JP2020153012A - Aluminum alloy blank for magnetic disk, and aluminum alloy substrate for magnetic disk - Google Patents

Abstract

To provide an aluminum alloy blank for a magnetic disk and an aluminum alloy substrate for a magnetic disk having a high attenuation factor.SOLUTION: An aluminum alloy blank for a magnetic disk and an aluminum alloy substrate for a magnetic disk of the invention are composed of Mn of 1.00 mass% or more and 10 mass% or less and the balance Al and inevitable impurities. There is an intermetallic compound of a maximum length of 0.2-15.0 μm of which the number density is 1.5×105/mm2 or more on the surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to an aluminum alloy blank for a magnetic disk and an aluminum alloy substrate for a magnetic disk.

With the digitization of information and the spread of the Internet, a large amount of digital data will be handled, and there is a demand for increasing the capacity of hard disk drives (HDD) mainly in data centers. Then, in order to increase the capacity of the HDD and to increase the number of magnetic disks mounted on each HDD, thinning of the magnetic disk is being studied.
Then, in the study of thinning the magnetic disk, it is proposed to reduce the thickness of the magnetic disk mounted on the 3.5-inch HDD from the conventional 1.3 mm to 0.8 mm or less. ..

However, when the magnetic disk is rotationally driven, the probability of occurrence of minute vibrations increases as the magnetic disk becomes thinner, especially in a state of being stabilized at a high rotation speed (for example, 7200 rpm or more).

The following techniques have been proposed for materials for such magnetic disks.
For example, Patent Document 1 describes second-phase particles containing Fe: 0.4 to 3.0 mass%, made of an aluminum alloy composed of the balance Al and unavoidable impurities, and having the longest diameter of 3 μm or more in a metal structure. An aluminum alloy substrate for a magnetic disk is disclosed, which has a peripheral length of 10 mm / mm ² or more.

Japanese Patent No. 6437583

In order to suppress the vibration caused by the thinning of the magnetic disk, the present inventors have carried out diligent research on a material for a magnetic disk having an excellent property of attenuating the vibration, in other words, a material having a high damping factor.

Here, according to the above-mentioned Patent Document 1, it is explained that the disc fluttering characteristic of the aluminum alloy substrate for a magnetic disk becomes excellent by adding a predetermined amount of Fe.
However, the present inventors have confirmed that the addition of Fe cannot sufficiently improve the damping rate. Further, as a technique for suppressing vibration of a magnetic disk, it is required to create a new technique having characteristics different from the technique described in Patent Document 1.

Therefore, it is an object of the present invention to provide an aluminum alloy blank for a magnetic disk and an aluminum alloy substrate for a magnetic disk having a high attenuation rate.

The aluminum alloy blank for magnetic disks and the aluminum alloy substrate for magnetic disks according to the present invention have Mn: 1.00% by mass or more and 10% by mass or less, and the balance is composed of Al and unavoidable impurities, and has a maximum length on the surface. The number density of the intermetallic compound having a value of 0.2 to 15.0 μm is 1.5 × 10 ⁵ / mm ² or more.

Further, the aluminum alloy blank for a magnetic disk and the aluminum alloy substrate for a magnetic disk according to the present invention include a core material and a skin material provided on at least one surface of the core material, and the core material is Mn: 1. Of 00 mass% or more and 10 mass% or less, Mg: 3.0 mass% or less, Cr: 0.5 mass% or less, Zn: 0.4 mass% or less, Cu: 0.4 mass% or less. The number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface of the core material is 1.5 × 10 ⁵ pieces / mm ² which contains at least one kind and the balance is composed of Al and unavoidable impurities. That is all.

According to such a configuration, the aluminum alloy blank for a magnetic disk and the aluminum alloy substrate for a magnetic disk have high internal friction and can exhibit a high damping rate.

The aluminum alloy blank for magnetic disks and the aluminum alloy substrate for magnetic disks according to the present invention can exhibit a high damping factor.

6 is a graph showing the relationship between the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm and internal friction.

Hereinafter, embodiments for carrying out the aluminum alloy blank for magnetic disks (hereinafter, also simply referred to as blank) and the aluminum alloy substrate for magnetic disks (hereinafter, also simply referred to as substrate) according to the present invention will be described in detail.

[blank]
The blank according to the present embodiment contains Mn within a predetermined range, and the balance is Al and unavoidable impurities.
The blank according to the present embodiment has a number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface (hereinafter, appropriately referred to as “intermetallic compounds of a predetermined size”) of a predetermined value or more. ..
Hereinafter, each configuration will be described in detail.

(Mn: 1.00% by mass or more and 10% by mass or less)
Mn not only contributes to the improvement of strength and proof stress, but also contributes to the improvement of the property of damping vibration (improvement of damping rate). If the Mn content is less than 1.00% by mass, the number density of the intermetallic compounds of a predetermined size becomes small, and as a result, the internal friction does not become sufficiently high, and the damping factor is sufficiently improved. Can not do it. On the other hand, if the Mn content exceeds 10% by mass, the grindability (easiness of grinding) may be lowered, and the intermetallic compound becomes coarse, so that the number density of the intermetallic compound of a predetermined size becomes high. There is a risk that it will become smaller.
Therefore, the Mn content is 1.00% by mass or more and 10% by mass or less.

The Mn content is preferably 1.50% by mass or more, preferably 1.80% by mass or more, 2.00% by mass or more, 2.50% by mass or more, and 3.00% by mass or more from the viewpoint of improving the damping rate. More preferred. The Mn content is preferably 8.00% by mass or less, more preferably 5.00% by mass or less, and still more preferably 4.00% by mass or less, from the viewpoint of grindability and prevention of coarsening of intermetallic compounds.

(Fe: 0.30% by mass or less)
Fe contributes to the improvement of strength and Young's modulus. However, Fe cannot be expected to have a sufficiently improved attenuation rate as compared with Mn, and when the Fe content exceeds 0.30% by mass, the intermetallic compound becomes coarse, resulting in a predetermined size. The number density of the intermetallic compound becomes small, and the attenuation rate may decrease.
Therefore, although Fe is not an essential component, when Fe is contained, the Fe content is 0.30% by mass or less. The Fe content is preferably 0.25% by mass or less, preferably 0.20% by mass or less, 0.10% by mass or less, 0.05% by mass or less, and 0.04 from the viewpoint of preventing the intermetallic compound from coarsening. More preferably, it is by mass or less.
When Fe is contained as an unavoidable impurity, the content of Fe is preferably 0.05% by mass or less, more preferably 0.03% by mass or less. Since Fe is mixed in the bare metal as an unavoidable impurity, it is necessary to use a high-purity bare metal in order to reduce the content, resulting in high cost. Therefore, when Fe is contained as an unavoidable impurity, the content of Fe is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, from the viewpoint of cost.

(The rest is Al and unavoidable impurities)
The basic composition of the chemical composition constituting the blank according to the present embodiment is as described above, and the balance is Al and unavoidable impurities. The unavoidable impurities are impurities that are inevitably mixed in when the raw material is dissolved, and are contained within a range that does not impair various characteristics of the blank. Examples of unavoidable impurities include Ni, Ti, Na, Pb, Be, Ca, Zr, V, B, Sn, In, Cd, Bi, Ge and the like.
These unavoidable impurities do not inhibit the effect of the present invention if they are 0.005% by mass or less individually and 0.015% by mass or less in total. Therefore, in the present invention, unavoidable impurities may be contained within a range that does not inhibit the effect of the present invention, and even when they are positively added within a range that does not inhibit the effect of the present invention. It does not interfere with the effects of the present invention. That is, these aspects are also included in the technical scope of the present invention.

The chemical composition of the blank according to the present embodiment can be obtained, for example, by appropriately adjusting the amount of the element added when melting the Al alloy. Further, the content of unavoidable impurities can be adjusted (regulated), for example, by using a bare metal refined by a three-layer electrolysis method or by eliminating these by using a segregation method.

(Number of intermetallic compounds with a maximum length of 0.2 to 15.0 μm Density: 1.5 × 10 ⁵ / mm ² or more)
As a result of diligent studies on the blanks having the above-mentioned chemical composition, the present inventors have found that fine intermetallic compounds having a maximum surface length of less than 0.2 μm and coarse intermetallic compounds having a maximum length of more than 15.0 μm have internal friction. It was found that there is a strong positive correlation between "the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface" and "internal friction", while not having a large effect on It was.
Specifically, when the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface of the blank is 1.5 × 10 ⁵ / mm ² or more, the internal friction shows a sufficiently high value. That is, a sufficiently high attenuation rate can be exhibited.
Therefore, the number density of the intermetallic compound of the maximum length is 0.2~15.0μm is 1.5 × 10 ⁵ cells / mm ² or more. The number density of the intermetallic compound of a predetermined size is preferably 2.0 × 10 ⁵ pieces / mm ² or more, 2.5 × 10 ⁵ pieces / mm ² or more, 3.0 × from the viewpoint of improving internal friction. 10 ⁵ pieces / mm ² or more, 3.3 × 10 ⁵ pieces / mm ² or more, 3.4 × 10 ⁵ pieces / mm ² or more is more preferable.
Although the upper limit of the number density of intermetallic compounds of a predetermined size is not particularly limited, for example, 20.0 × 10 ⁵ pieces / mm ² or less, 10.0 × 10 ⁵ pieces / mm ² or less, 8.0 × 10 ⁵ pieces / mm ² or less, 5.0 × 10 ⁵ pieces / mm ² or less.

The number density of intermetallic compounds of a predetermined size on the blank surface can be controlled by the Mn content, the molten metal temperature, and the conditions of the homogenization heat treatment. The same applies to the number density of intermetallic compounds of a predetermined size on the surface of the substrate, which will be described later.
Then, the number density of the intermetallic compound of a predetermined size on the blank surface can be measured by using a scanning electron microscope (SEM) after making the surface a mirror surface.

(Internal friction: 1.50 x 10 ^-3 or more)
The internal friction of the blank according to this embodiment is preferably 1.50 × 10 ^-3 or more. When the internal friction of the blank is 1.50 × 10 ^-3 or more, the vibration of the magnetic disk generated during the rotational drive can be suppressed by the internal friction of the material, so that the property of damping the vibration is improved (damping factor). The effect of (improvement) can be made more certain.
The internal friction is preferably 1.60 × 10 ^-3 or more, more preferably 1.70 × 10 ^-3 or more, and 1.80 × 10 ^-3 or more, from the viewpoint of improving the damping rate.
Although the upper limit of internal friction is not particularly limited, for example, 5.00 × 10 ^-3 or less, 4.00 × 10 ^-3 or less, 3.00 × 10 ^-3 or less, 2.50 × 10 ^-3 or less, It is 2.00 x 10 ^-3 or less.

The internal friction of the blank can be controlled by the Mn content, the molten metal temperature, and the conditions of the homogenization heat treatment, as well as the number density of the intermetallic compounds of a predetermined size. The same applies to the internal friction of the substrate, which will be described later.
Then, the internal friction of the blank can be measured by using an internal friction measuring device based on the half width method.

(Proof stress)
The proof stress of the blank according to the present embodiment is not particularly limited, but from the viewpoint of improving the impact resistance, for example, 150 MPa or more is preferable, and 155 MPa or more and 160 MPa or more are more preferable. The upper limit of the proof stress is not particularly limited, but is, for example, 220 MPa or less and 200 MPa or less.

The yield strength of the blank can be controlled by the Mn content. The same applies to the proof stress of the substrate, which will be described later.
The proof stress of the blank can be determined, for example, by preparing a test piece from the blank in accordance with JIS Z 2241: 2011 and performing a metal material tensile test.

[substrate]
The substrate according to the present embodiment is manufactured by cutting the end face of the blank according to the above-described embodiment (end face processing) and grinding the surface (main surface) (mirror surface processing).
The substrate may also be referred to as a grind substrate.

The substrate according to this embodiment has the same chemical composition and composition as the blank according to this embodiment described above. Therefore, when the substrate according to the present embodiment is applied to the magnetic disk, it is possible to suppress minute vibrations in the vertical direction (rotational axis direction) generated when the magnetic disk is rotationally driven, even when the thickness is thinned. ..
The numerical ranges relating to the chemical composition of the substrate, the number density of intermetallic compounds of a predetermined size, the internal friction, and the proof stress are the same as in the case of the blank described above.

[Blank manufacturing method]
Next, an example of a blank manufacturing method according to the present embodiment will be described.
The blank according to the present embodiment can be manufactured by a manufacturing method and equipment under the general conditions for manufacturing a blank for a magnetic disk, except for some conditions. For example, a casting step of melting raw materials and casting a molten metal adjusted to a predetermined chemical composition into an ingot, a homogenizing heat treatment step of subjecting the cast ingot to a homogenizing heat treatment, and a homogenizing heat treatment are performed. It is obtained by a hot rolling step of hot rolling an ingot to obtain a hot rolled plate, a cold rolling step of cold rolling a hot rolled plate to obtain a cold rolled plate, and cold rolling. A blank can be manufactured by a manufacturing method including a punching step of punching an aluminum alloy plate in an annular shape and a straightening and annealing step of performing straightening and annealing on the punched substrate in this order. If necessary, intermediate annealing may be performed before the cold rolling step or during the cold rolling step.
Hereinafter, each step will be described in detail.

(Casting process)
In the casting process, the raw material is melted at 700 to 800 ° C. and cast by a known casting method. Further, the cast ingot is preferably face-cut, and the face-cut amount may be, for example, 2 to 40 mm / one side.
The molten metal temperature (the molten metal temperature at the time of injection into the mold) is generally about 670 ° C., but by setting it to 680 ° C. or higher, precipitation of coarse crystals is avoided, and finally a predetermined size is obtained. The number density of intermetallic compounds can be increased.
Further, the molten metal temperature is preferably 690 ° C. or higher, more preferably 700 ° C. or higher, from the viewpoint of avoiding precipitation of coarse crystals.
When melting the Al alloy, it is preferable to blow an inert gas such as argon (Ar) into the molten metal to perform dehydrogenation treatment. The casting speed is preferably 30 to 80 mm / min.

(Asymptotic heat treatment process)
In the homogenization heat treatment step, for example, homogenization heat treatment is performed at 430 to 620 ° C. for 2 hours or more. When the homogenization heat treatment is performed under such conditions, the intermetallic compound can be sufficiently dissolved. If the temperature of the homogenization heat treatment is less than 430 ° C. or the time of the homogenization heat treatment is less than 2 hours, the intermetallic compound is coarsened and the intermetallic compound of a predetermined size is reduced. On the other hand, if the temperature of the homogenization heat treatment exceeds 620 ° C., the surface of the ingot melts.
The temperature of the homogenization heat treatment is preferably 480 ° C. or higher, more preferably 510 ° C. or higher, from the viewpoint of increasing the number density of intermetallic compounds of a predetermined size, and from the viewpoint of suppressing melting of the ingot surface. It is preferably 600 ° C. or lower, more preferably 580 ° C. or lower. Further, the time of the homogenization heat treatment may be, for example, 25 hours or less and 20 hours or less from the viewpoint of production efficiency.

Then, in the homogenization heat treatment step, when the homogenization heat treatment is performed in the low temperature region of 400 to 470 ° C. in the first stage and in the high temperature region of more than 470 ° C. and less than 630 ° C. in the second stage (for example, in Patent No. 6316511). The method described), the intermetallic compound precipitates or the crystallized product size grows and coarsens in the first stage, so that the intermetallic compound of a predetermined size does not precipitate in the second stage, and finally the predetermined size. The number density of intermetallic compounds in the above becomes small.
Therefore, in the homogenization heat treatment step, one homogenization heat treatment is preferable.

(Hot rolling process)
In the hot rolling step, for example, the starting temperature of hot rolling can be set to 490 ° C. or higher. Further, the end temperature of hot rolling can be set to 300 to 350 ° C. The hot rolling from 520 ° C. to 400 ° C. is preferably completed within 30 minutes, more preferably within 15 minutes. Further, the plate thickness of the hot-rolled plate obtained by hot-rolling can be, for example, 5 mm or less and 3 mm or less.

(Cold rolling process)
In the cold rolling step, cold rolling is performed so as to achieve the target blank plate thickness. Specific examples of the plate thickness include 0.5 to 1.3 mm. If necessary, intermediate annealing may be performed before cold rolling or during cold rolling.

(Punching process)
In the punching process, the cold-rolled plate material is tempered as necessary, and then an aluminum alloy plate is applied so that it can be applied to, for example, a substrate for a 3.5-inch HDD and a substrate for a 2.5-inch HDD. Punch into the desired shape.

(Correcting annealing process)
In the straightening and annealing step, the substrates are sandwiched between spacers having high flatness and stacked, and the substrates are annealed while applying a load. The annealing temperature can be 250 to 500 ° C. (preferably 300 to 400 ° C.), and the holding time can be, for example, about 4 to 5 hours or 3 hours. The rate of temperature rise in straightening annealing is, for example, 80 ° C./hour (Max.150 ° C./hour) on average, and the temperature can be lowered (cooled) by opening the door of the annealing furnace, for example.

As described above, the main difference between the blank and the substrate in this embodiment is whether or not grinding (mirror surface processing) is performed. Therefore, the measurement result of the internal friction of the blank, the measurement result of the intermetallic compound, and the measurement result of the proof stress can be regarded as the measurement result of the substrate as it is, and vice versa.

[Manufacturing method of substrate]
The substrate according to the present embodiment is sub-straightened by, for example, a manufacturing method in which a cutting process (end face processing) for cutting the end face of the blank and a grinding process (mirror surface processing) for grinding the surface (main surface) of the blank are performed. A straight can be manufactured.

[Magnetic disk and its manufacturing method]
In the method of manufacturing a magnetic disk, first, the surface of the substrate is acid-etched to form an electroless Ni-P plating film, and then the surface is polished (note that the sub having an electroless Ni-P plating film formed). Straights are sometimes referred to as plated substrate). Next, on the surface of this substrate, a base film for enhancing magnetic properties, a magnetic film made of a Co-based alloy, a protective film made of C (carbon) for protecting the magnetic film, and the like are formed by sputtering or the like. This makes it possible to manufacture a magnetic disk.
The electroless Ni-P plating film, the undercoat film, the magnetic film, and the protective film can be formed under the conditions generally used in manufacturing a magnetic disk.

In manufacturing the blank and the substrate, for example, the manufacturing conditions described in Japanese Patent No. 3471557 and Japanese Patent No. 5199714 can be referred to.

The magnetic disk manufactured in this manner has a thickness of 0.5 to 1.3 mm. Further, this magnetic disk can be applied to a 3.5-inch HDD and a 2.5-inch HDD.

(Other processes)
The method for manufacturing the blank, the substrate, and the magnetic disk according to the present embodiment is as described above, but other methods may be used during, before, or after each of the steps as long as the steps are not adversely affected. The process may be included.

[Another Embodiment]
Although the embodiment in which the present invention is applied to a single-layer material has been described so far, the present invention is applied to a laminated material including a "core material" and a "skin material" provided on at least one surface of the core material. You can also do it.

[Blank and substrate (separate embodiment)]
The blank and substrate according to another embodiment are composed of a laminated material including a "core material" and a "skin material" provided on at least one surface of the core material.
When the blank and the substrate are laminated materials, it is preferable that the laminated material as a whole satisfies the above-mentioned "proof stress" requirement and "internal friction" requirement of the single layer material.

(Heartwood)
The blank and substrate core materials according to another embodiment are required to have "composition of each component" and "number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface" of the above-mentioned single layer material. It is preferable to satisfy.
Further, in the blank and substrate core materials according to another embodiment, from the viewpoint of rollability and recyclability, in addition to the above-mentioned "composition of each component" of the single layer material, Mg: 3.0% by mass or less (preferably). Is 1.5% by mass or less), Cr: 0.5% by mass or less (preferably 0.25% by mass or less), Zn: 0.4% by mass or less (preferably 0.2% by mass or less), Cu: 0 It may further contain at least one of 0.4% by mass or less (preferably 0.10% by mass or less).

(Skin material)
The skin material of the blank and the substrate according to another embodiment is not particularly limited, and examples thereof include those made of Al-Mg-based materials such as A5086 specified in JIS H 4000: 2014.
Specifically, the skin material is Mg: 1.8% by mass or more and 7.0% by mass or less, Cr: 0.01% by mass or more and 0.35% by mass or less, Si: 0.1% by mass or less, Fe: It contains at least one of Cu: 0.1% by mass or less and Zn: 0.4% by mass or less, and the balance is composed of Al and unavoidable impurities.

(Remaining skin material: Al and unavoidable impurities)
The remaining components of the skin material of the blank and the substrate according to another embodiment are Al and unavoidable impurities. Examples of unavoidable impurities include Mn, Ti, V, Zr, Ni, Na, Be, Ca, Pb, B, Sn, In, Cd, Bi, Ge and the like. Further, the above-mentioned Si, Fe, Cu and Zn may also be contained as unavoidable impurities.
These unavoidable impurities do not inhibit the effect of the present invention if they are 0.005% by mass or less individually and 0.015% by mass or less in total. Therefore, in the present invention, unavoidable impurities may be contained within a range that does not inhibit the effect of the present invention, and even when they are positively added within a range that does not inhibit the effect of the present invention. It does not interfere with the effectiveness of the invention (ie, these aspects are also within the technical scope of the invention).

(Clad rate, etc.)
The thickness of the blank and the substrate according to another embodiment is not particularly limited, but may be 0.5 to 1.3 mm as in the case of the single layer material. Further, the clad ratio of the skin material (the ratio of the thickness of each skin material when the thickness of the laminated material is 100%) in the blank and the substrate according to another embodiment is 3 to 50%, preferably 5 to 5%. It may be 30%.

[Blank manufacturing method (separate embodiment)]
The blank according to another embodiment can be manufactured by the manufacturing method and equipment under the general conditions for manufacturing a substrate for a magnetic disk, except for some conditions, in the case of a laminated material as in the case of a single-layer material. it can.

For example, for a core material, a casting step of melting an Al alloy having the above-mentioned chemical composition and casting an ingot adjusted to the above-mentioned chemical composition and a homogenization heat treatment step of subjecting the cast ingot to a homogenization heat treatment are performed. , The core material is manufactured by a manufacturing method including this order.
As for the skin material, a casting step of melting the Al alloy having the above-mentioned chemical composition and casting an ingot adjusted to the above-mentioned chemical composition, and a homogenization heat treatment step of subjecting the cast ingot to a homogenization heat treatment. The skin material is manufactured by a manufacturing method including a hot rolling step of hot rolling an ingot that has undergone homogenization heat treatment to obtain a hot rolled plate in this order.

After manufacturing the core material and the skin material, they are laminated, a homogenizing heat treatment step of applying a homogenizing heat treatment to the laminated material, a hot rolling process of hot rolling the laminated material, and a laminated material. A cold rolling step of rolling to a desired thickness, a punching step of punching a laminated material obtained by cold rolling in an annular shape, and a straightening annealing step of performing straightening annealing on the punched laminated material are included in this order. A blank (laminated material) can be manufactured depending on the manufacturing method.
The conditions in each step are as follows.

In the core material casting step and homogenization heat treatment step, in order to control the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface, the above-mentioned single-layer material “casting step” and “homogeneity” are performed. It is carried out so as to satisfy the conditions shown in "Casting heat treatment step".
The skin material casting step, homogenization heat treatment step, and hot rolling step are carried out so as to satisfy the conditions shown in the above-mentioned "casting step", "homogenization heat treatment step", and "heat treatment step" of the single-layer material. do it.

Examples of the superposition method in the superposition step include a conventionally known method, for example, a method of hanging a band on both ends of a core material and a leather material, a method of welding and fixing the material, and the like.
The homogenization heat treatment for the laminated material may be carried out under the conditions of, for example, 500 to 550 ° C. and 1 to 20 hours.
The hot rolling of the laminated material may be carried out under the conditions that the starting temperature is 510 to 540 ° C. and the time from the end of the homogenization heat treatment to the end of the hot rolling is within 30 minutes.
Cold rolling on the laminated material may be carried out, for example, so that the plate thickness is 0.5 to 1.3 mm.
The punching step for the laminated material may be carried out so as to satisfy the conditions shown in the "punching step" for the single-layer material described above. Further, the straightening annealing step for the laminated material may also be carried out so as to satisfy the conditions shown in the above-mentioned "straightening annealing step" for the single-layer material, but the holding time is set as long as 7 to 9 hours. You may.

The slice milling method described in paragraph 0048 of Japanese Patent No. 5271094 may be applied to the respective manufacturing methods of the core material and the skin material. Specifically, the ingots obtained by melting and casting the Al alloy for the core material and the Al alloy for the skin material are face-cut and homogenized heat-treated, respectively, and the ingot for the skin material and the ingot for the core material are subjected to surface grinding and homogenization heat treatment, respectively. (Heartwood) is manufactured. Then, the ingot for the skin material is further face-cut and homogenized heat-treated, and then sliced to a desired thickness for production. In this case, it is necessary to appropriately control the homogenization heat treatment conditions and the hot rolling conditions after the superposition step so as to satisfy the conditions shown in the above-mentioned single layer material.

The method of manufacturing a substrate or a magnetic disk using a blank (laminated material) is the same as that of a single-layer material.

Hereinafter, the present invention will be specifically described with reference to examples of the present invention. However, the technical scope of the present invention is not limited to this.

[Example 1: Single layer material]
[Preparation of test materials]
First, the material was melted, and the molten metal whose components were adjusted so as to have the chemical composition shown in Table 1 was injected into a mold having a thickness of 50 mm, a width of 145 mm, and a length of 200 mm to prepare a slab. The molten metal temperature (the molten metal temperature at the time of injection into the mold) was about 720 ° C. Then, both sides (thickness direction) of the obtained slab were face-cut by 2 mm. Then, one homogenization heat treatment was performed at the temperature and time shown in the table. Then, hot rolling (starting temperature: about 510 ° C.) was performed until the thickness became 5 mm, and then cold rolling (material temperature did not exceed 100 ° C.) was performed until the thickness became 0.7 mm. ..
Then, this cold-rolled plate was punched into a ring shape of 3.5 inch size (outer diameter of about 95 mm, inner diameter of about 25 mm), stacked, and subjected to straightening annealing. Straightening annealing was performed by holding at 350 ° C. for 3 hours.

Then, it was peeled off to manufacture a blank (plate thickness 0.7 mm) for a 3.5-inch HDD. Next, the end face of each blank was processed. Then, the blank surface (both sides) was ground with a PVA grindstone (No. 4000 manufactured by Nippon Tokushu Kento Co., Ltd.) by 10 μm on one side (mirror surface processing) to produce a substrate (plate thickness 0.7 mm).

Using the manufactured blank or substrate, the number density, internal friction, and proof stress (reference) of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface were measured.
These measurements were made as follows.

[Measuring method]
(1) Number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm The surface of the blank is cut with a diamond bite to make a mirror surface, and this surface is FE-SEM (JSM-7001F, manufactured by JEOL Ltd.). Using the built-in particle analysis software EX-35110 and particle analysis software Ver.3.84: Ver. Information described in the release notes, acceleration voltage 15 kV), 10 fields (1 field: 60 μm x 45 μm) were photographed at a magnification of 2000 times. Then, a COMPO image (composition image) was obtained. Then, the COMPO image is analyzed with Image-Pro PLUS J Version 6.1.0.372, the threshold value is set to the gray matrix part, and the part that appears whiter than the matrix part (matrix) is the intermetallic compound. The absolute maximum length of each (the maximum value of the distance between any two points on the contour line of the particle) was measured. Then, the number of intermetallic compounds having a maximum length of 0.2 to 15.0 μm was counted, and the number density per unit area was calculated.
In the table, the intermetallic compounds having a maximum length of 0.2 to 15.0 μm are 1.5 × 10 ⁵ pieces / mm ² or more and are indicated by “○”, and 1.5 × 10 ⁵ pieces / mm ² Those less than are indicated by "x".

(2) Internal friction A test piece (width 10 mm x length 60 mm x thickness 0.7 mm, longitudinal direction is approximately parallel to the rolling direction) is cut out from the blank, and an internal friction measuring device (JE2-RT manufactured by Nihon Techno Plus Co., Ltd.) Measurement software: Internal friction was measured using JE-RT control software Version 2.6.1). Then, for each test piece, the average value of the internal friction values obtained by the three measurements was calculated and shown in the table as the internal friction value of each blank.
The half-value width method was adopted as the method for measuring the internal friction. The detailed conditions for the internal friction measuring device are: measurement method: free resonance type, measurement temperature: room temperature (about 24 ± 2 ° C), measurement atmosphere: in air, vibration method: non-contact electrostatic vibration method, test. Method: Two-point suspension method (hold the test piece with a suspension line at two points 13.44 mm from both ends in the longitudinal direction of the test piece), Detection method: Sound wave detection method, Scan step during test: 0.02 Hz, Scan range: It was an arbitrary setting (a range in which a stable value can be obtained between 950 and 1100 Hz based on the half-value width method is arbitrarily set, and the width of the scan range is 30 to 100 Hz).
If the internal friction is 1.5 x 10 ^-3 or more, the damping factor is "○" (pass), and if the internal friction is less than 1.5 x 10 ^-3 , the damping factor is "x" (fail). I evaluated it.

(3) Proof stress: A test piece of JIS13B was cut out from the reference blank so that the tensile direction was parallel to the rolling direction. The proof stress (0.2% proof stress) was determined by performing a tensile test using this test piece in accordance with JIS Z 2241: 2011 (offset method). The tensile speed was 3 mm / min (up to 0.5% strain amount) and 20 mm / min (0.5% strain amount or later).
The yield strength is shown for reference.

The table shows the chemical composition of the blank and the substrate, and the results of measurement or evaluation in the above (1) to (3). The underline in the table indicates that the requirements of the present invention are not satisfied.

[Examination of results]
(Examination based on the table)
As shown in Table 1, No. In order to satisfy the provisions of the present invention, Nos. 1 to 3 and 6 have high internal friction and pass the damping factor (high damping factor). In addition, No. Nos. 1 to 3 and 6 showed high proof stress values.
On the other hand, No. In No. 4, since the Mn content was low and the number density of the predetermined intermetallic compounds on the surface was small, the internal friction was low and the damping rate was unacceptable.
In addition, No. In No. 5, the temperature of the homogenization heat treatment was low and the number density of the predetermined intermetallic compounds on the surface was small, so that the internal friction was low and the damping rate was unacceptable.

(Examination based on graph)
In the graph shown in FIG. 1, the internal friction η (× 10 ^-3 ) is on the vertical axis, and the number density of intermetallic compounds (× 10 ⁵ / mm ² ) having a maximum length of 0.2 to 15.0 μm is on the horizontal axis. And No. It is a graph which plotted the results of 1-6.
From the results of FIG. 1, it can be seen that there is a very strong positive correlation between "the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface" and "internal friction". It could be confirmed.
Further, from the result of FIG. 1, when the number density of the intermetallic compound having the maximum length of 0.2 to 15.0 μm on the surface is 1.5 × 10 ⁵ / mm ² or more, the internal friction η is 1. It was confirmed that it was 5 × 10 ^-3 or more.

(Consideration on SEM images)
The SEM image obtained when measuring the number density of the intermetallic compound of a predetermined size was an image as shown below when visually confirmed.
No. The SEM images 1 to 3 and 6 showed a state in which a large number of intermetallic compounds of a predetermined size were uniformly dispersed and present. Among them, No. In the SEM image of No. 1, no coarse intermetallic compound could be confirmed. In addition, No. In the SEM image of No. 3, since the Mn content was slightly high, it was confirmed that a certain number or more of intermetallic compounds of a predetermined size were present, although a small amount of coarse intermetallic compounds were generated.
No. In the SEM image of No. 4, it was confirmed that the number density of the intermetallic compounds of a predetermined size was small because the Mn content was small. Naturally, No. In the SEM image of No. 4, no coarse intermetallic compound could be confirmed.
No. In the SEM image of 5, it was confirmed that since the temperature of the homogenization heat treatment was low, a plurality of coarse intermetallic compounds were generated, and as a result, the number density of the intermetallic compounds of a predetermined size was reduced. ..

[Example 2: Laminated material]
[Preparation of test materials]
First, the material for the core material was dissolved, and No. The composition was adjusted so as to have the chemical composition shown in No. 11, and the ingot was cast in a mold (book mold). The size of the mold was 50 mm in height × 145 mm in width × 200 mm in length, and the casting temperature was 720 ° C.
Next, both sides of the obtained ingot were faced by 13 mm, and homogenized heat treatment was performed under the conditions shown in Table 2.

Further, the material of the skin material was dissolved, Si: 0.01% by mass, Fe: 0.017% by mass, Cu: 0.04% by mass, Mg: 4.0% by mass, Cr: 0.07% by mass, The components were adjusted so that Zn: 0.15% by mass, the balance was Al and unavoidable impurities, and the ingot was cast into a mold (book mold). The size of the mold was 50 mm in height × 145 mm in width × 200 mm in length, and the casting temperature was 720 ° C.
Next, both sides of the obtained ingot were faced by 2 mm, and homogenized heat treatment was performed at 540 ° C. for 4 hours.
After that, the material after the homogenization heat treatment is hot-rolled (starting temperature 540 ° C., finishing thickness 3 mm) with the time from the end of the homogenization heat treatment (when taken out from the soaking furnace) to the end of hot rolling as 3 minutes. ) Was performed.

Then, the skin material (thickness 3 mm), the core material (thickness 24 mm), and the skin material (thickness 3 mm) were welded together to form a three-layer clad material.
Then, this clad material is put into a furnace at 540 ° C., heated to 540 ° C., and then subjected to a homogenization heat treatment for holding for 1 hour and 30 minutes, and then from the end of the homogenization heat treatment to the end of hot rolling. Hot rolling (finishing thickness 3 mm) was performed with a time of 3 minutes. Next, the obtained hot-rolled plate was cold-rolled. The cold rolling was passed a plurality of times so that the material temperature did not exceed 100 ° C., and finally the plate thickness was 0.5 mm.
The ratio of the thickness of the skin material, the core material, and the skin material was approximately 10%: 80%: 10%.

Then, this cold-rolled plate was punched into a ring shape of 3.5 inch size (outer diameter of about 95 mm, inner diameter of about 25 mm), stacked, and subjected to straightening annealing. The straightening annealing was carried out by holding in the range of 260 ° C. to 320 ° C. for 8 hours.

After that, it was peeled off and No. A blank (thickness 0.5 mm) for a 3.5-inch HDD according to No. 11 was manufactured.
Then, the manufactured No. Using the blank according to No. 11, the proof stress and internal friction were evaluated by the same method as in Example 1.
Regarding the number density of intermetal compounds on the surface of the core material, use a rotary polishing machine (TegraPol-35 manufactured by Struers) and polish until the skin material can be removed by mechanical polishing (polishing with polishing paper) (plate thickness). Was polished to 0.437 mm), and after buffing and finish polishing using a rotary polishing machine (Labopol-30 manufactured by Struers), the measurement was carried out in the same manner as in Example 1.

The table shows the component composition of the blank core material and the result of the yield strength. The underline in the table indicates that the requirements specified in the present invention are not satisfied.

(Examination of results: Results in Table 2)
As shown in Table 2, No. In order to satisfy the provisions of the present invention, the core material of No. 11 has a high internal friction as a laminated material, and the result is that the damping rate is acceptable (high damping rate).

Although the present invention has been described in detail by showing embodiments and examples, the gist of the present invention is not limited to the above-mentioned contents, and the scope of rights thereof is interpreted based on the description of the scope of claims. There must be. Needless to say, the content of the present invention can be modified or changed based on the above description.

The aluminum alloy blank for magnetic disks and the aluminum alloy substrate for magnetic disks according to the present invention have Mn: 1.00% by mass or more and 10% by mass or less, Fe: 0.30% by mass or less, and the balance is Al and The number density of intermetallic compounds, which consist of unavoidable impurities and have a maximum length of 0.2 to 15.0 μm on the surface, is 1.5 × 10 ⁵ / mm ² or more.

Further, the aluminum alloy blank for a magnetic disk and the aluminum alloy substrate for a magnetic disk according to the present invention include a core material and a skin material provided on at least one surface of the core material, and the core material is Mn: 1. Of 00 mass% or more and 10 mass% or less, Mg: 3.0 mass% or less, Cr: 0.5 mass% or less, Zn: 0.4 mass% or less, Cu: 0.4 mass% or less. Number density of intermetallic compounds having at least one content, Fe: 0.30% by mass or less, the balance consisting of Al and unavoidable impurities, and a maximum length of 0.2 to 15.0 μm on the surface of the core material. Is 1.5 x 10 ⁵ pieces / mm ² or more.

Claims (4)

Mn: 1.00% by mass or more and 10% by mass or less,
The rest consists of Al and unavoidable impurities,
An aluminum alloy blank for a magnetic disk, characterized in that the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface is 1.5 × 10 ⁵ pieces / mm ² or more. A core material and a skin material provided on at least one surface of the core material are provided.
The heartwood is
Mn: 1.00% by mass or more and 10% by mass or less, Mg: 3.0% by mass or less, Cr: 0.5% by mass or less, Zn: 0.4% by mass or less, Cu: 0.4% by mass Contains at least one of the following
The rest consists of Al and unavoidable impurities,
An aluminum alloy blank for a magnetic disk, characterized in that the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface of the core material is 1.5 × 10 ⁵ pieces / mm ² or more. Mn: 1.00% by mass or more and 10% by mass or less,
The rest consists of Al and unavoidable impurities,
An aluminum alloy substrate for a magnetic disk, characterized in that the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface is 1.5 × 10 ⁵ pieces / mm ² or more. A core material and a skin material provided on at least one surface of the core material are provided.
The heartwood is
Mn: 1.00% by mass or more and 10% by mass or less, Mg: 3.0% by mass or less, Cr: 0.5% by mass or less, Zn: 0.4% by mass or less, Cu: 0.4% by mass Contains at least one of the following
The rest consists of Al and unavoidable impurities,
An aluminum alloy substrate for a magnetic disk, characterized in that the number density of intermetallic compounds having a maximum length of 0.2 to 15.0 μm on the surface of the core material is 1.5 × 10 ⁵ pieces / mm ² or more.

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