JPS6372848A - Aluminum-based alloy sheet for magnetic disk - Google Patents

Abstract

PURPOSE:To improve the plating suitability of the titled alloy sheet to be obtained, by controlling respective contents of Fe, Mg, Cu, and Zn and also by specifying the size, etc., of an intermetallic compound. CONSTITUTION:A molten alloy consisting of, by weight, 3-5.5% Mg, 0.02-0.1% Fe, 0.05-0.3% Cu, 0.1-0.7% Zn, and the balance essentially Al is filtered and then cast to about 4mm thickness, which is passed through cold-rolling, blanking, annealing, and machining stages so as to be formed into an alloy sheet. Moreover, the intermetallic compound of Al-Fe, etc., to be a nucleus of film formation in the pretreatment and plating treatment of the above sheet is regulated so that its size is 0.5-4mum and also that of >=0.5mum exists 5,000 pieces per square millimeter. In this way, the alloy sheet having excellent plating suitability even after subjected to long-term pretreatment can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum-based alloy plate for magnetic disks,
More specifically, the present invention relates to an aluminum-based alloy plate for magnetic disks that has excellent plating properties due to the presence of a large number of fine intermetallic compounds.

[Prior Art] In general, substrates for disks such as magnetic disks, optical disks, and optical-magnetic disks (hereinafter, explanation will be given using magnetic disk substrates as an example) are non-magnetic and have rigidity that can withstand high-speed rotation. Furthermore, aluminum alloys have been conventionally used because of their excellent corrosion resistance.

Also, the distance between the magnetic disk base and the magnetic head is 1μ.
The smoothness of the disk substrate is an important characteristic because it is extremely narrow, less than m ho I, and rotates at high speed.

Furthermore, with the improvement in magnetic recording density in recent years,
The distance between the magnetic disk substrate and the magnetic head is becoming smaller and smaller, and the recording unit area (pit size) is also becoming smaller, so the size of the magnetic disk substrate is required to be as small as possible. It is required that defects in the substrate for use be as small and as few as possible.

As a method for reducing the roughness of a magnetic disk substrate, a polishing method has been proposed after forming a nonmagnetic hard film on an aluminum alloy substrate by anodizing or plating.

Regarding the technology of the magnetic disk substrate described above, the present inventor added Zn to the conventionally used 5086 alloy.
, invented a magnetic disk substrate with a limited content of Cu and Fe, and completed the application as JP-A-60-194040.

In order to improve the plating properties, Fe is included to form a large amount of intermetallic compounds that serve as the core of the plating, and Cu and Zn are also included to make the growth of the plating uniform and reduce the plating thickness. It was an invention aimed at.

However, to form a plating film, pretreatment such as degreasing and zinc replacement treatment is essential, and therefore a large amount of Al-F
Elimination of e-based intermetallic compounds due to pretreatment, large Mg-
The pretreatment of the 5i-based compound tends to cause dissolution, making it difficult to form a sufficiently thin film in some cases.

In other words, depending on the degree of final grinding/cutting, it is necessary to carry out pretreatment (alkali etching) for a long time, but with the alloy plates according to the conventional technology, it was difficult to carry out long pretreatment for a long time due to the presence of large compounds, etc. .

However, regarding making intermetallic compounds finer,
As described in Japanese Patent Publication No. 60-000140, it is possible to apply a thin plate continuous casting method, and as described in Japanese Patent Publication No. 60-000140,
1940=No. 10, a part of which is described. However, by sufficiently increasing the effect of intermetallic compounds as plating nuclei,
In addition, in order to avoid large holes caused by shedding and elution during pretreatment, it is necessary to further improve the various techniques described above.

[Problems to be Solved by the Invention] The present invention aims to improve the magnetic disk substrate as described above, as a result of repeated research on vA color by the present inventor, and has resulted in the formation of a specific number of intermetallic compounds per unit area. In addition, by specifying its maximum dimension and securing the core of the plating, and further minimizing the holes caused by compounds that fall off during long-term pretreatment, we can improve the uniformity of the plating film. We have developed an aluminum-based alloy plate for magnetic disks that allows for thinner plating.

[Means for Solving the Problems] The aluminum base plywood for magnetic disks according to the present invention is characterized by: 3 to 5.5 wt% Mg, 0.02 to 0.0 wt% Fe. lv
t%, Cu 0.05~0.3wt%, Zn 0.1~
It is an aluminum alloy containing G, 7wt% and the balance substantially consisting of Al, in which an intermetallic compound of 0.5μ or more is present at least 5.00011H, and the size thereof is 4μ.
m or less.

The aluminum-based alloy plate for magnetic disks according to the present invention will be described in detail below.

First, the components and content ratios of the aluminum-based alloy plate for magnetic disks according to the present invention will be explained.

Mg is an element that provides the strength necessary for a disk substrate. If the content is less than 3 wt%, the strength necessary for the disk substrate cannot be obtained, and if the content exceeds 5.5 wt%, MgO This makes it easy for defects to occur when used as a disk substrate. Therefore, the Mg content is set to 3 to 5.5 wt%.

Zn and Cu are elements that uniformly form a solid solution in the aluminum alloy and increase the effect of reducing the roughness and making it uniform during plating pretreatment and plating treatment,
There is no such effect when the Zn content is less than 0.1 wt%, this effect is small when the Cu content is less than 0.05 wt%, and this effect is less when the Zn content is more than 0.7 wt%. Not only is the effect saturated and it is economically wasteful, but depending on the ripe treatment method, stress generation due to aging or formation of coarse precipitates may have the effect of increasing roughness during pretreatment. Also, if the Cu content exceeds 0.3vt%, Al
- A large number of Mg-based precipitates precipitate at grain boundaries, and the roughness becomes large and non-uniform due to pretreatment.

Therefore, the Zn content is set to 0.1 to 0.7 wt%, and the Cu content is set to 0.05 to 0.3 wt%.

Fe is an Al-Fe based intermetallic compound (with Si as an impurity)
, Mn, Al-Fe-5i system, Al-F
The e-FvLn system also exists. ) and become the nucleus for film formation during pretreatment and plating treatment, so uniformly dispersing it has an effect on the uniform whiteness of the film, and this intermetallic compound has a sufficient effect as a nucleus. In order to achieve this, the size must be at least 0.5 μm or more, and in order to prevent holes from falling out during thin plating, the size must be 4 μm or less. , In order to form a uniform film, s of 0.5 μm or more is required.
, o o o pieces/+m" or more is required. In order to satisfy these conditions, the thickness of the cast plate should be taken into consideration, and F
The e content needs to be 0.02 to 0.1 wt%.

If the Fe content is less than 0.2 wt%, sufficient intermetallic compounds cannot be obtained, and if the Fe content exceeds 0.1 wt%, even if the individual intermetallic compounds are small in size, their distribution will be poor. It tends to be uniform, and as a result, as in the case of large dimensions, it is easy to form large holes in the pre-plating treatment. Therefore, the Fe content is set to 0.02 to 0.1 t%.

Si is an impurity that is inevitably mixed in, but Mg1Si
The St content is preferably 0.08 vt% or less because it is easy to form and fall off during alkali etching in pre-plating treatment.

In addition to the ingredients explained above, Mn, Ti, B, Cr
Even if such impurities are contained within the range contained in the JIS5086 alloy, they do not have any effect on the aluminum-based alloy plate for magnetic disks according to the present invention.

When casting a molten aluminum-based alloy with such a content and content ratio after filtering, it is necessary to increase the number of intermetallic compounds by reducing the casting thickness and rapid cooling. Cast plate thickness is 12+
@a1 or less. There is no limit to the thinner plate thickness, but the magnetic disk plate used as a soft material has a temperature of 320 to 370°C.
It is necessary to completely recrystallize the steel, and for this reason, it is essential that the amount of cold rolling is 30% or more. Therefore, the thickness of the cast plate is preferably 4ss or more.

The obtained cast plate is made into a disk plate through the steps of cold rolling, punching, annealing, and cutting.

Next, degreasing, etching, Zn substitution or 5ni(
The preprocessing such as conversion is repeated, and then, for example, N
Form a non-magnetic plating film such as 1-P.

If the thickness of this plating film is less than 3 μm, the disk surface will be rough due to the influence of pretreatment, and pits will easily remain.
Furthermore, since the amount of finish polishing will inevitably be small and a uniform plating film with small roughness cannot be obtained, it is better to form a plating film with a thickness of 3 μm or more, and from the viewpoint of the strength of the plating film. is preferably 5μ■ or more.

The plated disc manufactured in this way is
After final polishing, a magnetic film is further formed by plating or sputtering and used as a magnetic disk.

[Example] Next, an example of an aluminum-based alloy plate for a magnetic disk according to the present invention will be described.

Example 1 After filtering aluminum base metal molten metal having the components and content ratios shown in Table 1, Comparative Examples A to D were heated to 400 m
After casting to a thickness of 4 m, homogenization heating and hot rolling are performed to form a 4 m thick
After the thickness was set to m, cold rolling was performed to a thickness of 1,5 ff1I11.

Example A of the aluminum-based alloy plate for magnetic disks according to the present invention was filtered, cast to a thickness of 4III11, annealed at 450° C. for 6 hours, and then cold rolled to a thickness of 1.5 mm.

These cold-rolled materials were punched into a disk shape with an outer diameter of 95fflI11, made into a soft material by pressure annealing, and then the surface was cut by 0.12 mm on each side to obtain a disk substrate.

At this stage, the intermetallic compound distribution was examined and the results are shown in Table 2.

After degreasing the obtained disk substrate with trichloroethane, alkali etching (5% Na0I, 25°C, 45 seconds immersion) → neutralization (30% INOs, 25°C, 10 seconds immersion) → pickling (IINOs) :HF:)ItO=3:1:2.
25°C, 30 seconds immersion) - Zinc replacement (1st time, 120g/
I NaOH120g/1ZnO12g/1Feclt
-611,0150g/l KNaCjl, 05-4H
20゜g/INaNO1, 25℃, immersion for 30 seconds) - Pickling (20% HNO3, 25℃, immersion for 10 seconds)
-Zinc substitution (second time, same conditions as first time)-+N1-
After processing under the conditions of P plating (Blue Schumer manufactured by Nippon Kanigen, immersion at 90°C, plating thickness 8 nun), and polishing the surface treatment properties, the roughness of the plating after plating, and the plating surface,
Its surface accuracy was investigated.

Table 3 shows the evaluation results.

Explanation of the words in Table 3.

- Surface treatment properties: The surface after the second zinc substitution was observed.

○ Precipitates are uniform and even △ Intermediate precipitate × Coarse and uneven precipitates ・Plating adhesion: 90° bending.

O Plating that does not peel off × Plating that peels off even partially -Surface precision: The plated surface was mirror polished with a polishing allowance of 1.5μ, and 50 fields of view were observed using a microscope at 400x magnification.

No pits with a diameter of 02 μm or more △ 1 to 3 pits × 4 or more pits From Table 3, specify the cast plate thickness, the contained components, and the content ratio, and determine the intermetallic compound. The identified example A of the aluminum-based alloy plate for magnetic disks according to the present invention has the following characteristics compared to other comparative examples:
It can be seen that the plating properties are excellent even after long-term pretreatment. Note that there is no difference in mechanical properties.

Example 2 A molten aluminum-based alloy having the components and content ratios shown in Table 5 was cast to the plate thickness shown in Table 5, and heated at 450°Cx.
After annealing for 6 hours at -500°C for 4 hours, it was cold rolled to a thickness of 2n+m.

After punching and annealing these plates, finish cutting was performed to a thickness of 1.9+n+++.

These bases were evaluated in the same manner as in Example 1.

The results are shown in Tables 6 and 7.

From Tables 6 and 7, it can be seen that the aluminum-based alloy plate for magnetic disks according to the present invention has sufficient plating properties even if alkali etching is performed for a long time as a pretreatment.

[Effects of the Invention] As explained above, since the aluminum-based alloy plate for magnetic disks according to the present invention has the above-mentioned structure, a large number of intermetallic compounds are finely distributed, and it has an excellent property of improving plating properties. It is effective.

Claims (1)

[Claims] Mg3-5.5wt%, Fe0.02-0.1wt%,
Cu0.05-0.3wt%, Zn0.1-0.7wt
It is an aluminum alloy containing 5,000% of intermetallic compounds with a diameter of 0.5 μm or more, and the remainder substantially consisting of Al.
1. An aluminum-based alloy plate for a magnetic disk, characterized in that the aluminum-based alloy plate has at least 4 μm in size and has a size of 4 μm or less.