn is preferably 1.0 mass % or less, 0.75 mass % or less, 0.50 mass % or less, 0.35 mass % or less, 0.25 mass % or less, 0.20 mass % or less, 0.10 mass % or less, 0.05 mass % or less. In addition, although Zn may not be contained, if contained, it is preferably 0.005 mass % or more from the viewpoint of reliably obtaining the effect brought about by the addition of Zn.

[0085] (Breakdown: Al and impurities)

[0086] The aluminum alloy plate of the present embodiment may contain elements other than the above as impurities according to the selection of the raw materials melted during the manufacture of the ingot. Specifically, Zr, V, B, Na, K, Ca, Pb, P, Sn, Ag, Bi, In, Ge, Sr, Cd, etc. can be cited as impurity elements. Among them, Zr and V are each limited to less than 0.10 mass%, and B, Na, K, Ca, Pb, P, Sn, Ag, Bi, In, Ge, Sr, and Cd are each limited to less than 0.05 mass%. If these elements are within this range, not only when they are contained as unavoidable impurities, but also when they are actively added by intentionally increasing the blending ratio of scrap containing these elements, the effect of the present embodiment is not hindered.

[0087] When each element shown as an impurity element is inevitably contained (that is, when it is an inevitable impurity), the content of each element is preferably 0.005 mass % or less, and the total amount of each element is preferably 0.015 mass % or less.

[0088] When the chemical composition is adopted without adding the above-mentioned Si, Fe, Ni, Cu, and Zn, the content of each of these inevitable impurities is preferably 0.005 mass % or less.

[0089] <Mn solid solution amount in aluminum matrix: 0.03 mass % or more>

[0090] The greater the amount of Mn dissolved in the aluminum matrix, the better stress relaxation resistance can be obtained. If the amount of Mn dissolved in the aluminum matrix is ​​0.03 mass % or more, good stress relaxation resistance can be obtained, preferably 0.04 mass % or more, 0.05 mass % or more, 0.06 mass % or more, 0.07 mass % or more, 0.08 mass % or more, 0.09 mass % or more, 0.10 mass % or more, 0.11 mass % or more, 0.12 mass % or more, 0.13 mass % or more, 0.14 mass % or more, 0.15 mass % or more, 0.16 mass % or more, 0.17 mass % or more, 0.18 mass % or more, 0.19 mass % or more, 0.20 mass % or more, 0.21 mass % or more, 0.22 mass % or more, 0.23 mass % or more, 0.24 mass % or more, 0.25 mass % or more. There is no upper limit to the preferred Mn solid solution amount in the aluminum matrix phase, but under normal production conditions, the upper limit of the solid solution amount is 0.33 mass % or less.

[0091] The amount of Mn dissolved in the aluminum matrix phase is measured by using a cold-rolled aluminum alloy plate as a test material, removing the residue formed by the hot phenol dissolution extraction method, and taking the ratio of the amount of Mn contained in the obtained solution to the mass of the aluminum alloy plate dissolved by hot phenol as the amount of Mn dissolved. In other words, the Mn contained in the aluminum alloy includes Mn in a solid solution state and Mn in a state of an intermetallic compound as a second phase particle. The latter is separated by the hot phenol dissolution extraction method, and the amount of Mn analyzed from the solution extracted as the remaining matrix phase is divided by the mass of the aluminum alloy plate after dissolution to obtain the amount of Mn dissolved.

[0092] The hot phenol dissolution extraction method is described.

[0093] (1) Weigh 0.1 g of the test material and dissolve it in 25 mL of phenol.

[0094] (2) After dissolution, the extracted and filtered solution (X [mL]) is subjected to ICP emission spectrometry to measure the concentration of Mn in the solution (Y [g / mL]).

[0095] (3) Assuming that all the dissolved Mn in 0.1 [g] is contained in X [mL], the dissolved Mn concentration [mass %] of the sample is calculated by the following formula (I).

[0096] (solid solution Mn concentration [mass %]) = (Y [g / mL]) × (X [mL]) / (0.1 [g]) × 100 … (I)

[0097] In (2), after dissolution, the extracted and filtered solution was fixed to 50 mL. A portion of the fixed solution was used to perform quantitative analysis of Mn in the solution by ICP emission spectrometry. The obtained result was referred to as Y (g / mL).

[0098] In (3), the amount of Mn (solid solution) contained in 50 mL is calculated based on the analysis results obtained in (2). The solid solution Mn concentration (mass %) in the test sample is calculated from the above formula (I).

[0099] More specifically, it can be obtained by the method described in the examples.

[0100] <Young's modulus: 70GPa or more>

[0101] Young's modulus is the ratio of stress to strain when a material undergoes elastic behavior. In the present invention, it affects the vibration when a thin-walled magnetic disk is rotated by HDD. If the Young's modulus of the aluminum alloy plate is more than 70GPa, the vibration of the thin-walled magnetic disk can be reliably suppressed because of high rigidity. Therefore, the Young's modulus of the magnetic disk aluminum alloy plate of the present embodiment is preferably more than 70GPa. From the viewpoint of further suppressing the vibration of the thin-walled magnetic disk, the higher the Young's modulus, the more preferred. For example, the Young's modulus is preferably more than 71GPa, more preferably more than 72GPa, and more preferably more than 73GPa.

[0102] The Young's modulus can be adjusted by adjusting the contents of Mg, Si, Fe, Mn, and Ni to the contents described in this specification.

[0103] Young's modulus can be measured, for example, by making a 60 mm × 10 mm × 1 mm thick test piece with the rolling parallel direction as the longitudinal direction according to JIS Z 2280:1993 (Test method for high temperature Young's modulus of metal materials), and using the test piece. Specifically, it can be measured by a free resonance method at room temperature (e.g., 25° C.) in an atmospheric atmosphere according to the method specified in the JIS. The test apparatus is preferably a JE-RT model manufactured by Techno-Plus of Japan.

[0104] <Stress relaxation rate: 90% or less>

[0105] The present inventors have conducted intensive studies on deformation of a magnetic film of an aluminum alloy plate for a magnetic disk during sputtering, and have found that deformation can be suppressed by improving stress relaxation resistance.

[0106] If the stress relaxation rate is below 90%, even if the stress generated by the thermal strain during the sputtering of the magnetic film is applied to the substrate during the thinning process, deformation can be suppressed. Therefore, the stress relaxation rate of the aluminum alloy plate for magnetic disks of the present embodiment is preferably below 90%. From the viewpoint of further suppressing the deformation of the thin-walled substrate, the lower the stress relaxation rate, the more preferred. For example, the stress relaxation rate is more preferably below 85%, more preferably below 80%, and particularly preferably below 75%.

[0107] In addition, although the lower limit of the stress relaxation rate is not particularly limited, it is, for example, 0% or more, 20% or more, 50% or more, 60% or more, or 70% or more.

[0108] The stress relaxation rate can be adjusted by making the contents of Fe, Mn and Ni as described in this specification. In addition, in addition to the above-mentioned contents of Fe, Mn and Ni, it can also be adjusted by making the treatment conditions in the homogenization heat treatment process within the range described later and making the Mn solid solution amount in the aluminum matrix phase within the above-mentioned range.

[0109] The stress relaxation rate can be measured by the following test method.

[0110] A test piece of 10 mm wide and 60 mm long was cut so that the longitudinal direction was parallel to the rolling direction. Then, the following equations (2) and (3) were used to determine the bending stress in the following equation (1) so that it would be constant. Figure 1 The following test was performed for the span length (x) in (a).

[0111] In the state of loading bending stress ( Figure 1 (a) was placed in an atmospheric furnace and subjected to heat treatment (300°C x 1 hour) simulating the sputtering treatment of a magnetic film. Afterwards, it was taken out of the atmospheric furnace and the deformation a before the bending stress was unloaded was measured. Afterwards, the bending stress was released ( Figure 1 (b)), and measure the deformation b after the bending stress is unloaded.

[0112] The ratio of the deformation amount b after unloading the bending stress to the deformation amount a before unloading (b / a×100 [%]) was taken as the stress relaxation rate.

[0113] σ=M / Z …(1)

[0114] σ: Bending stress [N / mm 2 ]

[0115] M: Bending moment [N·mm]

[0116] Z: Section coefficient (Z [mm 3 ]=(w×t 2 ) / 6)

[0117] w: Plate width [mm], t: Plate thickness [mm]

[0118] M=P×x …(2)

[0119] M: Bending moment [N·mm]

[0120] P: Front load [N]

[0121] x: span length [mm]

[0122] P = (3 × E × I × δ) / x 3 … (3)

[0123] P: Front load [N]

[0124] E: Young's modulus [N / mm 2 ]

[0125] I: Second moment of area (I [mm 4 ]=(w×t 3 ) / 12)

[0126] w: Plate width [mm], t: Plate thickness [mm]

[0127] δ: Deflection (2 [mm])

[0128] x: span length [mm]

[0129] [Method for producing aluminum alloy plate for magnetic disk]

[0130] Next, an example of a method for producing the aluminum alloy plate for a magnetic disk according to the present embodiment will be described.

[0131] The aluminum alloy plate of the present embodiment can be manufactured by a manufacturing method and equipment under general conditions for manufacturing aluminum alloy plates for magnetic disks, except for some conditions in the homogenization heat treatment process and the hot rolling process. For example, the aluminum alloy plate can be manufactured by a manufacturing method that includes the following steps in order: a casting process, in which the raw material is melted, and the molten metal of the aluminum alloy adjusted to a specified chemical composition is cast into an aluminum alloy ingot by a semi-continuous casting method, etc.; a homogenization heat treatment process, in which the surface of the cast aluminum alloy ingot is cut and homogenized; a hot rolling process, in which the aluminum alloy ingot subjected to the homogenization heat treatment is hot-rolled to obtain a hot-rolled plate; a cold rolling process, in which the hot-rolled plate is cold-rolled. In addition, intermediate annealing can be performed before or during the cold rolling process as needed.

[0132] Hereinafter, each step will be described in detail.

[0133] (Casting process)

[0134] In the casting process, the raw material is melted at 700 to 800° C. to form a molten metal of the aluminum alloy. The molten metal is preferably cast at 700 to 800° C. into an aluminum alloy ingot by a known semi-continuous casting method such as a DC casting method.

[0135] (Homogenization heat treatment process)

[0136] In the homogenization heat treatment step, the cast aluminum alloy ingot is subjected to surface cutting and homogenization heat treatment. The surface cutting amount can be, for example, 2 to 40 mm / single side.

[0137] From the viewpoint of adjusting the stress relaxation rate of the aluminum alloy plate to 90% or less, the homogenization heat treatment is preferably performed at a temperature of 510 to 600°C at a heating rate of 15°C / h or more from room temperature to 510°C.

[0138] If the heating rate from room temperature to 510°C during homogenization heat treatment is lower than 15°C / h, the generation of intermetallic compounds containing Mn progresses during the heating process, the Mn solid solution content of the structure decreases, and sufficient stress relaxation resistance cannot be obtained. On the other hand, if the heating rate to 510°C is above 15°C / h, homogenization heat treatment can be performed before the generation of intermetallic compounds containing Mn, and the specified Mn solid solution content can be achieved. Therefore, the heating rate to 510°C is preferably above 15°C / h. More preferably, the heating rate to 510°C is above 18°C / h and above 20°C / h. There is no upper limit to the heating rate to 510°C during homogenization heat treatment, but if it is a normal manufacturing condition, it is below 100°C / h.

[0139] Moreover, by making the temperature of the homogenization heat treatment above 510°C, the homogenization of the structure and the solid solution of Mn are fully carried out, which can reduce the deviation of the stress relaxation resistance of the obtained aluminum alloy plate. In other words, after the homogenization heat treatment process, the Mn solid solution amount is sufficient, and the distribution is uniform, and there is no distribution difference in each part in the subsequent process. It is more preferred that the temperature of the homogenization heat treatment is above 515°C, and it is further preferred that it is above 520°C. On the other hand, by making the temperature of the homogenization heat treatment below 600°C, the surface of the aluminum alloy ingot can be prevented from melting. It is more preferred that the temperature of the homogenization heat treatment is below 580°C, and it is further preferred that it is below 540°C.

[0140] (Hot rolling process)

[0141] In the hot rolling step, the aluminum alloy ingot subjected to the homogenization heat treatment is hot rolled to obtain a hot rolled sheet.

[0142] From the viewpoint of adjusting the stress relaxation rate of the aluminum alloy sheet to 90% or less, the start temperature of hot rolling is preferably 480° C. or higher. In addition, the end temperature of hot rolling is preferably 300 to 350° C.

[0143] Specifically, by setting the starting temperature of hot rolling to 480°C or higher, the rolling load during hot rolling can be reduced, and the increase in the number of hot rolling passes can be suppressed. The starting temperature of hot rolling is more preferably 490°C or higher, and more preferably 500°C or higher. On the other hand, from the viewpoint of suppressing cracks during hot rolling, the starting temperature of hot rolling is preferably 550°C or lower, and more preferably 520°C or lower.

[0144] The thickness of the hot-rolled sheet obtained by hot rolling may be, for example, 3 mm or less.

[0145] (Cold rolling process)

[0146] In the cold rolling process, the obtained hot rolled sheet is cold rolled to obtain a cold rolled sheet. The thickness of the cold rolled sheet is, for example, preferably 0.3 to 1.3 mm, more preferably 0.70 mm or less, 0.69 mm or less, 0.65 mm or less, 0.60 mm or less, 0.55 mm or less, 0.50 mm or less, 0.45 mm or less, 0.40 mm or less, or 0.35 mm or less.

[0147] By sequentially going through these steps, the aluminum alloy plate of the present embodiment can be obtained.

[0148] [Aluminum alloy blank for magnetic disk]

[0149] The aluminum alloy blank for magnetic disks of the present embodiment is obtained from the aluminum alloy plate for magnetic disks. Specifically, the blank can be manufactured by sequentially performing the following steps: a punching step, in which the aluminum alloy plate obtained after the cold rolling step is punched into a ring shape; a corrective annealing step, in which a corrective annealing is performed on the ring-shaped substrate obtained by the punching step, such as by applying a load and annealing to flatten it.

[0150] The chemical composition of the obtained green body was the same as that of the above-mentioned aluminum alloy plate.

[0151] In addition, the various characteristic values ​​of Mn solid solution, Young's modulus, stress relaxation rate, etc. in the aluminum matrix of the blank are equivalent to the various characteristic values ​​of the aluminum alloy plate. Therefore, the characteristic values ​​required for the aluminum alloy plate can be regarded as the characteristic values ​​for the blank. In addition, the characteristic values ​​required for the blank can also be regarded as the characteristic values ​​for the aluminum alloy plate.

[0152] (Punching process)

[0153] In the punching process, the aluminum alloy plate can be tempered as needed and then punched into a circular shape so that it can be suitable for, for example, a substrate for a 3.5-inch HDD with an inner diameter of 24 mm and an outer diameter of 96 mm, or a substrate for a 2.5-inch HDD with an inner diameter of 19 mm and an outer diameter of 66 mm.

[0154] (Corrective annealing process)

[0155] In the correction annealing step, it is preferred to sandwich the annular substrates with spacers having high flatness and stack them, and anneal them while applying a load to the substrates to flatten them. The annealing temperature is 250 to 500° C., and the holding time can be, for example, about 3 to 5 hours.

[0156] The heating rate of the correction annealing can be, for example, about 80° C. / hour on average, preferably 1000° C. / hour at the fastest. The temperature can be lowered (cooled) by, for example, opening the door of the annealing furnace.

[0157] Regarding the temperature rise of the corrective annealing, even if the temperature rise is carried out in stages, the effect of the present embodiment will not be impaired. For example, as described in paragraphs 0068 and 0069 of Japanese Patent Gazette No. 5815153, the temperature rise rate in a specific temperature range can be set to a predetermined rate or higher, and the temperature rise rates outside the specific temperature range can be set to different rates, so that the temperature rise is carried out at a plurality of temperature rise rates, that is, the temperature rise is carried out in stages.

[0158] In the present embodiment, the annealing temperature of the correction annealing is set within the above-mentioned normal annealing temperature range, and 250 to 400° C. is also set as a practical temperature region.

[0159] By sequentially going through these steps, the green body of this embodiment can be obtained.

[0160] [Aluminum alloy substrate for magnetic disk]

[0161] The aluminum alloy substrate for magnetic disk of the present embodiment is obtained from the aluminum alloy blank for magnetic disk described above. Specifically, the substrate can be manufactured by cutting the blank end face (end face processing) and grinding the blank surface (main surface) (mirror finishing).

[0162] The chemical composition of the obtained substrate is the same as that of the above-mentioned green body.

[0163] In addition, the various characteristic values ​​such as the Mn solid solution content, Young's modulus, and stress relaxation rate in the aluminum matrix of the substrate are equivalent to the various characteristic values ​​of the blank. Therefore, the characteristic values ​​required for the aluminum alloy plate and the blank can be regarded as the characteristic values ​​for the substrate. In addition, the characteristic values ​​required for the substrate can also be regarded as the characteristic values ​​for the aluminum alloy plate and the blank.

[0164] The aluminum alloy plate, blank, and substrate of the present embodiment can be obtained by the above-mentioned methods respectively, but may also undergo other steps between or before and after the steps as long as they do not have an adverse effect on the steps.

[0165] [Method of manufacturing magnetic disk]

[0166] The magnetic disk can be manufactured by a manufacturing method and equipment under general conditions for manufacturing magnetic disks. For example, after the surface of the substrate is subjected to acid etching to form an electroless Ni-P plated film, the surface of the electroless Ni-P plated film is polished. Then, a base layer, a magnetic layer, a protective film, etc. are formed on the surface of the substrate, thereby manufacturing the magnetic disk.

[0167] Example

[0168] Hereinafter, the present invention will be described in more detail with reference to the embodiments of the present invention, but the technical scope of the present invention is not limited thereto.

[0169] (Preparation of test materials)

[0170] The test materials No. 1 to 3 were produced using aluminum alloys having the chemical compositions shown in Table 1 under the following conditions.

[0171] First, for the molten metal, a slab is made by DC casting using a mold with an ingot thickness (No. 1 and 2 are 500 mm, and No. 3 is 535 mm). Then, 16 mm surface cutting is performed on both sides (thickness direction) of the obtained slab. After that, a homogenization heat treatment is performed at the heating rate described in Table 1, from room temperature (25°C) to 510°C, and maintained at 535°C for 8 hours. Then, hot rolling is performed, No. 1 and 3 are rolled to a thickness of 2.3 mm, and No. 2 is rolled to a thickness of 2.0 mm (starting temperature: about 500°C, ending temperature: about 330°C), and cold rolling is performed, No. 1 is rolled to a thickness of 0.55 mm, and No. 2 and 3 are rolled to a thickness of 0.52 mm, to obtain aluminum alloy plates of various plate thicknesses. After that, the steel is punched at about 98φ using a punching machine and subjected to correction annealing (heating at 200 to 280°C at a heating rate of 50°C / h or more and then maintaining at 300 to 400°C for 7 hours) by clamping with a partition plate to produce blanks (O-type tempered materials) of various plate thicknesses.

[0172] For each of the produced test pieces, the Mn solid solution content in the aluminum matrix phase, the Young's modulus, and the stress relaxation rate were evaluated as follows.

[0173] (Mn solid solution content in aluminum matrix)

[0174] The amount of Mn dissolved in the aluminum matrix is ​​measured by using a blank after correction annealing as a test material, removing the residue by hot phenol dissolution extraction, and taking the ratio of the amount of Mn contained in the obtained solution to the mass of the blank dissolved by hot phenol as the amount of Mn dissolved. In other words, the Mn contained in the aluminum alloy includes Mn in a solid solution state and Mn in a state of an intermetallic compound as a second phase particle. The latter is separated by hot phenol dissolution extraction, and the amount of Mn analyzed from the solution extracted as the remaining matrix is ​​divided by the mass of the aluminum alloy plate after dissolution to obtain the amount of Mn dissolved.

[0175] The test piece is a small piece cut from the blank after the correction annealing, and weighed to make a total of 0.1g. Next, a beaker with 25mL of phenol is placed on a hot plate, and after the phenol is heated at a set temperature of 250°C, the test piece is put in to dissolve it. Next, benzyl alcohol is added to the above solution. Next, the liquid with benzyl alcohol added is filtered with a polytetrafluoroethylene membrane filter (pore size 0.1μm) to remove the second phase particles as residue. The solution after removing the second phase particles is quantitatively analyzed by inductively coupled plasma emission spectrometry (ICP). Thus, the Mn solid solution amount is obtained by dividing the value of the obtained Mn amount by the mass of the dissolved blank 0.1g.

[0176] (Young's modulus)

[0177] The Young's modulus is measured in accordance with JIS Z 2280:1993 (Method for testing Young's modulus of metal materials at high temperatures). A test piece of 60 mm × 10 mm × thickness of the test piece (mm) with the rolling parallel direction as the longitudinal direction is cut from the test piece (blank), and the test piece is used for measurement. The thickness of the test piece is 0.55 mm for No. 1 and 0.52 mm for No. 2 and 3.

[0178] The measurement was performed using a JE-RT test device manufactured by Japan Techno-Plus Co., Ltd. in an air atmosphere at room temperature (25° C.) by a free resonance method.

[0179] The Young's modulus of 70 GPa or more was evaluated as "○", and the Young's modulus of less than 70 GPa was evaluated as "×". ○ means pass, and × means fail.

[0180] (Stress relaxation rate)

[0181] A test piece of 10 mm wide x 60 mm long was cut from the test material (blank) in such a way that the longitudinal direction was parallel to the rolling direction. Then, the bending stress in the following formula (1) was constant, and the following formulas (2) and (3) were used to determine the bending stress for each test material. Figure 1 (a) and perform the following test.

[0182] In the state of loading bending stress ( Figure 1 (a) was placed in an atmospheric furnace and subjected to heat treatment (300°C x 1 hour) simulating the sputtering treatment of a magnetic film. Afterwards, it was taken out of the atmospheric furnace and the deformation a before the bending stress was unloaded was measured. Afterwards, the bending stress was released ( Figure 1 (b)), and measure the deformation b after the bending stress is unloaded.

[0183] The ratio of the deformation amount b after unloading of the bending stress to the deformation amount a before unloading (b / a×100[%]) was taken as the stress relaxation rate. A stress relaxation rate of 90% or less was evaluated as excellent deformation suppression during sputtering of the magnetic film "0", and a stress relaxation rate of more than 90% was evaluated as poor deformation suppression during sputtering of the magnetic film "×".

[0184] σ=M / Z …(1)

[0185] σ: Bending stress [N / mm 2 ]

[0186] M: Bending moment [N·mm]

[0187] Z: Section coefficient (Z [mm 3 ]=(w×t 2 ) / 6)

[0188] w: Plate width [mm], t: Plate thickness [mm]

[0189] M=P×x …(2)

[0190] M: Bending moment [N·mm]

[0191] P: Front load [N]

[0192] x: span length [mm]

[0193] P = (3 × E × I × δ) / x 3 … (3)

[0194] P: Front load [N]

[0195] E: Young's modulus [N / mm 2 ]

[0196] I: Second moment of area (I [mm 4 ]=(w×t 3 ) / 12)

[0197] w: Plate width [mm], t: Plate thickness [mm]

[0198] δ: Deflection (2 [mm])

[0199] x: span length [mm]

[0200] Table 1 shows the alloy composition (chemical composition), Young's modulus, and stress relaxation rate evaluation results of each test material (blank), and the measurement results of the Mn solid solution amount in the aluminum matrix of each test material (blank). In addition, the underlined items in the table indicate that the invention-specific matters of the present invention are not satisfied.

[0201]

Table 1

[0202]

[0203] The results in Table 1 show that No. 1 and No. 2 satisfying the requirements of the present invention have good rigidity and excellent stress relaxation resistance, and can provide aluminum alloy plates and blanks capable of suppressing thermal deformation during magnetic film sputtering.

[0204] On the other hand, No. 3, in which the total amount of Fe, Mn and Ni does not satisfy the requirements of the present invention and the amount of Mn dissolved in the aluminum matrix does not satisfy the requirements of the present invention, is inferior to Nos. 1 and 2 in rigidity and stress relaxation resistance.

Claims

1. An aluminum alloy plate for a magnetic disk, comprising: Mg: 0.1 to 7.0 mass %, Cr: 0.005 to 1.0 mass %, Be: 3 to 100 mass ppm, and Mn, and Ti: 100 mass ppm or less, Si: 0.20 mass % or less, Total of Fe, at least one of Mn and Ni: 0.03-5.9 mass % The balance contains Al and impurities, The amount of Mn dissolved in the aluminum matrix phase is 0.03 mass % or more.

2. The aluminum alloy plate for magnetic disk according to claim 1, wherein The alloy contains at least one of 0 to 1.00 mass % of Fe, 0.03 to 1.4 mass % of Mn, and 0 to 3.5 mass % of Ni.

3. The aluminum alloy plate for magnetic disk according to claim 1 or 2, wherein: It further contains at least one of Cu: 1.0 mass % or less and Zn: 1.0 mass % or less.

4. The aluminum alloy plate for magnetic disk according to claim 1 or 2, wherein The Young's modulus is 70 GPa or more.

5. The aluminum alloy plate for magnetic disk according to claim 1 or 2, wherein The stress relaxation rate is less than 90%. 6 . An aluminum alloy blank for a magnetic disk, obtained from the aluminum alloy sheet for a magnetic disk according to claim 1 .

7. An aluminum alloy substrate for a magnetic disk, which is obtained from the aluminum alloy blank for a magnetic disk according to claim 6.

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