JP6492216B1 - Aluminum alloy substrate for magnetic disk, method of manufacturing the same, and magnetic disk using the aluminum alloy substrate for magnetic disk - Google Patents

Abstract

An aluminum alloy substrate for a magnetic disk having good fluttering characteristics and strength, a method of manufacturing the same, and a magnetic disk using the aluminum alloy substrate for the magnetic disk are provided.
An aluminum alloy comprising Fe: 0.05 to 3.00 mass%, Zr: 0.01 to 0.50 mass%, and an aluminum alloy composed of the balance Al and unavoidable impurities, and having a longest diameter of 1 μm or more An aluminum alloy substrate for a magnetic disk characterized in that the distribution density of the Zr-based intermetallic compound is 1 / mm ² or less, a method of manufacturing the same, and an electroless Ni—on the surface of the aluminum alloy substrate for the magnetic disk. A magnetic disk provided with a P-plated layer and a magnetic layer thereon.
[Selected figure] Figure 1

Description

  The present invention relates to an aluminum alloy substrate for a magnetic disk having good fluttering characteristics and strength, a method of manufacturing the same, and a magnetic disk using the aluminum alloy substrate for the magnetic disk.

  A magnetic disk used for a storage device of a computer is manufactured using a substrate having excellent plating properties and excellent mechanical characteristics and processability. For example, JIS 5086 (Mg: 3.5 to 4.5 mass%, Fe: 0.50 mass% or less, Si: 0.40 mass% or less, Mn: 0.20 to 0.70 mass%, Cr: 0.05 to 0. Manufactured from a substrate based on an aluminum alloy containing 25 mass%, Cu: 0.10 mass% or less, Ti: 0.15 mass% or less, Zn: 0.25 mass% or less, the balance being Al and unavoidable impurities) It is done.

  A common magnetic disk is manufactured by first producing an annular aluminum alloy substrate, plating the aluminum alloy substrate, and then depositing a magnetic material on the surface of the aluminum alloy substrate.

  For example, the aluminum alloy magnetic disk made of the JIS 5086 alloy is manufactured by the following manufacturing process. First, an aluminum alloy material having a predetermined chemical component is cast, the ingot is hot-rolled, and then cold-rolled to produce a rolled material having a thickness necessary for a magnetic disk. The rolled material is preferably annealed during cold rolling as needed. Next, this rolled material is punched into an annular shape, and in order to remove distortion and the like generated in the manufacturing process, an annular aluminum alloy sheet is laminated, and annealing is performed while pressing from both surfaces of both ends for flattening. Pressure annealing is performed to produce an annular aluminum alloy substrate.

  The annular aluminum alloy substrate thus produced is subjected to cutting, grinding, degreasing, etching, and zincate treatment (Zn substitution treatment) as pretreatment, and then Ni-P which is a hard nonmagnetic metal as an undercoating treatment Is electrolessly plated, and the plated surface is polished, and then a magnetic material is sputtered onto the Ni-P electrolessly plated surface to produce an aluminum alloy magnetic disk.

  By the way, in recent years, from the needs of multimedia and the like, the magnetic disk has been required to have a large capacity, high density, and high speed. In order to increase the capacity, the number of magnetic disks mounted in storage devices is increasing, and along with this, thinning of the magnetic disks is also required.

  However, as the thickness is reduced and the speed is increased, the excitation force is increased along with the decrease in rigidity and the increase in fluid force due to high speed rotation, and disk flutter is likely to occur. This is because when the magnetic disk is rotated at high speed, an unstable air flow is generated between the disks, and the air flow causes vibration (fluttering) of the magnetic disk. Such a phenomenon is considered to occur because when the rigidity of the substrate is low, the vibration of the magnetic disk becomes large and the head can not follow the change. When fluttering occurs, the positioning error of the head which is the reading unit increases. Therefore, there is a strong demand for reduction of disk flutter.

  In addition, as the density of the magnetic disk increases, the magnetic area per bit is further miniaturized. Along with this miniaturization, read errors due to misalignment of head positioning errors are likely to occur, and reduction of disk flutter, which is a main factor of head positioning errors, is strongly demanded.

  Furthermore, since the strength decreases when the aluminum alloy substrate for magnetic disks is thinned, there is also a demand for higher strength of the aluminum alloy substrate. In addition, the field of storage devices is exposed to intense cost competition, and cost reduction due to improvement of productivity etc. is strongly demanded.

  Under such circumstances, in recent years, an aluminum alloy substrate for a magnetic disk having a characteristic of small disk flutter is strongly desired and studied. For example, it has been proposed to mount an air flow suppressing component having a plate facing the disk in a hard disk drive. Patent Document 1 proposes a magnetic disk drive in which an air spoiler is installed on the upstream side of an actuator. The air spoiler reduces the air flow toward the actuator on the magnetic disk to reduce wind noise from the magnetic head. The air spoiler also suppresses disk flutter by weakening the air flow over the magnetic disk. Further, Patent Document 2 proposes a method of improving the rigidity by containing a large amount of Si which contributes to the improvement of the rigidity of the aluminum alloy plate.

Japanese Patent Application Laid-Open No. 2002-313061 WO 2016/068293 gazette

  However, in the method disclosed in Patent Document 1, the fluttering suppression effect is different due to the difference between the installed air spoiler and the magnetic disk substrate, and high accuracy of the parts is required, thus increasing the cost of parts. I am invited.

  Further, the method of containing a large amount of Si shown in Patent Document 2 is effective for rigidity improvement, but since a large number of Si particles having high hardness are present, the grinding property is reduced compared to JIS 5086 alloy, and the manufacturing cost is increased. Are invited. In addition, at present, sufficient strength can not be obtained with Si alone.

  The present invention has been made in view of the above situation, and an object thereof is to provide an aluminum alloy substrate for a magnetic disk excellent in fluttering characteristics and strength of the disk, and a magnetic disk using the same.

That is, the present invention comprises an aluminum alloy according to claim 1, containing Fe: 0.05 to 3.00 mass%, Zr: 0.01 to 0.50 mass%, and the balance Al and inevitable impurities, A distribution density of the Al-Zr based intermetallic compound having the longest diameter is 1 piece / mm ² or less.

  In the present invention according to claim 2, the aluminum alloy according to claim 1 comprises Mn: 0.1 to 3.0 mass%, Si: 0.1 to 0.4 mass%, Mg: 0.1 to 0.4 mass%, Containing one or more selected from the group consisting of Cu: 0.005 to 0.500 mass%, Ni: 0.1 to 3.0 mass%, and Cr: 0.01 to 1.00 mass% And

  In the present invention according to claim 3 according to claim 1 or 2, the aluminum alloy further contains Zn: 0.005 to 1.000 mass.

  The present invention according to claim 4 in any one of claims 1 to 3 wherein the aluminum alloy is selected from the group consisting of Ti, B and V, the total content of which is 0.005 to 0.500 mass%. It further contains one or two or more.

  In the present invention according to claim 5, an electroless Ni-P plated layer and a magnetic layer thereon are provided on the surface of the aluminum alloy substrate for magnetic disk according to any one of claims 1 to 4. The magnetic disk is characterized by

  The present invention is the method for producing an aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4 in claim 6, wherein the ingot is cast by a semi-continuous casting method using the aluminum alloy. Semi-continuous casting process, hot-rolling process for hot-rolling semi-continuous-cast ingot, cold-rolling process for cold-rolling hot-rolled plate, and disc blank for punching cold-rolled plate into an annular shape A punching process, a pressure annealing process for pressure annealing the punched disk blank, and a cutting and grinding process for cutting and grinding the pressure annealed disk blank, wherein the casting process is performed at 660 to 680 ° C. The molten metal holding time in the temperature range of 5 minutes or less is set to 5 minutes or less.

  The present invention according to claim 7 is a homogenization heat treatment according to claim 6, wherein the semicontinuously cast ingot is heat treated at 280 to 620 ° C. for 0.5 to 60 hours between the semicontinuous casting step and the hot rolling step. The process was further included.

  The eighth aspect of the present invention is that in the sixth or seventh aspect, the start temperature of the hot rolling step is 250 to 600 ° C., and the end temperature is 230 to 450 ° C.

  The present invention according to claim 9 is an annealing treatment step according to any one of claims 6 to 8 in which the rolled sheet is annealed before or during the cold rolling, and is 0.1 to 300 ° C. to 500 ° C. It further included a 30-hour batch annealing step or a continuous annealing step at 400-600 ° C. for 0-60 seconds.

  The present invention according to claim 10 is a method of manufacturing an aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4, wherein a cast sheet is cast by a continuous casting method using the aluminum alloy. A continuous casting process, a cold rolling process for cold rolling a continuously cast cast plate, a disk blank punching process for punching the cold rolled plate in an annular shape, and a pressure annealing process for pressure annealing the punched disk blank A cutting / grinding step of subjecting the pressure-annealed disk blank to cutting and grinding; and in the casting step, the molten metal holding time in the temperature range of 660 to 680 ° C. is 5 minutes or less. The method of manufacturing an aluminum alloy substrate for a magnetic disk is described.

  The present invention according to claim 11 is an annealing treatment step of annealing a cast sheet or cold rolled sheet before or during the cold rolling according to claim 10 in claim 10, wherein the annealing step is performed at 300 to 500 ° C. for 0.1 to 30 hours. Or a continuous annealing process at 400 to 600 ° C. for 0 to 60 seconds.

  The present invention can provide an aluminum alloy substrate for a magnetic disk excellent in fluttering characteristics and strength of the disk, a method of manufacturing the same, and a magnetic disk using the aluminum alloy substrate for the magnetic disk.

It is a flowchart which shows the manufacturing method of the aluminum alloy substrate for magnetic discs concerning this invention, and a magnetic disc, A semicontinuous casting method is used in a casting process in (a), A continuous casting method is used in a casting process in (b) Be

The present inventors focused on the relationship between the fluttering characteristics of the substrate and the material of the substrate and conducted intensive research on the relationship between these characteristics and the characteristics of the substrate (magnetic disk material). As a result, it has been found that the Fe content, the Zr content, and the size distribution of the Al-Zr based intermetallic compound greatly affect the fluttering characteristics and the strength. As a result, the inventors of the present invention have an Fe content of 0.05 to 3.00 mass% (hereinafter abbreviated as "%") and a Zr content of 1 μm or more within a range of 0.01 to 0.50%. It has been found that the fluttering characteristics and the strength are improved in the aluminum alloy substrate for a magnetic disk in which the distribution density of the Al-Zr based intermetallic compound having the longest diameter of 1 is 1 piece / mm ² or less. Based on these findings, the present inventors have completed the present invention.

A. Aluminum Alloy Substrate for Magnetic Disk Hereinafter, an aluminum alloy substrate for magnetic disk according to the present invention (hereinafter, simply referred to as “aluminum alloy substrate according to the present invention” or simply “aluminum alloy substrate”) will be described in detail.

1. Alloy Composition The aluminum alloy component of the aluminum alloy substrate for a magnetic disk using the Al-Fe-Zr alloy according to the present invention and the content thereof will be described below.

Fe:
Fe is an essential element, and is mainly present as second phase particles (Al-Fe based intermetallic compounds etc.), partially existing in solid solution in the matrix, and improving the strength and fluttering characteristics of the aluminum alloy substrate. Demonstrate. When vibration is applied to such a material, the viscous energy at the interface between the second phase particles and the matrix causes the vibration energy to be absorbed rapidly, resulting in very good fluttering characteristics. If the Fe content in the aluminum alloy is less than 0.05%, sufficient strength and fluttering characteristics can not be obtained. On the other hand, when the Fe content exceeds 3.00%, a large number of coarse Al-Fe based intermetallic compound particles are generated. Since the Al-Fe based intermetallic compound has a hardness higher than that of the aluminum matrix, it is difficult to cut, which causes a reduction in the grinding rate at the time of grinding, resulting in an increase in production cost. In addition, such coarse Al-Fe based intermetallic compound particles fall off during etching, zincate processing, cutting processing or grinding processing and a large dent is generated, resulting in the smoothness of the plated surface due to the occurrence of plating pits. And the peeling of plating. Moreover, the processability fall in a rolling process also arises. Therefore, the Fe content in the aluminum alloy is in the range of 0.05 to 3.00%. The Fe content is preferably in the range of 0.10 to 1.80%, more preferably 0.20 to 1.50%.

Zr:
Zr is an essential element and is mainly present as second phase particles (Al-Zr based intermetallic compounds), partially existing in solid solution in the matrix, and exerts the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate Do. When vibration is applied to such a material, the viscous energy at the interface between the second phase particles and the matrix causes the vibration energy to be absorbed rapidly, resulting in very good fluttering characteristics. If the Zr content in the aluminum alloy is less than 0.01%, sufficient strength can not be obtained. On the other hand, when the Zr content exceeds 0.50%, a large number of coarse Al-Zr based intermetallic compound particles are generated. Since the Al-Zr based intermetallic compound has a hardness higher than that of an aluminum matrix, it is difficult to shave, which causes a reduction in the grinding rate at the time of grinding and causes an increase in production cost. In addition, such coarse Al-Zr based intermetallic compound particles fall off during etching, zincate processing, cutting processing or grinding processing and a large depression is generated, and the smoothness of the plating surface due to the occurrence of plating pits And the peeling of plating. Moreover, the processability fall in a rolling process also arises. Therefore, the Zr content in the aluminum alloy is in the range of 0.01 to 0.50%. The Zr content is preferably in the range of 0.02 to 0.30%, more preferably 0.03 to 0.30%.

  Mn: 0.1 to 3.0%, Si: 0.1 to 0 as a first selective element to further improve the fluttering characteristics and strength of the aluminum alloy substrate for a magnetic disk, and further, the plating property. .4%, Mg: 0.1 to 0.4%, Cu: 0.005 to 0.500 mass%, Ni: 0.1 to 3.0% and Cr: 0.01 to 1.00% It may further contain one or more selected from Further, Zn: 0.005 to 1.000 mass may be further contained as a second selective element. Furthermore, as the third selective element, one or more selected from the group consisting of Ti, B, and V having a total content of 0.005 to 0.500% may be further contained. These selected elements are described below.

Mn:
Mn is mainly present as second phase particles (such as Al-Mn based intermetallic compounds), and exhibits an effect of improving the strength and fluttering characteristics of the aluminum alloy substrate. When vibration is applied to such a material, the viscous energy at the interface between the second phase particles and the matrix causes the vibration energy to be absorbed rapidly, resulting in very good fluttering characteristics. When the Mn content in the aluminum alloy is 0.1% or more, the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate can be further enhanced. In addition, when the Mn content in the aluminum alloy is 3.0% or less, the formation of a large number of coarse Al-Mn based intermetallic compound particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse Al-Mn based intermetallic compound particles are prevented from falling off and forming a large depression during etching, zincate processing, cutting processing or grinding processing, and the smoothness of the plating surface is improved. It is possible to further suppress the occurrence of reduction and peeling of plating. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the Mn content in the aluminum alloy is preferably in the range of 0.1 to 3.0%, and more preferably in the range of 0.1 to 1.0%.

Si:
Si is mainly present as second phase particles (Si particles, Mg-Si based intermetallic compounds, etc.), and exhibits the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate. When vibration is applied to such a material, the viscous energy at the interface between the second phase particles and the matrix causes the vibration energy to be absorbed rapidly, resulting in very good fluttering characteristics. When the Si content in the aluminum alloy is 0.1% or more, the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate can be further enhanced. In addition, when the Si content in the aluminum alloy is 0.4% or less, the formation of a large number of coarse second phase particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse second phase particles are prevented from falling off and forming a large depression during etching, zincate processing, cutting processing or grinding processing, thereby reducing the smoothness of the plating surface and peeling of plating. Can be further suppressed. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the Si content in the aluminum alloy is preferably in the range of 0.1 to 0.4%, and more preferably in the range of 0.1 to 0.3%.

Mg:
Mg forms a solid solution in the matrix or exists as second phase particles (such as Mg-Si based intermetallic compounds), and exhibits the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate. When the Mg content in the aluminum alloy is 0.1% or more, the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate can be further enhanced. In addition, when the Mg content in the aluminum alloy is 0.4% or less, the formation of a large number of coarse second phase particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse second phase particles are prevented from falling off and generating a large depression during etching, zincate processing, cutting processing or grinding processing, and the surface of the plated surface is reduced in smoothness and plating peeling. The occurrence can be further suppressed. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the content of Mg in the aluminum alloy is preferably in the range of 0.1 to 0.4%, and more preferably in the range of 0.1% to 0.3%.

Ni:
Ni is mainly present as second phase particles (Al--Ni-based intermetallic compound etc.) and exhibits an effect of improving the strength and fluttering characteristics of the aluminum alloy substrate. When vibration is applied to such a material, the viscous energy at the interface between the second phase particles and the matrix causes the vibration energy to be absorbed rapidly, resulting in very good fluttering characteristics. When the Ni content in the aluminum alloy is 0.1% or more, the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate can be further enhanced. In addition, when the Ni content in the aluminum alloy is 3.0% or less, the formation of a large number of coarse Al-Ni-based intermetallic compound particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse Al-Ni-based intermetallic compound particles are prevented from falling off and forming a large depression during etching, zincate processing, cutting processing or grinding processing, and the smoothness of the plating surface is improved. It is possible to further suppress the occurrence of reduction and peeling of plating. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the content of Ni in the aluminum alloy is preferably in the range of 0.1 to 3.0%, and more preferably in the range of 0.1 to 1.0%.

Cu:
Cu is mainly present as second phase particles (Al--Cu based intermetallic compounds etc.), and exhibits the effect of improving the strength and Young's modulus of the aluminum alloy substrate. In addition, the amount of Al dissolved during zincate treatment is reduced. Furthermore, the zincate film is uniformly, thinly and precisely attached, and the effect of improving the smoothness in the plating step of the next step is exhibited. When the Cu content in the aluminum alloy is 0.005% or more, the effect of improving the Young's modulus and the strength of the aluminum alloy substrate and the effect of improving the smoothness can be further enhanced. In addition, when the Cu content in the aluminum alloy is 0.500% or less, the formation of a large number of coarse Al-Cu-based intermetallic compound particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse Al-Cu based intermetallic compound particles are prevented from falling off and forming a large depression during etching, zincate treatment, cutting or grinding, and the smoothness of the plating surface It is possible to further enhance the effect of improving the corrosion resistance and to further suppress the occurrence of plating peeling. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the Cu content in the aluminum alloy is preferably in the range of 0.005 to 0.500%, and more preferably in the range of 0.005 to 0.300%.

Cr:
Cr is mainly present as second phase particles (Al-Cr-based intermetallic compound etc.), and exhibits the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate. When the Cr content in the aluminum alloy is 0.01% or more, the effect of improving the strength and fluttering characteristics of the aluminum alloy substrate can be further enhanced. Further, when the Cr content in the aluminum alloy is 1.00% or less, the formation of a large number of coarse Al-Cr based intermetallic compound particles is suppressed. As a result, it is possible to further suppress an increase in production cost due to a reduction in the grinding rate caused by the formation of a large number of intermetallic compounds. In addition, such coarse Al-Cr based intermetallic compound particles are prevented from falling off and forming a large depression during etching, zincate processing, cutting processing or grinding processing, and the smoothness of the plated surface is lowered. And the occurrence of plating peeling can be further suppressed. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the Cr content in the aluminum alloy is preferably in the range of 0.01 to 1.00%, and more preferably in the range of 0.10 to 0.50%.

Zn:
Zn has the effect of reducing the amount of Al dissolved during zincate treatment, and causing the zincate coating to adhere uniformly, thinly and precisely, and improving the smoothness and adhesion in the plating step of the next step. In addition, it forms second phase particles with other additive elements and exhibits the effect of improving Young's modulus and strength. When the Zn content in the aluminum alloy is 0.005% or more, the Al dissolution amount at the time of zincate treatment is reduced, and the zincate film is uniformly, thinly and precisely attached to improve the plating smoothness. The effect can be further enhanced. In addition, when the Zn content in the aluminum alloy is 1.000% or less, it is possible to further suppress the zincate coating from becoming uniform and to reduce the smoothness of the plating surface, and to cause plating peeling. It can be further suppressed. Moreover, the workability fall in a rolling process can be suppressed further. Therefore, the Zn content in the aluminum alloy is preferably in the range of 0.005 to 1.000%, and more preferably in the range of 0.100 to 0.700.

Ti, B, V
Ti, B and V form second phase particles (a boride such as TiB ₂ or Al ₃ Ti or Ti-V-B particles, etc.) in the solidification process at the time of casting, and these form crystal nuclei Therefore, it is possible to refine the crystal grains. As a result, the plating property is improved. In addition, as the crystal grains become finer, the nonuniformity of the size of the second phase particles is reduced, and the effect of reducing the variation in strength and fluttering characteristics in the aluminum alloy substrate is exhibited. However, if the total content of Ti, B and V is less than 0.005%, the above effect can not be obtained. On the other hand, even if the total content of Ti, B and V exceeds 0.500%, the effect is saturated and no further remarkable improvement effect can not be obtained. Therefore, the total content of Ti, B and V when adding Ti, B and V is preferably in the range of 0.005 to 0.500%, and in the range of 0.005 to 0.100%. It is more preferable to The total amount is the amount of one of Ti, B and V when it contains only one of them, and the total amount of these two when it contains two of them. When it contains all three types, it is a total amount of these three types.

Other elements:
Moreover, the remainder of the aluminum alloy used in the present invention consists of Al and unavoidable impurities. Here, the unavoidable impurities include Ga, Sn, etc., and if each is less than 0.10% and the total is less than 0.20%, the characteristics as the aluminum alloy substrate obtained in the present invention are impaired. There is nothing to do.

2. Next, the distribution of intermetallic compounds in the aluminum alloy substrate for a magnetic disk according to the present invention will be described.

In the aluminum alloy substrate for a magnetic disk according to the present invention, the distribution density of the Al-Zr based intermetallic compound having the longest diameter of 1 μm or more in the metal structure is defined to 1 / mm ² or less.

Here, the Al-Zr-based intermetallic compound defined in the present invention refers to a compound which can be confirmed to contain aluminum (Al) and zirconium (Zr) by WDS analysis of an electron beam microanalyzer (EPMA). Further, in the present invention, the longest diameter means, first, in an outline of an Al-Zr-based intermetallic compound obtained by analysis with a wavelength dispersive X-ray spectrometer (WDS) of an electron beam microanalyzer (EPMA). The maximum value of the distance between one point and another point on the outline is measured, and then this maximum value is measured for all points on the outline, and finally, the largest value selected from among these all maximum values I say something.
→ How to measure distribution density?

In the aluminum alloy substrate for a magnetic disk according to the present invention, the strength can be improved by setting the distribution density of the Al-Zr based intermetallic compound having the longest diameter of 1 μm or more in the metal structure to 1 piece / mm ² or less. .

With regard to Al-Zr-based intermetallic compounds, if it is a fine compound, it contributes to the strength improvement by the interaction with the dislocation, but a coarse compound having a longest diameter of 1 μm or more does not have the interaction with the dislocation and improves the strength. It hardly contributes. In addition, when a large number of coarse compounds exist, the Zr solid solution amount decreases, and the strength can not be improved. When the distribution density of the Al-Zr-based intermetallic compound having the longest diameter of 1 μm or more exceeds 1 piece / mm ² , the Zr solid solution amount decreases and the strength decreases. If the strength is lowered, the substrate is deformed at the time of grinding or at the time of polishing after plating and the like, which is unsuitable as a magnetic disk. Therefore, the distribution density of the Al-Zr based intermetallic compound having the longest diameter of 1 μm or more is defined to 1 / mm ² or less. Moreover, it is preferable to make this distribution density into 0 piece / mm < ² >.

3. Fluttering Characteristics Next, fluttering characteristics are also affected by motor characteristics of the hard disk drive. In the present invention, the fluttering property in air is preferably 50 nm or less, and more preferably 30 nm or less. If it is 50 nm or less, it is judged that it can withstand the use for general HDD. When it exceeds 50 nm, the positioning error of the head which is a reading unit increases.

  In addition, the fluttering property is preferably 30 nm or less in helium, and more preferably 20 nm or less. If it is 30 nm or less, it is judged that it can withstand the use for general HDD. When it exceeds 30 nm, the positioning error of the head which is a reading unit increases.

  Here, since the required fluttering characteristics differ depending on the hard disk drive to be used, the distribution state of the intermetallic compound may be determined appropriately for the fluttering characteristics. These can be obtained by appropriately adjusting the content of the additive element, the casting method including the cooling rate at the time of casting described below, and the heat history and processing history of the subsequent heat treatment and processing.

  In the embodiment of the present invention, the thickness of the aluminum alloy substrate is preferably 0.35 mm or more. If the thickness of the aluminum alloy substrate is less than 0.35 mm, the substrate may be deformed due to an acceleration force due to a drop or the like generated when attaching a hard disk drive. However, it is not this limitation if deformation can be suppressed by further increasing the proof stress. If the thickness of the aluminum alloy substrate exceeds 1.30 mm, although fluttering characteristics are improved, the number of disks that can be mounted in the hard disk decreases, which is not preferable. Therefore, the thickness of the aluminum alloy substrate is more preferably 0.35 to 1.30 mm, and still more preferably 0.50 to 1.00 mm.

  The fluid force can be reduced by filling the hard disk with helium. This is because the gas viscosity of helium is as small as about 1/8 that of air. The fluttering generated by the flow of gas accompanying the rotation of the hard disk is reduced by reducing the fluid force of the gas.

4. Next, the yield strength of the aluminum alloy substrate for a magnetic disk according to the present invention will be described. The aluminum alloy substrate according to the present invention is manufactured in the steps up to S108 shown in FIGS. 1 (a) and 1 (b), but is heat-treated in the subsequent steps up to S111. Such heating changes the mechanical strength, but the mechanical strength necessary for the finally obtained magnetic disk is defined as the resistance after heating at 270 ° C. in the atmosphere for 3 hours. In the following, the step numbers refer to both (a) and (b) of FIG. 1 unless otherwise specified.

  In the aluminum alloy substrate according to the present invention, the proof stress after heating at 270 ° C. for 3 hours in the atmosphere is preferably 80 MPa or more. In this case, the effect of further suppressing the deformation of the substrate at the time of manufacturing the magnetic disk is exhibited. When the proof stress of the aluminum alloy substrate is less than 80 MPa, there is a possibility that the aluminum alloy substrate may be deformed due to the application of an external force at the time of conveyance, attachment or the like. Therefore, the yield strength of the aluminum alloy substrate after heating at 270 ° C. in the atmosphere for 3 hours is preferably 80 MPa or more, more preferably 90 MPa or more, and still more preferably 100 MPa or more.

  The heating temperature indicating the proof stress is set to 270 ° C. because the heat treatment is performed in the steps from the preparation of the aluminum alloy substrate for a magnetic disk (step S108 in FIG. 1) to the adhesion of the magnetic body (step S111 in FIG. 1). Then, since the temperature is at most about 270 ° C., it is specified as a proof stress when heated at 270 ° C. The upper limit of the proof stress is not particularly limited, but is naturally determined by the alloy composition and manufacturing conditions, and is about 300 MPa in the present invention.

B. Method of Manufacturing Aluminum Alloy Substrate for Magnetic Disk Hereinafter, each process and process condition of the manufacturing process of the aluminum alloy substrate for magnetic disk according to the present invention will be described in detail.

  A method of manufacturing a magnetic disk using an aluminum alloy substrate will be described according to the flow of FIG. Here, (a) melting of aluminum alloy melt (step S101) to cold rolling (step S105), and (b) melting of aluminum alloy melt (step S101), continuous casting of aluminum alloy (step S101) S102) and cold rolling (step S105) are steps for producing an aluminum alloy plate, and the production of a disk blank (step S106) to the attachment of a magnetic body (step S111) are performed on the produced aluminum alloy plate as a magnetic disk It is a process to Although any of the steps affects the distribution of the Al-Zr based intermetallic compound, the present inventors have found that the semi-continuous casting process of step S102 in (a) and the continuous casting process of step S102 in (b) Particular attention was paid to the retention time and temperature in

  First, the process of manufacturing an aluminum alloy sheet will be described. First, a molten metal of an aluminum alloy material having the above-described component composition is melted and produced by heating and melting according to a conventional method (step S101). Next, an aluminum alloy is cast from the molten aluminum alloy material by a semi-continuous casting (DC casting) method or a continuous casting (CC casting) method (step S102). Here, the DC casting method and the CC casting method are as follows.

  In the DC casting method, the molten metal poured through the spout is deprived of heat by the bottom block, the wall of the water-cooled mold, and the cooling water discharged directly to the outer peripheral portion of the ingot (ingot), thereby solidifying. And drawn downward as an ingot.

  In the CC casting method, molten metal is supplied through a casting nozzle between a pair of rolls (or belt casters, block casters), and thin sheets are directly cast by heat removal from the rolls.

  The major difference between the DC casting method and the CC casting method is the cooling rate at the time of casting. The CC casting method, which has a high cooling rate, is characterized in that the size of the second phase particles is smaller than that of DC casting.

  In the present invention, in the casting step, the molten metal holding time in the temperature range of 660 to 680 ° C. is set to 5 minutes or less. Al-Zr-based intermetallic compounds are easily formed in a temperature range of 660 to 680 ° C., and coarsened when held for a long time. Therefore, in order to suppress the formation of coarse Al-Zr based intermetallic compounds, it is effective to shorten the molten metal holding time in the temperature range of 660 to 680 ° C, and the molten metal is effective from the start to the end of the casting process. Temperature control is performed and controlled so that the time in the above temperature range is 5 minutes or less. This can suppress the formation of coarse Al-Zr based intermetallic compounds. If the temperature of the molten metal is less than 660 ° C., the raw material is not completely melted, which is unsuitable as a magnetic disk. Therefore, the molten metal temperature needs to be in the temperature range of 660 to 680 ° C. Moreover, in the case where the temperature of the molten metal is 660 to 680 ° C., when the holding temperature exceeds 5 minutes, coarse Al-Zr based intermetallic compounds are easily generated. As a result, the solid solution amount of Zr decreases and the strength decreases. If the strength is lowered, the substrate is deformed at the time of grinding or at the time of polishing after plating and the like, which is unsuitable as a magnetic disk. Therefore, the molten metal holding time in the temperature range of 660 to 680 ° C. is specified to be 5 minutes or less. The molten metal holding time in the temperature range of 660 to 680 ° C. is preferably 3 minutes or less. The lower limit is not particularly limited, but in the present invention, it is about 1 minute.

  As shown in FIG. 1 (a), a homogenization process is carried out on the DC-cast aluminum alloy ingot as required (step S103). When performing a homogenization process, it is preferable to perform the heat processing at 280-620 degreeC for 0.5 to 60 hours, and it is more preferable to perform the heat processing at 300-620 degreeC for 1 to 24 hours. When the heating temperature during homogenization is less than 280 ° C. or the heating time is less than 0.5 hours, the homogenization is insufficient, and the variation in attenuation ratio among the aluminum alloy substrates becomes large, and the fluttering characteristics vary. There is also a risk that If the heating temperature at the time of the homogenization treatment exceeds 620 ° C., melting may occur in the aluminum alloy ingot. Even if the heating time at the time of homogenization treatment exceeds 60 hours, the effect is saturated and no further remarkable improvement effect can be obtained.

  Next, in the case of DC cast aluminum alloy ingots, ingots which have been subjected to homogenization treatment or non-homogenization treatment as required are made into sheet materials by a hot rolling process (FIG. 1 (a Step S104)). The conditions for hot rolling are not particularly limited, but the hot rolling start temperature is preferably 250 to 600 ° C., and the hot rolling finish temperature is preferably 230 to 450 ° C.

  Next, a rolled sheet obtained by hot rolling an ingot cast by DC casting as described above, or a cast sheet cast by CC casting method is cold rolled to an aluminum alloy sheet of about 1.3 mm to 0.35 mm (Step S105). Finish the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, and may be determined according to the required product plate strength and plate thickness, and it is preferable to set the rolling reduction to 10 to 95%. Before cold rolling or in the middle of cold rolling, annealing may be performed to secure cold rolling workability. In the case of carrying out the annealing treatment, for example, in the case of batch type heating, it is preferable to carry out under conditions of 300 to 500 ° C. for 0.1 to 30 hours, and in the case of continuous type heating, 0 to 400 ° C. to 600 ° C. It is preferable to carry out under the condition of holding for 60 seconds. Here, the holding time of 0 seconds means cooling immediately after reaching the desired holding temperature.

  Next, a process of manufacturing the aluminum alloy plate manufactured as described above into a magnetic disk will be described. In order to process the aluminum alloy plate for a magnetic disk, the aluminum alloy plate is punched into an annular shape, and a disk blank is manufactured (step S106). Next, the disk blank is subjected to pressure annealing at, for example, 100 to 380 ° C. for 30 minutes or more in the atmosphere to prepare a flattened blank (step S107). Next, the blank is subjected to cutting, grinding, and preferably heat treatment for strain removal at a temperature of 250 to 400 ° C. for 5 to 15 minutes in this order to produce an aluminum alloy substrate (step S108). Next, after the surface of the aluminum alloy substrate is subjected to degreasing, acid etching, and desmutting, zincate (Zn substitution) is performed (step S109).

In the degreasing step, it is preferable to carry out degreasing under the conditions of a temperature of 40 to 70 ° C., a treatment time of 3 to 10 minutes, and a concentration of 200 to 800 mL / L using a commercially available AD-68F (manufactured by Kamimura Kogyo) degreasing solution or the like. In the acid etching process step, acid etching is performed at a temperature of 50 to 75 ° C., a treatment time of 0.5 to 5 minutes, and a concentration of 20 to 100 mL / L using a commercially available AD-107F (made by Kamimura Kogyo) etching solution or the like. Is preferred. In the case where the compound removal step has already been applied after the acid etching treatment, HNO ₃ is used as a normal desmutting treatment at a temperature of 15 to 40 ° C., a treatment time of 10 to 120 seconds, and a concentration of 10 to 60%. Desmutting is preferably performed. When the compound removal step is not applied, the above-mentioned compound removal treatment may be performed instead of or in addition to the desmutting treatment.

The 1st zincate treatment step is carried out under conditions of a temperature of 10 to 35 ° C., a treatment time of 0.1 to 5 minutes, and a concentration of 100 to 500 mL / L using a zincate treatment solution of AD-301F-3X (made by Kamimura Kogyo) commercially available. Is preferred. After the 1st zincate treatment step, it is preferable to perform Zn peeling treatment using HNO ₃ under conditions of a temperature of 15 to 40 ° C., a treatment time of 10 to 120 seconds, and a concentration of 10 to 60%. Thereafter, the 2nd zincate treatment step is carried out under the same conditions as the 1st zincate treatment.

  An electroless Ni-P plating process step is performed as a base plating process on the surface of the 2nd zincate-treated aluminum alloy substrate (S110 in FIGS. 1A and 1B). Electroless Ni-P plating treatment is carried out using a commercially available Nimden HDX (made by Uemura Kogyo) plating solution, etc., under conditions of temperature 80-95 ° C., treatment time 30-180 minutes, Ni concentration 3-10 g / L It is preferred to carry out the treatment. By such an electroless Ni-P plating process, an aluminum alloy substrate for a base plated magnetic disk can be obtained.

C. Magnetic disk Finally, the surface of the aluminum alloy base for the base plating treated magnetic disk is smoothed by polishing, and a magnetic medium consisting of a base layer, a magnetic layer, a protective film, a lubricating layer, etc. is attached to the surface by sputtering. (Step S111).

  In addition, after setting it as an aluminum alloy plate (S105), since there is no process which a structure | tissue changes like cold rolling, distribution and a component of a compound do not change. Therefore, instead of the aluminum alloy substrate (S108), an aluminum alloy plate (S105), a disk blank (step S106), an aluminum alloy substrate (step S110), a magnetic disk (step S111), etc. You may make an evaluation.

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

  An embodiment of the aluminum alloy substrate for a magnetic disk will be described. Each alloy raw material of the component composition shown to Tables 1-3 was fuse | melted according to a conventional method, and the aluminum alloy molten metal was melted (step S101). "-" In Tables 1-3 shows less than a measurement limit value.

  Next, under the conditions of Tables 4 to 6, No. Except for A40 to 42 and AC14, a molten aluminum alloy was cast by a DC method, an ingot with a thickness of 230 mm was produced, and both faces were surface-cut by 15 mm (step S102 in FIG. 1A). No. A40-42 and AC14 cast the aluminum alloy molten metal by CC method, and produced the cast plate of thickness 8 mm (step S102 of FIG.1 (b)). Next, No. Except A3-5, A40-42, and AC14, the homogenization heat processing for 2 hours was performed at 380 degreeC (step S103 of Fig.1 (a)). Next, except for A40 to 42 and AC14, hot rolling was performed at a hot rolling start temperature of 380 ° C. and a hot rolling finish temperature of 300 ° C. to obtain a hot-rolled sheet (step of FIG. 1A) S104).

  No. After hot rolling for the alloys A1 and A3, and after CC casting for the alloy A40, annealing (batch processing) was performed at 360 ° C. for 2 hours. The hot-rolled sheets of A1 to A39, A43 to A48, AC1 to AC13, AC15 and AC16, and CC cast sheets of A40 to A42 and AC14 prepared as described above have a final thickness of 0 by cold rolling. It rolled to .8 mm and was set as the aluminum alloy board (Step S105). An annular member having an outer diameter of 96 mm and an inner diameter of 24 mm was punched out of the aluminum alloy sheet to prepare a disk blank (step S106).

The disk blank thus produced was subjected to pressure flattening treatment at 270 ° C. for 3 hours under a pressure of 0.5 MPa (step S107). Next, end face processing was performed on the pressure-flattened disk blank to make the outer diameter 95 mm and the inner diameter 25 mm, and grinding (surface 50 μm grinding) was performed to produce an aluminum alloy substrate (step S108). After degreasing at 60 ° C. for 5 minutes with AD-68F (trade name, manufactured by Kamimura Kogyo), acid etching is then performed at 65 ° C. for 1 minute by AD-107F (trade name, manufactured by Kamimura Kogyo), and further It was desmutted with a 30% aqueous HNO ₃ solution (room temperature) for 20 seconds (step S109).

After adjusting the surface condition in this manner, the disk blank was dipped in an AD-301F-3X (trade name, manufactured by Kamimura Kogyo Co., Ltd.) zincate treatment solution at 20 ° C. for 0.5 minutes to subject the surface to zincate treatment ( Step S109). The zincate treatment was performed twice in total, and the surface was peeled off by being immersed in a 30% aqueous solution of HNO ₃ at room temperature for 20 seconds during the zincate treatment. After electroless plating Ni-P to 11.5μm thickness using electroless Ni-P plating solution (Nimden HDX (trade name, manufactured by Uemura Kogyo)) on the zincate-treated surface, finish polishing with feather cloth ( The polishing amount is 1.5 μm)) to form an aluminum alloy substrate for a magnetic disk substrate disk (step S110).

  Aluminum alloy plate after cold rolling (step S105), disk blank after pressure flattening process (step S107) process, aluminum alloy substrate after grinding process (step S108) process, and plating process polishing (step S110) The following evaluation was performed on the aluminum alloy base after the process. In addition, although the plating process was implemented to three discs about each sample, in the disc of Comparative Examples 4-12, since plating peeling had arisen by all three sheets, measurement of disc flutter was carried out in these comparative examples. Could not do.

[Distributed density of Al-Zr based intermetallic compound having longest diameter of 1 μm or more]
The surface of the aluminum alloy substrate after grinding (step S108) is polished by 10 μm, and the compound is analyzed at the same time by SEM with a magnification of 1000 times, and the distribution of Al-Zr based intermetallic compounds having a longest diameter of 1 μm or more The density was calculated. Incidentally, shooting, total performed for a plurality of the field of view as a 1.0 mm ^2, and the distribution density by summing the number in each field.

[Measurement of disk flutter]
Disk flutter was measured using the aluminum alloy substrate after the plating treatment and polishing (step S110) step. Disk flutter was measured by installing an aluminum alloy base in the presence of air on a commercially available hard disk drive. The drive was driven by using Seagate ST2000 (trade name), and the motor was driven by directly connecting Techno Alive SLD 102 (trade name) to the motor. The rotational speed was 7200 rpm, and a plurality of disks were always installed, and the vibration of the surface was observed on the surface of the upper magnetic disk by Ono Sokki LV1800 (trade name) which is a laser Doppler meter. The observed vibration was spectrally analyzed by Ono Sokki FFT analyzer DS3200 (trade name). The observation was made by observing the disk surface from the hole by making a hole in the lid of the hard disk drive. Moreover, the squeeze plate installed in the commercially available hard disk was removed for evaluation.

  The fluttering characteristics were evaluated by the maximum displacement of the broad peak (disk fluttering (nm)) around 300 to 1500 Hz where the fluttering appeared. This broad peak is called NRRO (Non-Repeatable Run Out) and has been found to have a significant effect on head positioning error. Evaluation of fluttering characteristics is as follows: in the air, if A is 30 nm or less, A (excellent), more than 30 nm to 40 nm or less B (good), greater than 40 nm to 50 nm or less C (acceptable), larger than 50 nm Was D (less).

[Force resistance]
With regard to the proof stress, according to JIS Z 2241, after annealing (pressure annealing simulation heating) for 3 hours at 280 ° C., the aluminum alloy plate after cold rolling (step S105) is heated in the atmosphere for 3 hours at 270 ° C. Conducted, JIS No. 5 test pieces were collected along the rolling direction and measured at n = 2. As for evaluation of strength, when the yield strength is 100 MPa or more, A (excellent), 90 MPa or more and less than 100 MPa is B (good), 80 MPa or more and less than 90 MPa is C (good), and less than 80 MPa is D (poor).

  It is also possible to peel off the plating of the aluminum alloy substrate or magnetic disk after grinding processing, extract a test piece from the substrate whose surface is ground by 10 μm, heat it in the air at 270 ° C for 3 hours, and evaluate the proof stress. It is. The dimensions of the test piece at this time are: width of the parallel part 5 ± 0.14 mm, original standard distance of the test piece 10 mm, radius of the shoulder 2.5 mm, and length of the parallel part 15 mm.

  The above evaluation results are shown in Tables 7-9.

  As shown in Tables 7 and 8, in Examples 1 to 48, the distribution density of the intermetallic compound satisfied the range specified in the present invention, and it was possible to obtain good fluttering characteristics and strength.

  On the other hand, in Comparative Example 1, the fluttering characteristics and the strength were inferior because the Fe content of the aluminum alloy was too low.

  In Comparative Example 2, the strength was inferior because Zr of the aluminum alloy was not contained.

  In Comparative Example 3, since the Fe content of the aluminum alloy was too low and Zr was not contained, the fluttering characteristics and the strength were inferior.

  In Comparative Example 4, since the Fe content of the aluminum alloy was too large, plating peeling occurred as described above, and the fluttering characteristics could not be evaluated, so that it was unsuitable as a magnetic disk.

  In Comparative Example 5, since the Zr content of the aluminum alloy was too large, the plating peeling occurred as described above, the fluttering characteristics could not be evaluated, and the magnetic disk was unsuitable as a magnetic disk. In addition, the distribution density of the Al-Zr based intermetallic compound was too large.

  In Comparative Example 6, since the Mn content of the aluminum alloy was too large, plating peeling occurred as described above, and the fluttering characteristics could not be evaluated, so that it was not suitable as a magnetic disk.

  In Comparative Example 7, the plating peeling occurred as described above because the Si content of the aluminum alloy was too large, and the fluttering characteristics could not be evaluated, which was unsuitable as a magnetic disk.

  In Comparative Example 8, since the aluminum content of the aluminum alloy was too large, plating peeling occurred as described above, and the fluttering characteristics could not be evaluated, which was unsuitable as a magnetic disk.

  In Comparative Example 9, since the Cu content of the aluminum alloy was too large, plating peeling occurred as described above, and the fluttering characteristics could not be evaluated, so that it was not suitable as a magnetic disk.

  In Comparative Example 10, the plating peeling occurred as described above because the Mg content of the aluminum alloy was too large, and the fluttering characteristics could not be evaluated, which was unsuitable as a magnetic disk.

  In Comparative Example 11, the plating peeling occurred as described above because the Cr content of the aluminum alloy was too large, and the fluttering characteristics could not be evaluated, which was unsuitable as a magnetic disk.

  In Comparative Example 12, the plating peeling occurred as described above because the Zn content of the aluminum alloy was too large, and the fluttering characteristics could not be evaluated, which was unsuitable as a magnetic disk.

  In Comparative Examples 13 to 16, since the molten metal holding time in the temperature range of 660 to 680 ° C. was too long, many Al-Zr based intermetallic compounds having the longest diameter of 1 μm or more were generated, and the strength was inferior.

  According to the present invention, an aluminum alloy substrate for a magnetic disk having good fluttering characteristics and strength, a method of manufacturing the same, and a magnetic disk using the same can be obtained.

Claims (11)

Fe--0.05 to 3.00 mass%, Zr: 0.01 to 0.50 mass%, and it consists of an aluminum alloy consisting of the balance Al and unavoidable impurities, and has an longest diameter of 1 μm or more. An aluminum alloy substrate for a magnetic disk, wherein a distribution density of the compound is 1 piece / mm ² or less.   The said aluminum alloy is Mn: 0.1-3.0 mass%, Si: 0.1-0.4 mass%, Mg: 0.1-0.4 mass%, Cu: 0.005-0.500 mass%, Ni The aluminum alloy substrate for a magnetic disk according to claim 1, further comprising one or more selected from the group consisting of: 0.1 to 3.0 mass% and Cr: 0.01 to 1.00 mass%. .   The aluminum alloy substrate for a magnetic disk according to claim 1 or 2, wherein the aluminum alloy further contains Zn: 0.005 to 1.000 mass.   The said aluminum alloy further contains 1 type, or 2 or more types selected from the group which consists of Ti, B, and V whose sum total of content is 0.005-0.500 mass%. The aluminum alloy substrate for a magnetic disk according to any one of the above.   A magnetic disk characterized in that an electroless Ni-P plated layer and a magnetic layer thereon are provided on the surface of the aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4. .   A method for manufacturing an aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4, comprising: a semicontinuous casting step of casting an ingot by a semicontinuous casting method using the aluminum alloy; Hot rolling process of hot rolling continuously cast ingot, cold rolling process of cold rolling hot rolled sheet, disc blank punching process of stamping cold rolled sheet in annular shape, stamped disc blank And a cutting / grinding step of cutting and grinding the disk blank subjected to pressure annealing, and in the casting step, the molten metal holding time in the temperature range of 660 to 680 ° C. A method of manufacturing an aluminum alloy substrate for a magnetic disk, wherein the time is 5 minutes or less.   The magnetic treatment process according to claim 6, further comprising a homogenizing heat treatment step of heat treating the semicontinuously cast ingot at 280 to 620 ° C. for 0.5 to 60 hours between the semi continuous casting step and the hot rolling step. Method of manufacturing aluminum alloy substrate for disc.   The method for manufacturing an aluminum alloy substrate for a magnetic disk according to claim 6 or 7, wherein the start temperature of the hot rolling step is 250 to 600 ° C and the end temperature is 230 to 450 ° C.   Before or during the cold rolling, it is an annealing treatment step of annealing a rolled sheet, and is a batch annealing treatment step at 300 to 500 ° C. for 0.1 to 30 hours, or at 400 to 600 ° C. for 0 to 60 seconds The method for producing an aluminum alloy substrate for a magnetic disk according to any one of claims 6 to 8, further comprising a continuous annealing treatment step.   A method of manufacturing an aluminum alloy substrate for a magnetic disk according to any one of claims 1 to 4, wherein the continuous casting step of casting a cast plate by a continuous casting method using the aluminum alloy, and continuous casting A cold rolling step of cold rolling a cast plate, a disk blank punching step of punching the cold rolled plate into an annular shape, a pressure annealing step of pressure annealing the punched disk blank, and a pressure annealed disk blank An aluminum alloy substrate for a magnetic disk, characterized by including a cutting and grinding step of cutting and grinding, wherein the molten metal holding time in the temperature range of 660 to 680 ° C. is 5 minutes or less in the casting step. Production method.   Before or during the cold rolling, it is an annealing treatment step of annealing a cast plate or a cold rolled plate, and is a batch annealing treatment step at 300 to 500 ° C. for 0.1 to 30 hours, or at 400 to 600 ° C. The method of manufacturing an aluminum alloy substrate for a magnetic disk according to claim 10, further comprising a continuous annealing process step of 0 to 60 seconds.

Images