JP2020114944A - Aluminum alloy sheet for magnetic disk, aluminum alloy blank for magnetic disk, and aluminum alloy substrate for magnetic disk - Google Patents

Abstract

To provide an aluminum alloy sheet for a magnetic disk, an aluminum alloy blank for a magnetic disk, and an aluminum alloy substrate for a magnetic disk, having excellent rigidity and excellent smoothness of an electroless Ni-P plating film formed on the surface.SOLUTION: An Al alloy sheet for a magnetic disk according to the present invention contains: Mg: 3.00 mass% or less and Si: 1.00 mass% or less; it contains at least one of Fe: 5.0 mass% or less, Mn: 5.0 mass% or less, and Ni: 5.0 mass% or less, the total amount thereof being 8.0 mass% or less; and it contains at least one of Cr: 2.0 mass% or less, Ti: 0.5 mass% or less, and Zr: 2.0 mass% or less, the total amount thereof being 2.0 mass% or less; the balance consists of Al and unavoidable impurities; in the unavoidable impurities, individual amounts of V, B, Na, K, Ca, and Sr being 0.005% or less, and the total amount thereof 0.015% or less; the area ratio of the surface occupied by intermetallic compounds is 5-40%; and the total area ratio of simple Si and Mg-Si intermetallic compound is 1% or less.SELECTED DRAWING: None

Description

The present invention relates to an aluminum alloy plate for magnetic disks, an aluminum alloy blank for magnetic disks, and an aluminum alloy substrate for magnetic disks.

A magnetic disk made of an aluminum (Al) alloy is used as a recording medium such as a computer and a hard disk drive (HDD). In such a magnetic disk, after the surface of the plate material is mirror-finished, degreasing treatment, acid etching treatment, desmut treatment, 1st zincate treatment, nitric acid peeling treatment, 2nd zincate treatment, and electroless Ni-P plating treatment are performed in this order. It is manufactured by forming a magnetic film, a protective film, and the like.

Due to the demand for larger recording capacity, there is a demand (needs) to increase the number of magnetic disks mounted inside. In order to meet the needs, thinning of the magnetic disk has been studied, but if the magnetic disk is made thin, there is a problem that vibration generated when the magnetic disk is rotated by the HDD tends to be large. On the other hand, the glass substrate is originally high in rigidity, but there is a problem that the production cost (grinding) for flattening is inferior. In order to solve such a problem, there is a need to increase the rigidity of a magnetic disk blank that uses an aluminum rolled plate that is excellent in production cost.

For example, Patent Document 1 discloses an invention relating to a magnetic disk intended for high rigidity. The invention described in Patent Document 1 is to disperse at least one of ceramic particles or ceramic fibers in an Al alloy matrix in a volume ratio of 5 to 50%.
Note that Patent Document 1 describes that an Al alloy plate used for the magnetic disk is manufactured as follows. That is, pure Al particles obtained by the atomizing method as matrix particles and Al ₂ O ₃ particles as reinforcing fibers are prepared, and these are uniformly mixed (fiber volume ratio 15%). It is described that the mixture is put into a mold and HIP (Hot Isostatic Pressing) treatment is performed near the melting temperature, followed by hot rolling to produce a plate having a predetermined plate thickness. Note that this method requires processing one by one, and thus has the same problem as the glass substrate that the production cost is inferior.

JP-A-63-183146

As described above, since the invention described in Patent Document 1 is obtained by mixing matrix particles and reinforcing fibers and performing HIP treatment near the melting temperature, the adhesion between the matrix particles and the reinforcing fibers. May not be enough. Therefore, in the Al alloy plate described in Patent Document 1, there is a possibility that the smoothness of the electroless Ni-P plating film formed on the plate surface cannot be made high enough to satisfy the recent recording density.
Further, as described above, there is a need to increase the rigidity of the magnetic disk blank to which the rolled aluminum plate, which is excellent in production cost, is applied.

The present invention has been made in view of the above circumstances, and has excellent rigidity (for example, Young's modulus) and smoothness of an electroless Ni-P plating film formed on a surface thereof, an aluminum alloy plate for a magnetic disk, and a magnetic disk An object is to provide an aluminum alloy blank and an aluminum alloy substrate for a magnetic disk.

As a result of intensive studies to solve the above problems, the present inventor has found that the rigidity of the entire substrate can be improved by increasing the area ratio of the intermetallic compound. In addition, the present inventors have found that intermetallic compounds such as simple Si and Mg-Si based intermetallic compounds do not have electroless Ni-P plating deposited on the surface, and intermetallic compounds other than these. As described above, it was found that the electroless Ni-P plating is deposited on the surface. The present inventor has found that the electroless Ni-P plating can selectively increase the area ratio of the intermetallic compound deposited on the surface to enhance the rigidity and simultaneously suppress the occurrence of plating defects. Has been completed.

The aluminum alloy plate for a magnetic disk according to the present invention which has solved the above-mentioned problems is Mg: 3.00 mass% or less, Si: 1.00 mass% or less, Fe: 5.0 mass% or less, Mn: 5. At least one of 0 mass% or less and Ni: 5.0 mass% or less is contained, and the total amount thereof is 8.0 mass% or less, Cr: 2.0 mass% or less, Ti: 0.5 % Or less, Zr: 2.0% by weight or less, and the total amount is 2.0% by weight or less, the balance is Al and inevitable impurities, Among them, V, B, Na, K, Ca, and Sr are individually 0.005 mass% or less and 0.015 mass% or less in total, and the area ratio of the intermetallic compound on the surface is 5 to 40% and The total area ratio of the simple substance Si and the Mg-Si based intermetallic compound is determined to be 1% or less.
Further, the aluminum alloy plate for a magnetic disk according to the present invention is Mg: 3.00 mass% or less, Si: 0.20 mass% or less, Fe: 5.0 mass% or less, Mn: 5.0 mass%. Hereinafter, at least one of Ni: 5.0 mass% or less is contained, and the total amount thereof is 8.0 mass% or less, Cr: 2.0 mass% or less, Ti: 0.5 mass% or less. , Zr: at least one of 2.0 mass% or less, the total amount thereof is 2.0 mass% or less, the balance being Al and inevitable impurities, and the area of the intermetallic compound occupying the surface. The ratio is 5 to 40%, and the total area ratio of elemental Si and Mg-Si intermetallic compounds is 1% or less.

As described above, the aluminum alloy plate for a magnetic disk according to the present invention contains Mg in a predetermined value or less, contains Fe, Mn, Ni, and Cr, Ti, Zr in predetermined amounts, and occupies the surface of the metal. Since the area ratio of the intercalation compound is within a predetermined range, it has excellent rigidity. Further, the aluminum alloy plate for a magnetic disk according to the present invention has a total area ratio of elemental Si and Mg—Si based intermetallic compounds occupying on the surface not more than a predetermined value, so that electroless Ni—P plating formed on the surface is performed. The number of pits formed in the film can be further reduced, and the plated film can have excellent smoothness. Further, among the unavoidable impurities, when V, B, Na, K, Ca, and Sr are individually set to be not more than a predetermined value and not more than a predetermined value in total, as long as these conditions are satisfied, they are regarded as unavoidable impurities. The effect of the present invention is not impaired even if these are contained.

In the aluminum alloy plate for a magnetic disk according to the present invention, the total amount of Fe, Mn and Ni is preferably 0.7% by mass or more and 8.0% by mass or less.
As described above, since the aluminum alloy plate for a magnetic disk according to the present invention has the total amount of Fe, Mn, and Ni within a predetermined range, it is possible to secure Young's modulus and prevent hot cracking.
In the aluminum alloy plate for a magnetic disk according to the present invention, the total amount of Cr, Ti, and Zr is preferably 0.1% by mass or more and 2.0% by mass or less.
As described above, since the aluminum alloy plate for a magnetic disk according to the present invention has the total amount of Cr, Ti, and Zr within the predetermined range, it is possible to further suppress the generation of megacrystals and prevent hot cracking.

The Young's modulus of the aluminum alloy plate for a magnetic disk according to the present invention is preferably 73 GPa or more.
As described above, the aluminum alloy plate for a magnetic disk according to the present invention has a Young's modulus of not less than a predetermined value, and thus can have excellent rigidity.

The aluminum alloy plate for a magnetic disk according to the present invention preferably has an absolute maximum length of the intermetallic compound on the surface of 50 μm or less.

As described above, since the aluminum alloy plate for a magnetic disk according to the present invention has the absolute maximum length of the intermetallic compound on the surface not more than a predetermined value, the smoothness of the electroless Ni-P plated film formed on the surface is further improved. It can be excellent.

The aluminum alloy plate for a magnetic disk according to the present invention contains at least one of Cu: 0.1% by mass or more and 10.0% by mass or less and Zn: 0.1% by mass or more and 10.0% by mass or less. Is preferred.

As described above, the aluminum alloy plate for a magnetic disk according to the present invention contains Cu and Zn at a predetermined value or less, so that the surface of the electroless Ni-P plated film formed on the surface of the blank (substrate) is smoothed. The property can be further improved.

The aluminum alloy blank for a magnetic disk according to the present invention uses the aluminum alloy plate for a magnetic disk described in any one of the above.
As described above, since the aluminum alloy blank for a magnetic disk according to the present invention uses the aluminum alloy plate for a magnetic disk according to the present invention described above, the rigidity and the smoothness of the electroless Ni-P plating film formed on the surface of the aluminum alloy blank for a magnetic disk are used. It can be made to have excellent properties.
The yield strength of the aluminum alloy blank for a magnetic disk according to the present invention is preferably 90 MPa or more.
As described above, the aluminum alloy blank for a magnetic disk according to the present invention has a proof stress of a predetermined value or more, and therefore, strength enough to maintain the impact resistance required as a magnetic disk can be obtained.

The aluminum alloy substrate for a magnetic disk according to the present invention uses the aluminum alloy blank for a magnetic disk according to the present invention.
As described above, since the aluminum alloy substrate for a magnetic disk according to the present invention uses the aluminum alloy blank for a magnetic disk according to the present invention, the rigidity and the electroless Ni-P plating film formed on the surface of the aluminum alloy substrate for a magnetic disk are used. It can be made to have excellent smoothness.

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 invention have excellent rigidity and smoothness of the electroless Ni-P plated film formed on the surface.

Hereinafter, modes for carrying out an aluminum alloy blank for a magnetic disk and an aluminum alloy substrate for a magnetic disk (hereinafter, may be simply referred to as “blank” and “substrate”, respectively) according to the present invention will be described in detail. To do.

[First embodiment of blank]
First, the first embodiment of the blank will be described.
The blank according to the present embodiment has Mg: 3.00 mass% or less and Si: 1.00 mass% or less. Further, the blank according to the present embodiment contains at least one of Fe: 5.0 mass% or less, Mn: 5.0 mass% or less, and Ni: 5.0 mass% or less, and the total amount thereof is It is set to 8.0 mass% or less. Further, the blank according to the present embodiment contains at least one of Cr: 2.0 mass% or less, Ti: 0.5 mass% or less, and Zr: 2.0 mass% or less, and the total amount thereof is It is set to 2.0% by mass or less. The rest of the chemical composition of the blank according to the present embodiment is formed in a predetermined shape using an aluminum alloy containing Al and unavoidable impurities.
The blank according to the present embodiment is configured such that the area ratio of the intermetallic compound occupying the surface is 5 to 40% and the total area ratio of the simple Si and Mg-Si based intermetallic compounds is 1% or less.

(Mg)
When Mg is contained alone, the yield strength of the blank can be improved. However, since Young's modulus decreases as Mg increases, it becomes difficult to set the Young's modulus to 73 GPa or more when Mg exceeds 3.00 mass %. Therefore, Mg is 3.00 mass% or less. From the viewpoint of maintaining a high Young's modulus of the blank, Mg is preferably 2.00 mass% or less, and more preferably 1.00 mass% or less.
Further, since Mg is bonded to Si as described later to increase the amount of Mg-Si-based intermetallic compound produced, from the viewpoint of suppressing this, it is 3.00% by mass or less as described above. From the viewpoint of suppressing the Mg-Si intermetallic compound, the lower the amount of Mg is, the more preferable it is. However, in order to suppress the lower limit of Mg, it is necessary to use a high-purity raw material with a low amount of Mg, which increases the cost. In the present invention, if the Mg content can be suppressed to about 0.005 mass %, the formation of the Mg—Si based intermetallic compound can be sufficiently suppressed. Therefore, when the lower limit of the Mg content is set, it is 0.005 mass %. Is preferred.

(Si)
Si is usually mixed in the Al alloy as a metal ingot impurity, and in the step of casting the ingot of the Al alloy, Si and Mg-Si-based intermetallic compounds are added to the ingot and the plate surface of the Al alloy. Give rise to.
When Si exceeds 1.00 mass %, the production amount of elemental Si and Mg—Si based intermetallic compound increases. If the amount of the simple substance Si and the Mg—Si intermetallic compound produced is too large, the proof stress of a level required as a blank may not be maintained. Moreover, since the electroless Ni-P plating film is not coated on the simple substance Si and the Mg-Si intermetallic compound, the smoothness after forming the electroless Ni-P plating film is poor. Therefore, Si is 1.00 mass% or less. The smaller the amount of Si, the more preferable, and it is preferably 0.20% by mass or less, more preferably 0.10% by mass or less. In addition, in order to set Si to less than 0.005 mass %, it is necessary to use a high-purity metal ingot, which is very high cost, which is not realistic. Therefore, when setting the lower limit of the amount of Si, it is preferable to set it to 0.005 mass %.

(Fe, Mn, Ni)
In the present invention, the Young's modulus of the blank is improved by containing at least one of Fe, Mn and Ni. However, if at least one of Fe, Mn, and Ni alone exceeds 5.0% by mass, or if the total of two or more kinds exceeds 8.0% by mass, rolling cannot be performed. That is, the intermetallic compound increases excessively, the ductility decreases, and cracks (hereinafter sometimes simply referred to as “hot cracking”) occur in the hot rolled sheet during hot rolling. Therefore, at least one of Fe: 5.0 mass% or less, Mn: 5.0 mass% or less, and Ni: 5.0 mass% or less is contained, and the total amount thereof is 8.0 mass% or less. ..
If Fe, Mn, and Ni are excessively added, coarse crystals are likely to occur. Coarse crystals may become plating defects if they fall off in the pretreatment step of plating, so from the viewpoint of plating smoothness, Fe is 2.0 mass% or less, Mn is 2.0 mass% or less, and Ni is It is preferably 2.0% by mass or less, and the total amount thereof is preferably 4.0% by mass or less. On the other hand, from the viewpoint of ensuring the Young's modulus, the total amount of Fe, Mn, and Ni is preferably 0.7% by mass or more.

(Cr, Ti, Zr)
In the present invention, by containing at least one of Cr, Ti, and Zr, generation of megacrystals is suppressed, and the electroless Ni-P plated film formed on the surface of the blank (substrate) is excellent. Will be things. However, if Cr exceeds 2.0% by mass, Ti exceeds 0.5% by mass, Zr exceeds 2.0% by mass, or the total amount thereof exceeds 2.0% by mass, heat Cracking occurs. Therefore, at least one of Cr: 2.0 mass% or less, Ti: 0.5 mass% or less, and Zr: 2.0 mass% or less is contained, and the total amount thereof is 2.0 mass% or less. ..
If Cr, Ti, and Zr are excessively added, coarse crystals are likely to occur. Coarse crystals may become plating defects if they fall off in the pretreatment step of plating. Therefore, from the viewpoint of plating smoothness, the total amount of Cr, Ti, and Zr is preferably 0.3% by mass or less. .. From the viewpoint of further suppressing generation of megacrystals, the total amount of Cr, Ti, and Zr is preferably 0.1% by mass or more, and more preferably 0.2% by mass or more.

(The rest)
The basic components of the chemical composition constituting the blank according to the present invention are as described above, and the remaining components are Al and inevitable impurities (unavoidable impurities other than Si described above). The unavoidable impurities are impurities that are inevitably mixed in when the material is dissolved, and are contained in a range that does not impair various characteristics of the blank. Examples of such unavoidable impurities include V, B, Na, K, Ca, and Sr. If the unavoidable impurities are 0.005% by mass or less individually and 0.015% by mass or less in total, the effect of the present invention is not impaired. Therefore, in the present invention, an unavoidable impurity may be contained in a range that does not impair the effects of the present invention, and an element other than the elements described in the present specification may be included in a range that does not impair the effects of the present invention. May be positively contained (that is, these embodiments are also included in the technical scope of the present invention). Further, in the present embodiment, Cu and Zn may be contained as the remaining components in an amount of less than 0.1% by mass.

The chemical composition of the blank according to the present invention can be adjusted appropriately, for example, by the amount of the element added when melting the Al alloy. Further, the adjustment (regulation) of the content of unavoidable impurities can be performed, for example, by using a metal refined by a three-layer electrolysis method or by using a segregation method to eliminate them.

(Area ratio of intermetallic compounds on the surface)
As the intermetallic compound occupying the surface, for example, Mg-Si based intermetallic compound, Al-Fe based intermetallic compound, Al-Mn based intermetallic compound, Al-Ni based intermetallic compound, Al-Fe-Mn based metal. Intermetallic compound, Al-Fe-Ni-based intermetallic compound, Al-Mn-Ni-based intermetallic compound, Al-Fe-Mn-Ni-based intermetallic compound, Al-Cr-based intermetallic compound, Al-Ti-based intermetallic compound , Al-Zr-based intermetallic compounds, and the like. Further, in this case, an Al-Fe-Cr intermetallic compound in which a part of the Al-Fe intermetallic compound is replaced, or an Al-Mn-Cr system in which a part of the Al-Mn intermetallic compound is replaced. Intermetallic compounds are also applicable. Further, as will be described later, when Cu and Zn are contained in the amounts specified in the present invention, an Al-Cu-based intermetallic compound, an Al-Zn-based intermetallic compound and the like can be mentioned. In the present invention, simple substance Si is also treated as an intermetallic compound.

By setting the area ratio of the above-mentioned intermetallic compound on the surface to 5% or more, the Young's modulus of the blank can be 73 GPa or more. On the other hand, when the area ratio is less than 5%, the Young's modulus of the blank cannot be 73 GPa or more. If the area ratio exceeds 40%, hot cracking or surface defects may occur. Therefore, in the present invention, the area ratio is set to 5 to 40%. From the viewpoint of further increasing the Young's modulus of the blank, the area ratio is preferably 10% or more, and more preferably 15% or more. Further, from the viewpoint of obtaining a more excellent surface texture, the area ratio is preferably 38% or less, more preferably 35% or less.

The area ratio can be adjusted by adjusting the contents of Si, Mg, Fe, Mn, Ni, Cr, Ti, and Zr described in the present specification, and when Cu and Zn are contained, these are specified in the present specification. The content can be adjusted by adjusting the content described in (Note that Cu and Zn will be described later).

(Total area ratio of elemental Si and Mg-Si intermetallic compounds on the surface)
Of the above-mentioned intermetallic compounds, the elemental Si and Mg-Si based intermetallic compounds are not coated with the electroless Ni-P plating film as described above. Therefore, if the total area ratio of the elemental Si and the Mg—Si intermetallic compound on the surface is large, many pits are formed in the electroless Ni—P plating film formed on the surface of the blank (substrate), and the electroless Ni—P plating film is formed. The smoothness after forming the Ni-P plated film is poor. Moreover, when there are many simple substance Si and Mg-Si type|system|group intermetallic compounds, it becomes difficult to make the yield strength of the aluminum alloy for magnetic discs 90 MPa or more. Therefore, in the present invention, the total area ratio of elemental Si and Mg—Si based intermetallic compounds on the surface is set to 1.0% or less. The smaller the total of these area ratios, the more preferable. For example, it is preferably 0.9% or less or less than 0.1%.
The total area ratio of the simple substance Si and the Mg-Si based intermetallic compound can be controlled by adjusting the Si content to the above-mentioned content or less.

The area ratio of each of the above-mentioned intermetallic compounds (including elemental Si) on the surface can be obtained as follows. For example, an FE-SEM (Field Emission Scanning Electron Microscope, model JSM-7001F) manufactured by JEOL Ltd. is used and the acceleration voltage is set to 15 kV. Then, using the attached analysis system “Analysis Station 3,8,0,31” and particle analysis software “EX-35110 particle analysis software Ver. The area ratio of Si, Mg-Si based intermetallic compound, Al-Fe based intermetallic compound, etc. can be calculated.

(Young's modulus)
The Young's modulus is the ratio of stress and strain when the material behaves elastically, and in the present invention, it affects the generation of vibration when the thinned magnetic disk is rotated by the HDD. When the Young's modulus is 73 GPa or more, the rigidity is high, so that the vibration of the thinned magnetic disk can be reliably suppressed. Therefore, in the present invention, the Young's modulus is preferably 73 GPa or more. From the viewpoint of further suppressing the vibration of the thinned magnetic disk, the higher Young's modulus is more preferable. For example, the Young's modulus is preferably 75 GPa or more, more preferably 80 GPa or more, further preferably 83 GPa or more, and even more preferably 85 GPa or more. The Young's modulus of 80 GPa corresponds to a glass substrate.
The Young's modulus can be adjusted by setting Mg, Fe, Mn, Ni, Cr, Ti, and Zr to the contents described in the present specification, and by setting the area ratio of the intermetallic compound on the surface to a predetermined range.
The Young's modulus is, for example, in accordance with JIS Z 2280:1993 (high temperature Young's modulus test method for metal materials), a 60 mm×10 mm×1 mm thick test piece having a longitudinal direction parallel to the rolling direction is prepared, and the test piece is prepared. Can be measured by using. Specifically, it can be measured by a free resonance method at room temperature in the atmosphere according to the method specified in JIS. As the test device, it is preferable to use JE-RT type manufactured by Nippon Techno Plus Co., Ltd.

(Proof strength)
The yield strength is preferably 90 MPa or more in order to obtain sufficient strength as a blank (and further as a substrate and a magnetic disk). If the proof stress is less than 90 MPa, sufficient strength as a blank cannot be obtained. From the viewpoint of obtaining higher strength as a blank, the yield strength is preferably 100 MPa or more, more preferably 110 MPa or more, even more preferably 120 MPa or more, even more preferably 130 MPa or more.
The proof stress is obtained by adding the addition amount of Fe, Mn, Ni, Mg or the like within the above predetermined amount and adjusting the annealing condition to control the production amount of each intermetallic compound and the solid solution amount in the matrix. Can be adjusted.
The proof stress is obtained, for example, according to JIS Z 2241:2011 (Metallic material tensile test method) and by making a JIS 5 test piece having the rolling parallel direction as the longitudinal direction and conducting a metallic material tensile test. When it is difficult to manufacture the test piece from a blank or a substrate, for example, a part of the cold rolled plate in the process of manufacture is cut out and annealed at 320° C. for 3 hours, which is equivalent to straightening annealing. After that, according to JIS Z 2241:2011 (Metallic material tensile test method), a JIS No. 5 test piece having a rolling parallel direction as a longitudinal direction is prepared and a metallic material tensile test is performed. It should be noted that the same value is obtained when a test piece is manufactured by reducing a blank to a dimension ratio similar to the JIS No. 5 test piece and measuring the same.

(Absolute maximum length of intermetallic compound on the surface)
The absolute maximum length of the intermetallic compound on the surface is preferably 50 μm or less. By doing so, the electroless Ni-P plated film can be formed favorably, so that the thickness of the plated film can be reduced. Moreover, since the intermetallic compound is fine, the yield strength is improved. The "absolute maximum length" means, for example, the distance between the two points that are most distant from each other on the corresponding particle recognized when observed in a COMPO image of SEM or the like. The smaller the absolute maximum length of the intermetallic compound, the lower the risk of plating defects due to the loss of coarse crystals. From such a viewpoint, the absolute maximum length of the intermetallic compound is more preferably 30 μm or less, further preferably 25 μm or less, and further preferably 20 μm or less.
The absolute maximum length of the intermetallic compound can be adjusted by adjusting the content of Si, Mg, Fe, Mn, Ni, Cr, Ti, Zr and the like described in the present specification.

[Blank second embodiment]
Next, a second embodiment of the blank will be described.
The blank according to the second embodiment is obtained by adding various elements to the above chemical composition in order to further improve various characteristics.
(Cu, Zn)
The blank according to the second embodiment has the chemical composition of the blank according to the first embodiment with Cu: 0.1% by mass or more and 10.0% by mass or less, Zn: 0.1% by mass or more and 10.0% by mass or less. Of these, at least one is contained.
Cu and Zn are uniformly solid-dissolved in the blank (substrate), and in the zincate treatment before plating, Zn ions in the zincate bath are uniformly and finely deposited on the surface of the blank (substrate). Therefore, the number of pits formed in the electroless Ni-P plated film of the blank (substrate) is further reduced, and the smoothness of the plated film is further improved. In order to obtain such an effect, as described above, Cu contains at least one of 0.1 mass% or more and 10.0 mass% or less and Zn contains 0.1 mass% or more and 10.0 mass% or less. I have decided. If the Cu content and the Zn content exceed 10.0% by mass, the amount of the intermetallic compound produced increases, which may cause hot cracking.

In addition, the chemical composition of the blank according to the second embodiment, the area ratio of the intermetallic compound occupying the surface, the Young's modulus, the yield strength, and the total area ratio of the simple Si and Mg-Si intermetallic compounds occupying the surface are the first The description is omitted because it is the same as the embodiment.

The blanks according to the first embodiment and the second embodiment described above have a chemical composition, an area ratio of intermetallic compounds occupying the surface, and an area ratio of elemental Si and Mg-Si based intermetallic compounds occupying the surface. The total and are specified as described above. Therefore, the blanks according to the first embodiment and the second embodiment are both excellent in rigidity and smoothness of the electroless Ni-P plating film formed on the surface.

[substrate]
The substrate according to the present embodiment uses the blank according to the first embodiment or the second embodiment described above. Specifically, the substrate according to the present embodiment is manufactured by smoothing (grinding, mirror-finishing) the surface of the blank described above.
Here, the substrate according to the present embodiment has the same chemical composition, metal structure, and the like, only different from the above-described blank in the smoothing process. Therefore, the substrate according to the present embodiment is excellent in rigidity and smoothness of the electroless Ni-P plated film formed on the surface, like the blank described above.

[Blank manufacturing method]
The blank according to the present invention described above can be manufactured by a manufacturing method and equipment under general conditions for manufacturing a substrate for a magnetic disk. For example, a casting step of melting a material and adjusting it to the above-described chemical composition and casting an ingot, a homogenization heat treatment step of subjecting this ingot to a homogenization heat treatment, and a hot casting of the ingot subjected to the homogenization heat treatment. Hot rolling process to obtain a hot-rolled plate having a predetermined plate thickness by rolling, cold-rolling process to obtain a cold-rolled plate by cold-rolling the hot-rolled plate, and an annular substrate from the cold-rolled plate It can be manufactured by subjecting to a series of steps including a punching step of punching and a straightening annealing step of performing straightening annealing. If necessary, intermediate annealing may be performed before the cold rolling step or during the cold rolling step.

An example of specific conditions of each step described above will be described below, but the present invention is not limited to these.
In the casting process, it is preferable to melt the material at 700 to 800°C and cast at 700 to 800°C. The obtained ingot is preferably subjected to chamfering of 2 mm/one side.
The homogenizing heat treatment step is preferably performed at 400 to 600° C., preferably 540° C. for 8 hours.
The hot rolling step is continuously performed after the homogenizing heat treatment, but from the viewpoint of suppressing the Mg-Si intermetallic compound, the starting temperature is preferably 510°C or higher, and the ending temperature is preferably 300 to 350°C, preferably 520°C. It is preferable to pass from 3 to 400° C. within 3 hours. The plate thickness after rolling is preferably 3 mm or less.
In the cold rolling step, the plate thickness after rolling is preferably about 1 mm.
In the punching step, it is preferable to punch from a cold-rolled plate so as to form an annular substrate (for 3.5 inch HDD) having an inner diameter of 24 mm and an outer diameter of 96 mm. When manufacturing a blank for a 2.5-inch HDD, it is preferable to punch a cold-rolled plate into an annular substrate having an inner diameter of 19 mm and an outer diameter of 66 mm.
In the straightening annealing step, annular substrates are stacked between the spacers having high flatness, and the whole is annealed while being pressed. It is preferable that the annealing temperature is 300 to 500° C. and the annealing time is 3 hours. Further, it is preferable that both the temperature rising rate and the high temperature rate during the straightening annealing are 80° C./hour.

[Substrate manufacturing method]
The substrate according to the present invention described above can be manufactured, for example, as follows.
First, end face processing is performed by cutting the inner diameter and the outer diameter of the blank by 1 mm each. After that, the end-face processed blank is set in the pocket of the carrier that is preset in the double-sided grinder. Then, the substrate according to the present invention can be manufactured by performing grinding (mirror surface processing) to a target plate thickness with a grindstone (the substrate may also be referred to as a grind substrate). ).
The substrate thus produced according to the present invention has the same chemical composition and metallographic structure as the blank described above, but since it is mirror-finished, it has higher smoothness than the blank. doing.

[Magnetic Disk and Manufacturing Method Thereof]
The surface of the substrate thus manufactured was subjected to acid etching treatment under arbitrary conditions to form an electroless Ni-P plated film, and then the surface was polished (the electroless Ni-P plated film was formed. The substrate is sometimes called the plated substrate.) Then, a base film for enhancing 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 on this substrate by sputtering. A magnetic disk can be manufactured.
The formation of the electroless Ni-P plated film, the undercoat film, the magnetic film, and the protective film described above can be performed under the conditions generally used for manufacturing a magnetic disk.

The manufacturing conditions of the blank and the substrate are described in detail, for example, in Japanese Patent No. 3471557 and Japanese Patent No. 5199714. Therefore, it is possible to refer to these documents when manufacturing blanks and substrates.

Further, as described above, the difference between the blank and the substrate in the present invention is whether or not the grinding process (mirror finish) is performed. Therefore, the area ratio of the intermetallic compounds occupying the surface, the total value of the area ratios of the simple Si and Mg-Si intermetallic compounds occupying the surface, the measurement results of Young's modulus and the evaluation results, and the proof stress, which were performed on the substrate The measurement result and the evaluation result of can be regarded as the calculation result, the measurement result, and the evaluation result in the blank as they are, and vice versa.

Next, the blank and the substrate according to the present invention will be described in more detail by contrasting an example that exhibits the effects of the present invention and a comparative example that does not.
No. of Table 1 No. 1 to No. 15, 20, and 30 to 33 were used, and Al alloys having chemical compositions (mass %) were used. The substrates according to 1 to 15 and 30 to 33 were manufactured as follows. In addition, No. In No. 20, a substrate could not be manufactured because hot cracking occurred (see Table 2). Here, "-" in Table 1 indicates that the corresponding component was not added and the amount was below the detection limit value, and the underline indicates that the requirements of the present invention were not satisfied. In addition, in the calculation of “total amount of Fe, Mn, Ni” and “total amount of Cr, Ti, Zr” in Table 1, the content indicated by “−” was calculated as 0 mass %.

The substrate was manufactured by performing a casting process, a homogenizing heat treatment process, a hot rolling process, a cold rolling process, a punching process, a straightening annealing process, an end face working process, and a mirror finishing process in this order. The specific conditions of each step are as follows.

In the casting process, the material was melted and cast at 750°C. The obtained ingot was subjected to chamfering of 2 mm/one side.
The homogenizing heat treatment process is No. Nos. 1 to 15 and 20 were performed at 540° C. for 8 hours, and No. About 30-33, it performed at 450 degreeC for 8 hours, and after taking out from a furnace, the hot rolling was started within 5 minutes.
The hot rolling process is No. For 1 to 15 and 20, the starting temperature was 520 to 540° C., the ending temperature was 300 to 330° C., and the sheet thickness after rolling was 3 mm. No. For 30 to 33, the starting temperature was 430 to 450° C., the ending temperature was 300 to 330° C., and the plate thickness after rolling was 3 mm. In addition, in the case where hot cracking occurred in this hot rolling step (No. 20), the area ratio of the intermetallic compound occupying the surface and the area ratio of the simple Si and Mg-Si based intermetallic compound occupying the surface In order to examine the total of the above and the above, the unbroken portion was used for polishing, and the area ratio of the intermetallic compound was measured as described below. The value of the area ratio of the intermetallic compound does not change even if the hot rolled plate after hot rolling is measured or the blank after straightening annealing is measured.

The cold rolling process was performed so that the plate thickness after rolling was 1 mm.
In the punching process, the substrate was punched from a cold rolled plate into an annular shape (corresponding to the size of 3.5 inch HDD) having an inner diameter of 24 mm and an outer diameter of 96 mm.
The straightening annealing step was performed by stacking annular substrates between the spacers having high flatness and annealing the whole while applying pressure. The annealing temperature was 400° C., and the annealing time was 3 hours. In addition, the rate of temperature rise and the rate of high temperature during the straightening annealing were both 80° C./hour. A blank was manufactured by performing the casting process to the straightening annealing process.
Then, in the end face processing step, the inner diameter and the outer diameter of the blank were cut by 1 mm each.
Then, in the mirror surface processing step, the blank after the end surface processing is set in the pocket of the carrier previously set in the double-sided grinder, and the target plate thickness is obtained by the PVA whetstone (No. 4000 manufactured by NIPPON SPECIFIC TOOL CO., LTD.). Grinding (mirror surface processing) was performed until it became. A substrate was manufactured by performing this mirror surface processing step.

The manufactured No. Using the substrates according to 1 to 15 and 30 to 33, while obtaining the area ratio of the intermetallic compound occupying the surface and the total area ratio of the simple Si and Mg-Si based intermetallic compounds occupying the surface, The absolute maximum length of the intermetallic compound on the surface, Young's modulus, and proof stress were measured as follows. The smoothness of the electroless Ni-P plated film formed on the surface of the substrate was evaluated as follows.

(Area ratio of intermetallic compounds occupying surface, total area ratio of elemental Si and Mg-Si intermetallic compounds occupying surface)
The total area ratio of the intermetallic compounds on the surface and the total area ratio of the simple substance Si and the Mg—Si intermetallic compound on the surface were measured as follows. Using an FE-SEM (Field Emission Scanning Electron Microscope, model JSM-7001F) manufactured by JEOL Ltd., an accelerating voltage was set to 15 kV, and a composition image of 20 fields of view was taken at 200 times. Then, using the attached analysis system “Analysis Station 3,8,0,31” and particle analysis software “EX-35110 particle analysis software Ver. 3.84”, a simple substance in the composition image obtained by FE-SEM Area ratios of Si, Mg-Si based intermetallic compounds, Al-Fe based intermetallic compounds, etc. were calculated. Further, the area ratio of the intermetallic compound on the surface was calculated by appropriately summing the calculated area ratios of the intermetallic compounds.

(Absolute maximum length of intermetallic compound on the surface)
The absolute maximum length of the intermetallic compound on the surface is the distance between the two most distant points on the corresponding particle recognized by observing in the COMPO image of the SEM when calculating the area ratio of the intermetallic compound on the surface. Was measured.

(Young's modulus)
The Young's modulus was made in accordance with JIS Z 2280:1993 (high temperature Young's modulus test method for metallic materials), and a test piece of 60 mm×10 mm×1 mm thickness having a longitudinal direction parallel to the rolling direction was prepared and the test piece was used. Was measured. The measurement was performed by a free resonance method at room temperature in an air atmosphere using a JE-RT type manufactured by Nippon Techno Plus Co., Ltd. as a test device.
Those having a Young's modulus of 80 GPa or more were evaluated as “⊚”, those of 73 GPa or more and less than 80 GPa were evaluated as “◯”, and those of less than 73 GPa were evaluated as “x”. ⊚ and ◯ are passed, and x is not passed.

(Proof strength)
In addition, it is difficult to manufacture a test piece for proof stress measurement from the manufactured annular substrate due to shape and size reasons. Therefore, after cutting out a part of the cold-rolled sheet and annealing at 400° C. for 3 hours, which is equivalent to the straightening annealing, the rolling parallel direction is elongated in accordance with JIS Z 2241:2011 (metal material tensile test method). It was determined by making a JIS No. 5 test piece oriented in the direction and conducting a metal material tensile test.
Those having a proof stress of 120 MPa or more were evaluated as “⊚”, those having a yield strength of 100 MPa or more and less than 120 MPa were evaluated as “◯”, those having a yield strength of 90 MPa or more and less than 100 MPa were evaluated as “Δ”, and those of less than 90 MPa were evaluated as “x”. ⊚, ○ and Δ are passed, and × is not passed. In addition, the same value was obtained when a test piece was prepared by reducing a blank to a dimension ratio similar to the JIS No. 5 test piece and measuring it.

(Smoothness of electroless Ni-P plating film formed on the surface)
The manufactured substrate was degreased at 70° C. for 5 minutes with an alkaline cleaner (AD-68F manufactured by Uemura Kogyo Co., Ltd.) and then washed with pure water. Then, after performing an acid etching treatment at 68° C. for 2 minutes with a soft etching agent (AD-101F manufactured by Uemura Kogyo Co., Ltd.), it was washed with pure water.
Then, desmutting treatment was performed with 30% nitric acid, and subsequently, zincating treatment was performed at 20° C. for 30 seconds using a zincate treating liquid (AD-301F-3X manufactured by Uemura Kogyo Co., Ltd.). Then, Zn was once dissolved in 30% nitric acid, and then zincate treatment was performed again at 20° C. for 15 seconds using the above zincate treatment liquid. Then, an Ni-P plating solution (Nimden (registered trademark) HDX manufactured by Uemura Kogyo Co., Ltd.) is used, and electroless Ni-P plating is performed under the condition of 90° C. for 2 hours to obtain an electroless film having a thickness of about 10 μm. A Ni-P plated film was formed.
The plating surface of the substrate on which the electroless Ni-P plating film was formed was used in the objective lens x50, FOV x1, and VSI mode using a Bruker Contour GT X3 (non-contact three-dimensional optical interference type surface roughness meter). The surface was measured. The number of pits having a width of 3 μm or more and the depth of 1 μm or more on the surface of the plating film is 0 to 4/mm ² , “◎”, 5 to 10/mm ² is “○”, 11/mm ² or more What was evaluated as "x". ⊚ and ◯ are passed, and x is not passed.
The substrate after the electroless Ni-P plating film was formed was treated with a colloidal silica-based slurry (DISKLITE Z5601A manufactured by Fujimi Incorporated) and a pad (N0058 72D manufactured by Kanebo Corporation (currently Aion Co., Ltd.)). Even when polishing (polishing) was performed using and the surface thereof was used for evaluation, the evaluation result after the formation of the electroless Ni-P plated film was not different.

In Table 2, No. 1 to 15 and 30 to 33 show measurement results and evaluation results performed on the substrates (note that the substrate according to No. 20 suffered from hot cracking as described above, so Young's modulus, proof stress, The smoothness of the electroless Ni-P plated film formed on the surface was not evaluated or measured.). Here, underlining in Table 2 indicates that the requirements of the present invention are not satisfied.

As shown in Table 2, No. Since the substrates according to 1 to 12 satisfied the requirements of the present invention, it was confirmed that the intended effects of the present invention were exhibited (all examples).
Specifically, No. It was confirmed that the substrates according to 1, 2, 4 to 6, 9, and 11 had a good Young's modulus and were excellent in rigidity. Moreover, these also satisfied the proof stress value required as a blank.
In addition, No. It was confirmed that the substrates according to 1 to 12 have excellent smoothness of the electroless Ni-P plating film formed on the surface.
Among these, No. Since the substrate of No. 12 contained appropriate amounts of Cu and Zn, it was confirmed that the electroless Ni-P plated film formed on the surface tends to have high smoothness.

On the other hand, as shown in Table 2, No. Since the substrates of Nos. 13 to 15 and 30 to 33 did not satisfy the requirements of the present invention, it was confirmed that the Young's modulus or the smoothness of the electroless Ni-P plated film formed on the surface was inferior. (All are comparative examples).

Specifically, No. The substrate according to No. 13 had a low Young's modulus and poor rigidity because the amount of Mg exceeded the upper limit.
No. In the substrate according to No. 14, since the amount of Si exceeded the upper limit, the total area ratio of elemental Si and Mg-Si intermetallic compound on the surface exceeded the upper limit. Therefore, No. In the substrate of No. 14, the number of pits in the electroless Ni-P plated film formed on the surface was increased and the smoothness was poor. In addition, No. The substrate of No. 14 had low yield strength and poor strength.
No. Since the area ratio of the intermetallic compound occupying the surface of the substrate of No. 15 was less than the lower limit, the Young's modulus was low and the rigidity was poor.
No. In the substrates according to Nos. 30 to 33, the total area ratio of elemental Si and Mg-Si intermetallic compounds occupying the surface exceeded the upper limit, so the number of pits in the electroless Ni-P plated film formed on the surface increased. However, the smoothness was poor. In addition, No. The substrates according to Nos. 30 to 33 had low yield strength and poor strength.

As described above, No. The substrate of No. 20 could not be manufactured because hot cracking occurred (Comparative Example).
Specifically, No. In the substrate of No. 20, the total amount of Cr, Ti, and Zr exceeded the upper limit, so that hot cracking occurred.
No. where hot cracking occurred In the substrate of No. 20, the area ratio of the above-described intermetallic compound on the surface exceeded the upper limit.

Claims (13)

Mg: 3.00 mass% or less,
Si: 1.00 mass% or less,
Fe: 5.0% by mass or less, Mn: 5.0% by mass or less, Ni: 5.0% by mass or less, and the total amount thereof is 8.0% by mass or less,
Cr: 2.0% by mass or less, Ti: 0.5% by mass or less, Zr: 2.0% by mass or less, and the total amount thereof is 2.0% by mass or less,
The balance consists of Al and unavoidable impurities,
Of the unavoidable impurities, V, B, Na, K, Ca, and Sr are individually 0.005 mass% or less and 0.015 mass% or less in total,
An aluminum alloy plate for a magnetic disk, characterized in that the area ratio of the intermetallic compound occupying the surface is 5 to 40% and the total area ratio of the simple Si and Mg-Si based intermetallic compounds is 1% or less. The aluminum alloy plate for a magnetic disk according to claim 1, wherein the total amount of Fe, Mn, and Ni is 0.7% by mass or more and 8.0% by mass or less. The aluminum alloy plate for a magnetic disk according to claim 1 or 2, wherein the total amount of Cr, Ti, and Zr is 0.1% by mass or more and 2.0% by mass or less. Mg: 3.00 mass% or less,
Si: 0.20 mass% or less,
Fe: 5.0% by mass or less, Mn: 5.0% by mass or less, Ni: 5.0% by mass or less, and the total amount thereof is 8.0% by mass or less,
Cr: 2.0% by mass or less, Ti: 0.5% by mass or less, Zr: 2.0% by mass or less, and the total amount thereof is 2.0% by mass or less,
The balance consists of Al and unavoidable impurities,
An aluminum alloy plate for a magnetic disk, characterized in that the area ratio of the intermetallic compound occupying the surface is 5 to 40% and the total area ratio of the simple Si and Mg-Si based intermetallic compounds is 1% or less. The aluminum alloy plate for a magnetic disk according to claim 4, wherein the total amount of Fe, Mn, and Ni is 0.7% by mass or more and 8.0% by mass or less. The aluminum alloy plate for a magnetic disk according to claim 4 or 5, wherein the total amount of Cr, Ti, and Zr is 0.1% by mass or more and 2.0% by mass or less. Among the inevitable impurities, V, B, Na, K, Ca, and Sr are 0.005 mass% or less individually and 0.015 mass% or less in total, 5. 6. An aluminum alloy plate for a magnetic disk according to any one of 6. The Young's modulus is 73 GPa or more, and the aluminum alloy plate for a magnetic disk according to any one of claims 1 to 7. The aluminum alloy plate for a magnetic disk according to any one of claims 1 to 8, wherein the absolute maximum length of the intermetallic compound on the surface is 50 µm or less. Cu: 0.1% by mass or more and 10.0% by mass or less, Zn: 0.1% by mass or more and 10.0% by mass or less, at least one kind is contained, It is characterized by the above-mentioned. The aluminum alloy plate for a magnetic disk according to any one of the above. An aluminum alloy blank for a magnetic disk, comprising the aluminum alloy plate for a magnetic disk according to any one of claims 1 to 10. The aluminum alloy blank for a magnetic disk according to claim 11, which has a proof stress of 90 MPa or more. An aluminum alloy substrate for a magnetic disk, comprising the aluminum alloy blank for a magnetic disk according to claim 11 or 12.