JPS59193541A - Al alloy for substrate of magnetic disk - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a magnetic disk and to improve the magnetic recording density by specifying the percentages of Al, Mg, Zn and inevitable impurities contained in an Al alloy so as to increase the strength. CONSTITUTION:This Al alloy consists of, by weight, 3.5-5.0% Mg, 0.5-3.0% Zn and the balance Al with inevitable impurities including <=0.10% Si, <=0.10% Fe, <=0.30% Cu, <=0.01% Mn, <=0.01% Cr, <=0.01% Ni and <=0.01% Ti. Mg and Zn can remarkably increase the hardness and strength of the alloy, and Si, Fe, Cu, Mn, Cr, Ni and Ti as inevitable impurities each form an intermetallic compound. Since the Al alloy having said composition has high hardness, when it is used as the material of the substrate of a magnetic disk, the surface can be converted into a much superior mirror finished surface by buffing in a relatively short time. Intermetallic compounds present in the matrix are fine and uniform, and nonmetallic inclusions have been removed by filtering molten metal or by other means, so the thickness of a magnetic recording medium can be reduced.

Description

Detailed Description of the Invention This invention-1 has high hardness and high strength, has intermetallic compounds uniformly and finely present in the base material, and has almost no nonmetallic inclusions, especially in the percentage of these The present invention relates to an AQ gold alloy that enables high recording density of magnetic disks when used as a substrate for magnetic disks that require high recording density.

Conventionally, magnetic disks have been known in which a film of a magnetic recording medium is formed on the surface of, for example, an AQ alloy substrate, and the substrate is usually made of AA standard 5086 AQ gold alloy Mn: 0.20-0. 70%, Mg: 3,
5-4.5%, Cr: 0.05-0.25%,
Al4 and unavoidable impurities, the remainder) are used.

On the other hand, in recent years, the storage capacity of magnetic disks has increased.

Shorter access time, lower price per bit.

There are increasing demands for smaller size and lighter weight, and in order to satisfy these demands, it is essential to increase the density of magnetic recording on magnetic disks.

In order to achieve such high density magnetic recording, it is necessary that the magnetic recording medium be free from defects, have a smooth surface, and have a wide and uniform film thickness.

However, when making magnetic recording media thinner, if large intermetallic compounds or non-gold 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). Therefore, a substrate free of large metal t'=+ compounds and non-metallic inclusions is required, but the above 5086 AI! In alloys, it is possible to reduce non-metallic inclusions by filtration of molten metal, etc., but since intermetallic compounds exist in a relatively large size, there is a limit to the thinning of magnetic recording media. There is.

Unfortunately, the smoothness of the magnetic disk surface is primarily due to the smoothness of the substrate surface, so the substrate is given a mirror finish, but the 5086 AQ gold alloy mentioned above makes polishing these easy. It does not have enough hardness to satisfy the requirements.

Furthermore, the stronger the substrate, the smaller the magnetic disk.
Although weight reduction and wall thickness reduction will be achieved, the 5086 AC alloy does not have sufficient strength to achieve these goals.

Therefore, from the above-mentioned viewpoints, the present inventors have determined that the material has high hardness and strength, is free of non-metallic inclusions, and has a fine structure in which the intermetallic compounds distributed in the material have a fine structure. As a result of conducting research to develop an AQ gold alloy with 1vf17: 3.0 to 5.0%.

Zn: (1,, 5-350 section.

Contains, and if necessary, Zr: 0.02-05%.

containing Sl, Ere, and as unavoidable impurities.
The content of CuCr, N11 and T] is less than or equal to the coefficient Sl,',0'-0, respectively.

1i’e: O, 1.0% or less.

CLI: 0.30φ or less.

1vln: 001% or less.

Cr: 001 Manbutoshita.

Nx: 0.01 inch or less.

'T'i, ', 0.01 or less.

An AQ gold alloy with a composition (hereinafter referred to as "double hereditary", "Tsushita φ indicates heavy hereditary") with the remainder consisting of AQ and other unavoidable impurities, has all of the above properties, and therefore this alloy is They discovered that when used as a substrate for a magnetic disk, it is possible to increase the density of magnetic recording on the magnetic disk.

This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below.

(Object 1) The primary component (() has the effect of significantly improving the hardness and strength of the alloy, but if its content is less than 30%, the desired high hardness and high strength cannot be achieved, and T Way 50
If the content exceeds 3.0-5.0%, rolling becomes difficult and large intermetallic compounds of Al4-Mg threads are formed. Established.

(b) Zn The Zn component has the effect of improving the hardness of the alloy without forming large intermetallic compounds, but if its content is less than 0.05%, the desired hardness improvement effect cannot be achieved. Not obtained,
On the other hand, if the content exceeds 30%, the castability and rolling workability will deteriorate, so the content should be reduced to 0.5%.
It was set at ~3.0%.

(c) The Zr7,r component has the effect of refining the crystal grains and intermetallic compounds of the alloy, so it is included as necessary, but if its content is less than 0.024, the desired refining effect cannot be achieved. On the other hand, if the content exceeds 0.5%, a large AQ-
Since Zr-based intermetallic compounds are formed,
Its content was determined to be 0.02 to 0.05.

(e) Si, Fe, Cu as inevitable impurities
, Mn, Cr.

1 Odor, and T1 All of these components have the effect of forming intermetallic compounds, and if their content exceeds the allowable value below, large intermetallic compounds will be formed in either case. Therefore, the content is Si:O,1
0% or less, Fe: 0.10% or less, Cu: 0.30q6
Hereinafter, Mn: 0.01% or less, Cr: 001% or less, Nl: 0.01% or less, and '1': 10.01% or less.

At this point, the present invention will be specifically explained using examples of AQ gold alloys.

Example A commercially available AQ metal having a purity of 997% or more is melted,
After adding alloying elements to this to prepare AQ alloy molten metal having the composition shown in Table 1, chlorine gas is blown in to degas it, a settling treatment is performed, and non-metallic inclusions are removed. [Aspect] After filtering with a large filter, the width is 100100O by direct cooling continuous casting method.
An ingot with dimensions of 2.500 mm in length x 600 mm in thickness is then heat-treated by holding the ingot at a temperature within the range of 500 to 540°C for 12 hours and allowing it to cool. Thinly cut both the top and bottom of the ingot to a thickness of lc+mmK.
The ingot has a thickness of 580 mm and is heated to 500°C and hot-rolled to form a hot-rolled plate with a thickness of 5 Tun.The hot-rolled plate is subsequently cold-rolled to produce a plate. Thickness: 2van
A cold-rolled sheet with a diameter of 200mj from this cold-rolled sheet.
By punching out a disc of n with a press, the present invention AQ
Discs of gold alloy ~9 and conventional 5086AQ alloy were manufactured, respectively.

Next, the resulting AQ gold alloy discs of the present invention ~9 and 5086 AQ gold alloy were subjected to pressure annealing at a temperature of 350°C for 2 hours, and then rough polished and further puff polished. The surface was polished to a mirror finish. Note that the polishing method was o2ho. In addition to measuring the puff polishing time required for each disk, the surface roughness of the surface for mirror finish was measured, and the maximum dimension of the intermetallic compound on the surface for mirror finish was measured. Furthermore, mechanical properties were also measured for the invention A [alloys 1 to 9 and 5086A epsilon alloy].

The results of these 41 tests are shown in Table 2.

From the results shown in Table 2, the AQ gold alloys of the present invention ~9 are as follows:
Both have higher strength and hardness than the conventional 5086 AQ gold alloy, and it is clear that they can be finished to a mirror surface with better surface roughness with a longer puff polishing time. The size of nonmetallic inclusions present in the thin matrix is also extremely small.

Note that the A9 alloy of the present invention is, for example, the above-mentioned 5086A
It may also be used as a clad layer with a commercially available A9 alloy such as A alloy, and in this case, the film of the magnetic recording medium is of course formed on the surface of the A9 alloy of the present invention.

As mentioned above, since the A2 alloy of the present invention has high hardness, when it is used as a substrate for a magnetic disk,
Not only can the surface be finished to an extremely mirror finish with a relatively short puff polishing time, but the intermetallic compounds present in the base material are fine and uniform, and non-metallic inclusions can be easily removed by molten metal filtration. Since the magnetic recording medium is removed by this method, the film thickness of the magnetic recording medium can be made thinner, making it possible to increase the density of magnetic recording.Furthermore, since it has high strength, it is possible to make the magnetic disk smaller and lighter. It has industrially useful properties such as the ability to

Claims (2)

[Claims] (1) 1 question 30-50%. Zn: 0.5-3.0%. , and the remainder is AQ and unavoidable impurities (the above is the amount), and Si as the unavoidable impurity,
i'e, Cu, Mn, Cr, Ni, and T
The content of i is the same as the weight, and is less than or equal to the Sl:O, IO ratio. 1i'e: O, J, 0% or less. Cu: 0.30% or less. Mn: 0. 0 1 %1 or less. Cr: 0.01% or less. Ni: 0. O1%J or less. 'I'+: 0.01% or less. An AQ alloy for magnetic disk substrates characterized by: (2) J: 3.0 to 50%. Zn: 0.5-3.0%. and further contains Zr: 0.02 to 0.5%. , with the remainder consisting of 80% and unavoidable impurities (hereinafter referred to as "double %"), and b 1 as an unavoidable impurity.
．． I Fe + Cu + Mn + Cr r Nl
The content of g and Tyu, also by weight, Si: 0.10% or less. 1i's: O, ], O% or less. Cu: 0.30 salary or less. Mr+', 0.01 or less. Cr: 0.01%, below. 1 inch 1001% or less. Ti: 0.01% or less. An AQ alloy for magnetic disk substrates characterized by: