JP6684198B2 - Aluminum alloy blanks for magnetic disks and aluminum alloy substrates for magnetic disks - Google Patents

Description

  The present invention relates to 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 thinned, there is a problem that vibration generated when the HDD is rotated tends to increase. 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 for increasing the 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 atomization 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) is performed near the melting temperature, followed by hot rolling to produce a plate having a predetermined plate thickness. In addition, since this method is inevitably processed one by one, there is a problem similar to that of the glass substrate that the production cost is inferior.

JP-A-63-183146

As described above, the invention described in Patent Document 1 is obtained by mixing matrix particles and reinforcing fibers and performing HIP treatment near the melting temperature. Therefore, the adhesion between the matrix particles and the reinforcing fibers is improved. 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 a magnetic disk blank that uses an aluminum rolled plate that is excellent in production cost.

  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. It is an object to provide an aluminum alloy substrate.

  As a result of earnest research for solving the above-mentioned 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. Further, 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 rigidity and at the same time suppress the occurrence of plating defects. Has been completed.

  The aluminum alloy blank for a magnetic disk according to the present invention, which has solved the above-mentioned problems, has Mg: 3.00 mass% or less, Si: 1.00 mass% or less, Fe: 6.0 mass% or less, and Mn: 10. 0 mass% or less, Ni: 10.0 mass% or less, at least one is contained, the total amount is 10.0 mass% or less, the balance is Al and unavoidable impurities, the metal occupying the surface It is assumed that the area ratio of the intermetallic compound is 5 to 40% and the total area ratio of the elemental Si and the Mg—Si based intermetallic compound is 1% or less.

  As described above, the aluminum alloy blank for a magnetic disk according to the present invention contains Mg at a predetermined value or less, and contains Fe, Mn, and Ni in a predetermined amount, and has a predetermined area ratio of the intermetallic compound on the surface. Since the range is set, the rigidity can be made excellent. Further, since Si is set to a predetermined value or less, it is possible to suppress the generation of elemental Si and the Mg-Si based intermetallic compound, and it is possible to obtain excellent rigidity. Further, since the aluminum alloy blank for a magnetic disk according to the present invention has a total area ratio of elemental Si and Mg—Si based intermetallic compounds occupying the surface of the blank, the electroless Ni—P plating formed on the surface is The number of pits formed in the film can be further reduced, and the plated film can have excellent smoothness.

  The aluminum alloy blank for a magnetic disk according to the present invention preferably has a Young's modulus of 73 GPa or more and a proof stress of 90 MPa or more.

  As described above, the aluminum alloy blank 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. Further, since the aluminum alloy blank for a magnetic disk according to the present invention has a proof stress of a predetermined value or more, it is possible to obtain a strength sufficient to maintain the impact resistance required for the magnetic disk.

  The aluminum alloy blank 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, in the aluminum alloy blank for a magnetic disk according to the present invention, the absolute maximum length of the intermetallic compound on the surface is not more than the predetermined value, so that the smoothness of the electroless Ni-P plated film formed on the surface is further improved. It can be excellent.

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

  As described above, the aluminum alloy blank for a magnetic disk according to the present invention contains a predetermined amount of Cu and Zn, so that the smoothness of the surface of the electroless Ni-P plated film formed on the surface of the blank (substrate) can be improved. It can be made even more excellent.

  The aluminum alloy substrate for a magnetic disk according to the present invention uses the aluminum alloy blank for a magnetic disk described in any one of the above.

  As described above, since the aluminum alloy substrate for a magnetic disk according to the present invention uses the above-described 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. The smoothness can be made excellent.

  The aluminum alloy blank for magnetic disks and the aluminum alloy substrate for magnetic disks according to the present invention have excellent rigidity and smoothness of the electroless Ni-P plating film formed on the surface.

  Hereinafter, a mode 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. The blank according to the present embodiment contains at least one of Fe: 6.0 mass% or less, Mn: 10.0 mass% or less, and Ni: 10.0 mass% or less, and the total amount thereof is It is set to 10.0 mass% or less. Further, the balance of the chemical composition of the blank according to the present embodiment consists of Al and inevitable impurities, and the blank according to the present embodiment is formed in a predetermined shape using the aluminum alloy having the above-described chemical composition.
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 elemental Si and the Mg-Si based intermetallic compound 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 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% by mass or less, and more preferably 1.00% by mass or less.
Further, Mg binds to Si as described later, and the amount of Mg-Si-based intermetallic compound produced increases. Therefore, from the viewpoint of suppressing this, the amount is set to 3.00% by mass or less as described above. From the viewpoint of suppressing the Mg-Si based 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 having 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 an ingot impurity, and in the step of casting the ingot of the Al alloy, simple Si and Mg-Si-based intermetallic compound 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 becomes too large. In such a case, it may not be possible to maintain the proof stress of a level required as a blank. Moreover, since the electroless Ni-P plating film is not coated on the simple substance Si and the Mg-Si based 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 mass% or less, more preferably 0.10 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, 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 one of Fe> 6.0 mass%, Mn> 10.0 mass% and Ni> 10.0 mass% is applicable, or if Fe + Mn + Ni> 10.0 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 plate during hot rolling. Therefore, at least one of Fe: 6.0 mass% or less, Mn: 10.0 mass% or less, and Ni: 10.0 mass% or less is contained and Fe + Mn + Ni ≦ 10.0 mass% is satisfied. .
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 process of plating, so from the viewpoint of plating smoothness, Fe ≦ 2.0 mass%, Mn ≦ 2.0 mass%, Ni ≦ 2. It is preferably 0% by mass, and preferably Fe + Mn + Ni ≦ 4.0% by mass. On the other hand, from the viewpoint of securing the Young's modulus, it is preferable that 1.3 mass% ≦ Fe + Mn + Ni.

(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 Cr, Ti, Zr, V, B, Na, K, Ca, and Sr. If the unavoidable impurities are 0.005 mass% or less individually, and 0.015 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 the range of less than 0.1% by mass, respectively.

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

(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 compounds, Al-Fe-Ni-based intermetallic compounds, Al-Mn-Ni-based intermetallic compounds, Al-Fe-Mn-Ni-based intermetallic compounds, and the like. 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, if 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 more excellent surface properties, the area ratio is preferably 38% or less, and more preferably 35% or less.

  The area ratio can be adjusted by adjusting the contents of Si, Mg, Fe, Mn, and Ni to be described in the present specification. When Cu and Zn are contained, these are added to the contents described in the present specification. It is possible to adjust by doing so (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 covered with the electroless Ni-P plating film as described above. Therefore, when 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. In addition, when the amount of elemental Si and the Mg—Si based intermetallic compound is large, it becomes difficult to set the proof stress of the aluminum alloy for a magnetic disk to 90 MPa or more. Therefore, in the present invention, the total area ratio of the elemental Si and the Mg—Si intermetallic compound 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 intermetallic compound can be controlled by adjusting the Si content to be equal to or less than the above content.

  The area ratio of each of the above-mentioned intermetallic compounds (including simple substance 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. 3.84”, a single substance in the composition image obtained by FE-SEM The area ratio of Si, Mg-Si based intermetallic compound, Al-Fe based intermetallic compound, etc. can be calculated.

(Young's modulus)
Young's modulus is the ratio of stress to strain when a material behaves elastically, and in the present invention, it affects the generation of vibration when a thin magnetic disk is rotated by an 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 adjusting the content of Mg, Fe, Mn, and Ni described in the present specification and by setting the area ratio of the intermetallic compound on the surface within 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 test piece of 60 mm × 10 mm × 1 mm thickness 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 the free resonance method at room temperature in the atmosphere according to the method specified by JIS. As the test device, it is preferable to use JE-RT type manufactured by Nippon Techno Plus Co.

(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 cannot be obtained as a blank. From the viewpoint of obtaining higher strength as a blank, the yield strength is preferably 100 MPa or higher, more preferably 110 MPa or higher, even more preferably 120 MPa or higher, even more preferably 130 MPa or higher.
The proof stress is obtained by adding the addition amount of Fe, Mn, Ni, Mg or the like within the above-mentioned predetermined amount range and adjusting the annealing conditions 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, in conformity with JIS Z 2241: 2011 (Metallic material tensile test method) by producing a JIS No. 5 test piece having the rolling parallel direction as the longitudinal direction and conducting a metallic material tensile test. When it is difficult to produce the test piece from a blank or a substrate, for example, a part of the cold-rolled sheet in the process of production is cut out and annealed at 320 ° C. for 3 hours corresponding to the 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 film 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 that is recognized when observed in a SEM COMPO image or the like. The smaller the absolute maximum length of the intermetallic compound, the less 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, etc. described in this 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-mentioned 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. When the Cu content and the Zn content each exceed 10.0 mass%, the amount of the intermetallic compound produced increases, which may cause hot cracking.

  The chemical composition of the blank according to the second embodiment, the area ratio of the intermetallic compound on the surface, the Young's modulus, the proof stress, and the total area ratio of the simple Si and Mg-Si based intermetallic compounds on the surface are the first The description is omitted because it is similar to 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 on the surface, and an area ratio of simple Si and Mg-Si based intermetallic compounds on the surface. The total and are specified as described above. Therefore, the blanks according to the first and second embodiments 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 and metal structure, etc., only different from the above-described blank in whether or not it is smoothed. 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 thereof, 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, the material is melted and adjusted to the above-described chemical composition, a casting step of casting an ingot, a homogenization heat treatment step of subjecting this ingot to a homogenization heat treatment, and a ingot subjected to the homogenization heat treatment Hot rolling process to obtain a hot rolled plate having a predetermined thickness by rolling, cold rolling process to obtain a cold rolled plate by cold rolling the hot rolled plate, annular substrate from the cold rolled plate It can be manufactured by subjecting to a series of processes including a punching process of punching and a straightening annealing process of performing straightening annealing. If necessary, intermediate annealing may be performed before the cold rolling process or during the cold rolling process.

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 about 2 mm / one side.
The homogenizing heat treatment step is preferably performed at 400 to 600 ° C., preferably about 540 ° C. for about 8 hours.
The hot rolling step is continuously performed after the homogenizing heat treatment, but from the viewpoint of suppressing the Mg—Si based intermetallic compound, the starting temperature is preferably 510 ° C. or higher, and the ending temperature is preferably 300 to 350 ° C., 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 the cold-rolled sheet into 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. The annealing temperature is preferably 300 to 500 ° C., and the annealing time is preferably 3 hours. Further, it is preferable that both the temperature rising rate and the high temperature rate at the time of performing the straightening annealing are about 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 outer diameter of the blank by 1 mm each. After that, the end-face processed blank is set in the pocket of the carrier 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. is 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 the substrate by sputtering, A magnetic disk can be manufactured.
The formation of the electroless Ni-P plating film, the undercoat film, the magnetic film, and the protective film described above can be performed under the conditions generally carried out in 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 The measurement result and the evaluation result can be regarded as the blank calculation result, the measurement result, and the evaluation result as they are, and vice versa.

Next, the blank and the substrate according to the present invention will be described in more detail in comparison with an example that exhibits the effects of the present invention and a comparative example that does not.
No. of Table 1 Using an Al alloy having the chemical composition (mass%) shown in Nos. 1 to 27, No. Substrates according to 1 to 7, 9, 11 to 16, 25 to 27 were manufactured as follows. In addition, No. No. 17 was not able to manufacture a substrate because hot cracking occurred (see Table 2). Here, "-" in Table 1 indicates that the corresponding component was not added and the amount was less than the detection limit value, and the underline indicates that the requirements of the present invention were not satisfied. Further, in the calculation of “the total amount of Fe, Mn, and Ni” in Table 1, each content of Fe, Mn, and Ni 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 chamfered on 2 mm / one side.
The homogenizing heat treatment process is No. For Nos. 1 to 7 , 9 and 11 to 17 , the test was performed at 540 ° C. for 8 hours, and Nos. 2 5 performed 8 hours at 450 ° C. for ~ 27 began hot rolling after removal from the furnace within 5 minutes.
The hot rolling process is No. For 1 to 7 , 9 and 11 to 17 , the starting temperature was set to 520 to 540 ° C, the ending temperature was set to 300 to 330 ° C, and the sheet thickness after rolling was set to 3 mm. No. For 25 to 27, 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. 17) , the area ratio of the intermetallic compound occupying the surface and the area of simple Si and Mg-Si based intermetallic compound occupying the surface In order to examine the total of the ratios, 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 sheet 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 out from a cold rolled plate into an annular shape having an inner diameter of 24 mm and an outer diameter of 96 mm (corresponding to the size of 3.5 inch HDD).
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. Further, both the temperature rising rate and the high temperature rate during the straightening annealing were 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 SPECIAL ENGINEERING 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 7, 9, 11 to 16, 25 to 27, of the area ratio of the intermetallic compound occupying the surface and the area ratio of the simple Si and Mg-Si based intermetallic compounds occupying the surface The total and 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 compound on the surface and the total area ratio of the simple substance Si and the Mg—Si based 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 acceleration 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 single substance in the composition image obtained by FE-SEM The area ratio of Si, Mg-Si based intermetallic compound, Al-Fe based intermetallic compound, etc. was 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 points that are most distant on the corresponding particle recognized by observing in the COMPO image of SEM when calculating the area ratio of the intermetallic compound occupying the surface. Was measured.

(Young's modulus)
Young's modulus was measured according to 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, a part of the cold-rolled sheet is cut out and annealed at 400 ° C. for 3 hours, which is equivalent to straightening annealing, and then the rolling parallel direction is lengthened 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. It should be noted that the same value was obtained when a test piece reduced from the blank to a dimension ratio similar to the JIS No. 5 test piece was prepared and measured.

(Smoothness of electroless Ni-P plating film formed on the surface)
The produced 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. Next, 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, using an Ni-P plating solution (Nimden (registered trademark) HDX manufactured by Uemura Kogyo Co., Ltd.), electroless Ni-P plating is performed under the conditions of 90 ° C. and 2 hours, and an electroless thickness of about 10 μm. A Ni-P plated film was formed.
The plated surface of the substrate on which the electroless Ni-P plated film was formed was used as an objective lens x 50, FOV x 1, 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 a 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. The above 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 if the surface was used for evaluation by polishing with (1) and (2), the evaluation result after forming the electroless Ni-P plated film was not different.

In Table 2, No. 1 to 7, 9, 11 to 16, and 25 to 27 show the measurement results and the evaluation results performed on the substrates (Note that, as described above, the substrate according to No. 17 has hot cracking). Therefore, the Young's modulus, the proof stress, and the smoothness of the electroless Ni-P plated film formed on the surface were not evaluated and measured). Here, underlines in Table 2 indicate that the requirements of the present invention are not satisfied.

As shown in Table 2, No. Since the substrates according to 1 to 13 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 of Nos. 2, 5, 6, and 12 had good Young's modulus and excellent rigidity. Moreover, these also satisfied the proof stress value required as a blank.
In addition, No. It was confirmed that the substrates according to Nos. 1 to 13 had excellent smoothness of the electroless Ni-P plating film formed on the surface.
Among these, No. Since the substrates according to 11 to 13 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 according to 14 to 16 and 25 to 27 did not satisfy the requirements of the present invention, the intended effects of the present invention could not be obtained (all comparative examples). For example, No. Substrate according to 14,2 5-27 is the smoothness of the electroless Ni-P plating film formed on the surface was inferior. No. The substrates of Nos. 15 and 16 had a poor Young's modulus and were inferior in rigidity.

More specifically, No. In the substrate according to No. 14, since the amount of Si exceeded the upper limit and the amount of Mg was relatively large, 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. The substrate of No. 15 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. 16, the area ratio of the intermetallic compound occupying the surface was less than the lower limit, so the Young's modulus was low and the rigidity was poor.
No. In the substrates according to Nos. 25 to 27, the total area ratio of elemental Si and Mg-Si intermetallic compounds occupying the surface exceeded the upper limit, so that 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 substrates of Nos. 25 to 27 had low yield strength and poor strength.

As described above, No. Substrate according to 1 7 could not be produced for hot cracking occurred (ratio Comparative Examples).
Specifically, No. In the substrate of No. 17, the total amount of Fe, Mn, and Ni exceeded the upper limit, so that hot cracking occurred .

Claims (5)

Mg: 3.00 mass% or less,
Si: 1.00 mass% or less,
Fe: 6.0% by mass or less, Mn: 10.0% by mass or less, Ni: 10.0% by mass or less, and the total amount thereof is 10.0% by mass or less,
The balance consists of Al and unavoidable impurities,
An aluminum alloy blank for a magnetic disk, characterized in that the area ratio of intermetallic compounds occupying the surface is 5 to 40% and the total area ratio of simple Si and Mg-Si based intermetallic compounds is 1% or less.   The aluminum alloy blank for a magnetic disk according to claim 1, wherein the Young's modulus is 73 GPa or more and the proof stress is 90 MPa or more.   The aluminum alloy blank for a magnetic disk according to claim 1 or 2, 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 blank for a magnetic disk according to any one of the above.   An aluminum alloy substrate for a magnetic disk, wherein the aluminum alloy blank for a magnetic disk according to any one of claims 1 to 4 is used.