JPS6033333A - Al-alloy for magnetic disc substrate - Google Patents

Abstract

PURPOSE:To provide the titled Al-alloy having high hardness and high strength and capable of performing high density recording when used in a magnetic disc substrate, wherein Mg and Zr are respectively contained in a prescribed amount and Si, Fe, Mn, Cr, Ni, V and B are respectively contained in a predetermined ratio as inevitable impurities. CONSTITUTION:The aforementioned Al-alloy contains, on a wt. basis, 3-5% Mg and 0.03-0.5% Zr and further contains 0.1% or less Si, 0.1% or less Fe, respectively 1% or less Mn, Cr, Ni and V, 0.008% or less Ti and 0.001% or less S as inevitable impurities. In this Al-alloy, the intermetallic compound dispersed in its matrix is remarkably fine and almost no non-metallic impurities are present. In addition, if 0.0005-0.02% of B is further contained in the coexistence of Zr in the aforementioned composition, the fine pulverization of the intermetallic compound can be further promoted. When this Al-alloy is used in a magnetic disc substrate, miniaturization and wt. reduction can be achieved because it has high strength and high hardness.

Description

Detailed Description of the Invention The present invention has high hardness and high strength, has extremely fine intermetallic compounds dispersed in the matrix, and has almost no nonmetallic inclusions. When used as a magnetic disk substrate that requires characteristics,
The present invention relates to an AQ alloy that enables high recording density of magnetic disks.

In recent years, the storage capacity of magnetic disks has increased.

Shorten access time and reduce the number of paths per bit.

There has been a strong demand for smaller size and lighter weight, and in order to satisfy these demands, the first thing that needs to be done is to increase the density of magnetic recording on magnetic disks. The substrate that holds the film of the magnetic recording medium also needs to be lightweight and have high hardness and strength.

Due to these demands, various AQ alloys have come to be used as magnetic disk substrates, especially Mg: 3 to 6%.
An AQ alloy has been proposed as an AQ alloy that is lightweight, has high hardness and high strength, and has a composition (by weight, hereinafter the same) with the remainder consisting of AQ and unavoidable impurities1.On the other hand, magnetic In order to achieve high recording density, it is necessary that the magnetic recording medium be free from defects, have a smooth surface, and have a thin and uniform film thickness.

However, when making a magnetic recording medium thinner, if large intermetallic compounds or nonmetallic inclusions are present in the base material of the substrate, this can cause defects such as bit dropout (a phenomenon in which some information is not recorded). A substrate free of large intermetallic compounds and nonmetallic inclusions is required. For example, in the above Aε-Mg alloy, nonmetallic inclusions can be significantly reduced by molten metal filtration. Since the intermetallic compound exists in a relatively large size, there is a limit to how thin a magnetic recording medium can be made.

Therefore, the present inventors focused on the above-mentioned conventional Ag-Mg alloy, and conducted research to refine the intermetallic compounds dispersed in the base material without impairing the high hardness and high strength of this alloy. As a result, Si, Fe, and Mn are contained as inevitable impurities in the above AQ-Mg alloy, and are all intermetallic compound forming elements.

The contents of Cr, Ni, V, Ti+ and B are each less than 0.1 ratio of Si.

Fe: 0.1% or less.

Mn: 0.01 or less.

Cr: 0.01% or less.

N-coni 0.01% or less.

V: 0.01% or less.

Ti: 0.008 or less.

B: 0.001% or less.

In this state, Zr: 0.03-0.5%.

When Be: 0.00 is added, the intermetallic compound becomes significantly finer, and in coexistence with Zr, Be: 0.00
Section 05-0.02.

It was discovered that the inclusion of the intermetallic compound further promotes the refinement of the intermetallic compound.

This invention was made based on the above findings.Mg: 3-5%, Zr: 0.03-0.5
%, and if necessary, Be: 0.0O05~
002 and as an unavoidable impurity.

The content of Fe, Mn, Cr, Ni, V, Ti, and B is 0.1% or less for Si, and Fe
: 0.1% or less, Mn: 0.01% or less, Cr: 0.0
1% or less, Ni: 0.01% or less, V: 0.01% or less, Ti: 0.008% or less.

and B: 0.001% or less, the remainder has a composition consisting of Aε and other unavoidable impurities, and the intermetallic compounds dispersed in the substrate are particularly fine, making it excellent when used as a magnetic disk substrate. Demonstrates excellent performance. This is a characteristic of AQ alloy.

Next, A9 of this invention. The reason why the component composition of the alloy is limited as described above will be explained.

(a) The lvig component has the effect of improving the hardness and strength of the alloy, but if its content is less than 3 parts, the desired effect cannot be obtained; on the other hand, if it is contained in excess of 5 parts. Therefore, the content was set at 3 to 5, since coarse AA-Mg-based intermetallic compounds are likely to be formed, rather than being difficult to roll.

(b) Zr The Zr component has the effect of significantly refining various A1 alloy-based intermetallic compounds dispersed in the substrate, but if its content is less than 0.03%, the desired refining effect cannot be obtained. On the other hand, if the content exceeds 0.5%, a coarse AA-Zr-based intermetallic compound will be formed, so the content is set at 0.03 to 05%.

(C) Be The Be component, when coexisting with Zr, has the effect of further refining intermetallic compounds and significantly reducing nonmetallic inclusions, so a particularly high-quality magnetic disk substrate is required. However, if the content is less than 0.0005%, the desired effect of improving the above action cannot be obtained, while if the content exceeds 0.02%, further improvement may be obtained. Not only is there no effect, but 002
Since the content of more than 5% can cause toxicity during work, the content is set at 0.0005% to 0.02%.

(d) Unavoidable impurities Si, Fe, Mn, Cr, as unavoidable impurities
Ni, V.

Ti and B components are both intermetallic compound forming elements, so Sl: 0.1% and Fe: 0.1%, respectively.
, Mn: Ooo 1%, Cr: 0.01%, Ni
:0.01%.

V: 0.01%, Ti: 0.008%, and B:
Containing more than 1% of O and OO not only causes the formation of coarse intermetallic compounds, but also especially V, Ti, and B, which can cause stringer defects to occur on the substrate surface after polishing. Since this may cause the above-mentioned content, the content should not exceed the above upper limit.

Next, the Aε alloy of the present invention will be specifically explained using examples.

Example Using an ordinary reverberatory furnace, degassing treatment with chlorine gas, calming treatment, and non-metallic inclusion removal treatment with a refractory filter were used, each having the component composition shown in Table 1. After preparing the molten metals of the present invention Aε alloys 1 to 8 and comparative Ap and alloys 1 to 7, a direct cooling continuous casting method was performed to obtain width: 1200w x length: 2500mm x thickness: 300+.
Cast into an ingot with dimensions of u+, then into this ingot,
After holding at a predetermined temperature within the range of 510 to 540°C for 12 hours, heat treatment was performed by allowing it to cool to room temperature, and then the top and bottom surfaces were faceted to a thickness of 15+u+, followed by a temperature of 500°C.
Hot rolled while heated to ℃ to give a plate thickness of 251nfn.
This hot-rolled plate is further cold-rolled to obtain a cold-rolled plate with a thickness of 2 mm and a diameter of 200 mm.
A 7 tLm disc was punched out using a press, and then this disc was subjected to pressure annealing at a temperature of 350°C for 2 hours, followed by rough polishing and puff polishing to give the surface a mirror finish. A board with a board thickness of 18M was manufactured.

In addition, all of Comparative M Alloys 1 to 7 have compositions in which the content of any one of the constituent components and unavoidable impurities (those marked with * in Table 1) is outside the scope of this invention. be.

Next, the maximum intermetallic compound size and surface roughness on the mirror-finished surfaces of the resulting substrates of Invention Eightε Alloys 1 to 8 and Comparative A9 Alloys 1 to 7 were measured, and the tensile strength and Vickers hardness were measured. We measured the The results of these measurements are shown in Table 2.

From the results shown in Table 2, in the A1 alloys 1 to 8 of the present invention, conventional V-Mg alloys had a weight of 23 to 29 kg.
f/ma tensile strength and a Vickers hardness of about 60 to 75, it has equivalent high strength and hardness and ensures a good mirror finish surface. Furthermore, the intermetallic compounds are also significantly finer, whereas any of the constituent components and impurities, as seen in Comparative M alloys 1 to 7, and especially Comparative A9 alloys 2 to 7, It is clear that coarse intermetallic compounds will be generated if the amount is outside the scope of the present invention. Furthermore, particularly in Comparative Alloy 5, the content of T1 as an impurity was higher than the range of the present invention, so stringers were observed.

As mentioned above, the AA gold alloy of the present invention has high strength and high hardness, so when it is used as a magnetic disk substrate, it can be made smaller and lighter, and it can be polished in a short puff polishing time. A good mirror-finish surface can be obtained, and intermetallic compounds are extremely fine, and there are almost no nonmetallic inclusions, so it is possible to make magnetic recording media thinner without worrying about defects such as bit dropouts. It has industrially useful properties such as:

Applicant: Mitsubishi Aluminum Corporation Agent Tomi 1) Kazuo and 1 other person

Claims (2)

[Claims] (1) Mg: 3-5%. Zr: 0.03-0.5%. and has a composition (the above weight %) in which the remainder consists of AQ and unavoidable impurities, and Si as an unavoidable impurity,
The contents of Fe, Mn, Cr, Ni, V, Ti, and B are also the same weight %, and Si: 0.1 or less. Fe: 0.1 inch or less. Mn: 0.01% or less. CR20, Section 01 and below. Ni: 0101% or less. V: 0.01% or less. 'ri: 0.008 chi or less. B2O, OO1ch or less. An Al-alloy for magnetic disk substrates, characterized in that: (2) Mg: 3-5%. Zr: 0.03-0.5%. Furthermore, Be: 0.0005 to 0.02%. , and the rest is AP, and unavoidable impurities.
' (more than % by weight) and S as an unavoidable impurity
i, Fe, Mn, Cr, Ni, V, T
The contents of i and B are Si:O,:L% or less in weight%. Fe: 0.1% or less. Mn: 0.01 or less. Cr: 0.01 or less. Ni: 0.01 inch or less. V: 0.01 inch or less. Ti: 0.008 or less. B: o, oo191H or less. An M alloy for magnetic disk substrates characterized by: