JPS5816059A - Manufacture of al alloy plate for magnetic disc substrate - Google Patents

Abstract

PURPOSE:To manufacture the titled alloy plate with superior surface accuracy by annealing and cold rolling a plate cast continuously from a molten Al alloy contg. Mg essentially, Ti and B selectively and Fe, Mn, Si and Cr each restricted to a specified amount or below. CONSTITUTION:A molten Al alloy contg., by weight, 2.0-3.5% Mg as an essential alloying element, 0.004-0.08% Ti and 0.0005-0.01% B as selective alloying elements and Fe, Mn, Si and Cr each restricted to <=0.1% is used. The molten alloy is passed through a filter applying electrochemical absorption phenomenon to remove nonmetallic oxides in the molten alloy, and it is cast into a continuously cast plate having 4-10mm. thickness. The cast plate is quenched, optionally cold rolled at >=25% draft, annealed at 400-550 deg.C for 1-48hr, and further cold rolled at >=30% draft.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for manufacturing an AI-based metal plate which is a material for a magnetic disk substrate with a surface precision of OII.

Magnetic disks, which have traditionally been used as electronic calculation IIOI storage media, are made by cutting the surface of an Aj-based metal plate to a predetermined thickness, and then applying precision cutting or precision polishing to form a magnetic thin film on the AlO-based surface. It is coated with
The following characteristics are generally required for magnetic disk substrates.

111 Good surface area after precision polishing or precision cutting, i.e. no distortion or minute undulations of the base metal body ν-bX'
&- thing.

(In order to form a magnetic thin film with a constant thickness, there should be no surface defects such as protrusions or holes that would adversely affect the process. Even if the defects are minute, they may be concentrated locally.
There isn't.

131 must have enough mechanical strength to withstand high-speed rotation when used.

14) Non-magnetic and lightweight.

(6) Possess a certain degree of corrosion resistance and heat resistance.

On the other hand, 6086 alloy is currently widely used for magnetic disk substrates, but in recent years the demand for larger capacities and higher recording densities for magnetic disks has become stronger, and the magnetization area per bit has become smaller. In addition, magnetic films have become thinner and the flying height of magnetic heads has also been reduced. However, the 5086 alloy does not provide a base suitable for high density in terms of surface precision and surface defects among the above-mentioned properties.

Inventor I! Under the above-mentioned circumstances, ifi has been conducting research to improve the surface precision of Aj base metal O for magnetic disk substrates, and has developed an Al base for magnetic disk substrates of the above-mentioned coating type. For alloy plates, we established a manufacturing method that satisfies the 141 targets and filed a patent application (patent application filed in 1973).
-116? and patent application No. 611-71196). However, in recent years the demands for increasing the density of magnetic disks have become even more severe, and in order to meet these demands,
(a treatment method in which after precision cutting or precision polishing is performed, anodization is performed to a thickness of about 6 μm, and then final polishing is performed to make the anodized layer about 1 μm thick, and then a magnetic thin film is sputtered on top of the anodized layer) However, by using positive WWI, the surface hardening of the distal substrate can be significantly increased compared to the case of only Aj-based alloy, and the surface precision can be greatly improved by polishing.

That is, the method involves precision cutting or precision polishing the A// alloy and then applying a magnetic thin film onto the A/ base alloy.

The surface hardness of 1111 alloy plate is HY company 50
~70s degree (soft material > IcL) Even if you increase the surface area by 1, there is a limit naturally.For this, we precision cut or precision polish the Al-based alloy plate to make the rear corner 41 m?&%
/, when finishing precision polishing is performed again, the surface hardness becomes HV.
s, 100 or more, the surface hardness is significantly increased compared to the case of only A11 & alloy.
The method of applying anodization to an A/based all-alloy plate is considered to be an extremely effective method in meeting the demands for higher recording densities of magnetic disks.

Based on the above-mentioned O-like knowledge, the present inventors have carried out research with the aim of developing an A/base alloy plate that can obtain excellent surface precision by adopting the anodic oxidation method. In order to apply.

We have come to the conclusion that we need to solve the serious new problems listed above.

(1) It is necessary to add Mg to improve strength.
When N, AI-high Mg alloy is rapidly solidified, grain boundary busy β phase (
A/gMgB) segregation may occur. This β phase formed during casting poses no problem when a magnetic film is simply applied after precision cutting or precision polishing. However, when anodic oxidation is performed, the β phase is eluted and becomes a large defect, so even if such an anodic oxide film is finished and precisely polished, good surface precision cannot be obtained.

During the 1!1 atomization, the area around the AI-(Fs, Mu, Cr) x crystallized substances dissolves, so if these crystallized substances are large, the surface precision after final polishing will deteriorate.

(11) Mg2Si-based crystallized substances themselves and their MFM-1IXfII occur during anodization, etc., and significantly reduce the surface precision after final polishing.

The present invention was completed as a result of intensive research to solve the above-mentioned problems associated with the adoption of the anodization method and to establish a method for manufacturing At-based alloy plates for magnetic disk substrates with excellent surface area. And what is its composition?

Mg as an alloying element: 10 to 8.5 g II (lfi
ll, jJl (same as below) is included, and T: 0.0
A/M alloy containing selectively 04~00g and l: 0.0005~0.0111 and suppressing fiTh, Fs, Mn, S and cr to 4G, 11G or less is included. Continuous casting is performed so that the plate thickness is 4 to 1・■, *
*The plate is annealed at 600~ago℃ for 1~48 hours.

4140 G-5it O'C"t"1~4 J1 cold rolled at a working rate of 80 or more, or a cast plate obtained in the same manner as above and cold rolled at a working rate of 2611 or more.
Time annealing, I! There is a required V for cold rolling at a working rate of KI011 or higher and for ζ.

First, alloy elements defined in the present invention will be explained.

Mg is an indispensable O component that provides a specified transverse wave strength to the disk substrate.It must be contained at least in g,on or more. The formed product is cut by cutting the distal base.
When h-polishing is carried out, the β phase is excessively dissolved into Kn, resulting in depressions (1k), and the surface precision after final polishing is significantly reduced.

If the Mg content is 8.6 or less, almost no β phase will be formed during casting, and even if it is formed, the Mg phase will be removed during the annealing process described later.
lj6g diffuses and the β phase disappears. That is, M in the At-based alloy
If the g amount is 8.6 or less, the β phase does not exist during anodization.

Good surface precision can be obtained by subsequent final polishing.

7i and B are effective elements that refine the structure of castings and prevent micro-segregation, and in order to effectively exhibit these effects, Ti: 0.00411 or more and B: 0.000.
It is desirable to add 511 or more alone or in combination. However, T&0〇, OSm.

If B exceeds 0.01-, most of the excess will be removed in the first step of the filtration process using a filter that uses electrochemical adsorption, so it is wasteful to add any more. .

F@, Mn, and Cr all have mul-(re) at the time of casting.

When a Mn, Cr) x system crystallized substance is formed and electrolytic oxidation is performed after cutting the disk substrate, the surrounding area of the crystallized substance is dissolved and the surface precision is degraded. Therefore, At-(F.

The number and size of Mn, Cr)

S5 forms a crystallized product of Mgg8i (Mg281 dissolves itself during anodic oxidation, and at the same time dissolves its surroundings, reducing the surface roughness. Therefore, it is necessary to suppress it to 0.1 or less.

f4. Since the AtFiG4 used in the present invention has a purity of 9.811 or higher, the amount of Cu, Kn, etc. that are inevitably contained in At is at the level of impurities. Also, no defects were observed during anodization.
There is no actual harm.

In the present invention, after melting the above-mentioned At-based alloy, it is passed through a filter using an electrochemical adsorption phenomenon to remove nonmetallic inclusions in the molten metal, and then continuous casting is performed. However, in order to achieve the objective Ii, the plate thickness must be increased from 4 to 4) in the continuous casting process. In conventional continuous casting, the thickness -tIxso.

It is customary to obtain a 0 slab of ~600 cod seismic intensity.

However, the results confirmed by the inventors through experiments show that if the thickness is within the slip thickness, rapid cooling will be difficult, and crystallized substances will grow during the slow cooling and solidification stage. As can be seen, it is possible to reduce the size of crystallized particles to 2.6μ or less, and when Zero sets the thickness of the plate to 10μ or less in the continuous casting process, the plate is cooled extremely rapidly. As a result, the crystallized substances can be made extremely fine, and at the same time, the crystal grains can be made fine in combination with the added effect of the finer element OII. By the way, the slab thickness "S" obtained by conventional continuous casting is WOO ~ 6
00■ The thickness of the O crystallized material is about 12■, but when the thickness is set to 10- or less, the cooling speed is 1.
You can become more busy than 0 times.

Correspondingly, the crystallized material has an IZ of 1, which is less than L6μ theory.

However, since the crystal grains become finer together with the effect of adding the four refining elements, almost no crystallized O microsegregation occurs.

Therefore, the At-based alloy sheet that was cold-open rolled after that was ! For the first time, fine crystallized substances can be obtained in the form of finely dispersed particles,
Even if this is machined and polished.

There is no risk of causing unevenness caused by coarse crystallized substances or ripples caused by micro-segregation.

Award if a rapid coagulation method as mentioned above is adopted.

A β phase is formed in the solidified structure, but this can be solved by changing the amount of Mg added as described above. It can be solved by making Todoroki Ls 臘下, and even if it were to be formed a little, it would be 8.
If the amount is 5 or less, it can be eliminated by the annealing step described below. The local unevenness of the macrostructure caused by unevenness of surface and rice grains I-ν and # products, which tends to occur during continuous casting, can be eliminated by the combination of annealing conditions and cold rolling conditions described below. I can do it all.

Usually, ingots with a thickness of 5 to 80 mm are applied with a solidifying agent of about 5 to 80 mm, so even if problems caused by the above two points occur, they will be scraped off when facing the surface.

There is no longer any problem in the subsequent pressing process.

However, in the case of the button of the present invention (with a casting thickness of 4 to 30 mtC), the surface layer thickness that can be removed with one solid agent is extremely small, and it cannot be expected that the solid agent will solve the problem. It is necessary to take countermeasures.Furthermore, during the processing process as a disk base, if the material is coarsely grained or non-uniform during final polishing or final cutting after it is made into a soft material, There is a tendency for the surface precision of finish polishing or finish cutting M* to decrease.In order to prevent these problems, it is necessary to reduce the crystal grain size to 0.045so+ or less when used as a soft material. be.

In response to these demands, the objectives can be achieved by the following two methods.

[1] The above-mentioned 4-10cm thick cast plate was heated to 300-1!56℃
The method includes annealing for 1 to 48 hours, followed by cold rolling to a predetermined thickness for more than 80 working steps.

[2] After cold rolling a cast plate having a thickness of 4 to 1 (Ism) at a processing rate of 2b- or more, intermediate annealing at 40G-650°C for 1 to 48 hours, and further O-processing the sheet to a predetermined thickness of 80 bags or more. A method of cold rolling with a steel rod.

In the above [1] O method, if the annealing degree is less than 600°C, fine precipitates will precipitate, and local unevenness in the macrostructure during casting cannot be made harmless, whereas if it exceeds 560°C, local melting will occur. occurs. The annealing time must be set in the range of 1 to 48 hours. In other words, the above-mentioned local unevenness cannot be rendered harmless if it is left for less than 1 hour, while no further effect can be obtained even if it is left for 48 hours.The higher the processing rate after annealing, the finer the recrystallized grains become. In order to achieve target 11 grain size, the processing rate must be 80 mm or higher.

According to the method [2] above, it is possible to lower the annealing temperature by performing cold compression before and after annealing.

That is, if cold rolling is performed before intermediate annealing, crystal grains become finer in the intermediate annealing step, and problems caused by local unevenness of the macrostructure are suppressed. However, in order to ensure such an effect, the processing rate must be set to 261° C. or higher, and if the processing rate is less than this, the objective cannot be achieved. Intermediate annealing can be performed at a lower temperature than in method [1], but if it is below 400°C, a large amount of fine precipitate agIII will precipitate, and the recrystallized grains during intermediate annealing will be coarse and unrestricted], resulting in a macrostructure. Besides, the recrystallized grains after "cold rolling + softening annealing" become significantly coarser. On the other hand, the intermediate annealing temperature is 6
When the temperature exceeds 60°C, local j1M# occurs as in the case [1]. If the intermediate annealing time is not longer than 1 hour, the above effect will not be effectively exhibited.On the other hand, if it exceeds 48 hours, the recrystallized grains will become coarse and the target will not be achieved (1k). t) K is effective because large recrystallized grains become fine and eliminate local unevenness in the macrostructure. In order to reduce the crystal grain size to 0.045 μm or less in order to ensure sufficient surface precision for use as a disk substrate, the processing rate must be greater than son. Therefore, [2]
When implementing the above method, the thickness of the cast plate and the thickness of the final product must be taken into consideration, and the cold working rate applied after intermediate annealing 0* must be adjusted to satisfy the above requirements.

In this way, by appropriately controlling the annealing and cold-opening rolling conditions after casting, it is possible to prevent
The local unevenness of the macrostructure caused by the twin pattern and 1lflltr6 is rendered harmless, and furthermore, the β phase that may be produced in trace amounts is completely eliminated.

The present invention summarizes the above OII/I! The formation of the republican β phase is prevented by refining the macrostructure and drastically reducing electrochromic segregation by changing the type and amount of the wetting alloy source and by reducing the final plate thickness through continuous casting. However, by setting post-casting annealing and cold rolling conditions, we succeeded in rendering the local unevenness of the macrostructure O harmless. Therefore, after cutting or polishing the ζOIt-based alloy plate, the magnetic disk substrate with extremely high surface precision can be created by finishing polishing.
In response to the request for higher recording densities on magnetic disks, the company was able to achieve 84 results.

Next, examples of the present invention will be shown.

Compositions AC (inventive material) and B (comparative material) OA shown in Example Table 1
The 7-base alloy melt was treated with a filter using an electrochemical adsorption phenomenon according to a conventional method to remove nonmetallic inclusions, and then continuously molded into a plate with a thickness of 6 Jsg*. , Incidentally, the surface crystal grains of the # heavy plate were reduced to 0.06JS by adding 1wk pongeeing agent.
I arranged it so that it would be sm. 4. These #heavy boards.
! ■After cold open rolling with thick O and annealing at 450℃ for 4 hours, j! The material was cold-open rolled on a 2.2 m diameter plate.

This cold-rolled material is punched into a disc shape! After annealing at 50'C with 2 o'clock opening strain relief] one side was 0. Roughly cut each IN, annealed for 2 hours to remove strain in WIICIlISO"C, and then precision cut. Then, the #I finely machined surface was anodized to a thickness of 6 μm under the conditions shown in Table 2. Oxidation was carried out.The surface hardness at this time is shown in Table 3.As is clear from Table 8, the surface hardness of the Kllll alloy is approximately twice that of the Al-based alloy No. 11. result,
The surface precision of the anodic oxide film after final polishing can be significantly improved compared to precision cutting or polishing of Al-based alloys.

Table 1 Surface Hardness nv Table 4 shows the magnetic head flying characteristics of the disks obtained by final polishing each of the anodic oxide films obtained above to a thickness of 8 μm. However, test conditions #i were a rotation speed of 8100 rpm and a magnetic head flying height of 0.2 μm.

In this test #i, the waviness of the disk base metal body.

This is a characteristic test that includes all factors such as straightness, minute ridges on the base] and surface accuracy. For reference★In the conventional 6086
Characteristic test results of the disk base s1 obtained from the alloy are also listed.

As is clear from the 4th award, Fi
Coarse crystallized material (167*m or more) has a protrusion of 0.2 μm and 11 degrees or more, so the magnetic head can fly stably at a height of 0.2 μm without any damage. On the other hand, in composition B (comparative example) and composition A (product of the present invention) -〇, the crystallized substances were tt,! Spm or less, the protrusions caused by this are small and the head can fly stably. However, as shown in Table 6, in the BM composition (comparative example), there were many recording errors due to large defects due to the elution of the β phase, which seriously affected the reliability of the magnetic disk. That is, in order to ensure excellent performance when used as a material for magnetic disk substrates, including those that undergo positive tIs layering, it is essential to meet the requirements stipulated herein.

■ Applicant: Kobe Steel Works Co., Ltd.

Claims (1)

[Claims] (1) Essentially contains Mg: 10 to 8.6 tatami (heavy) as alloying elements, Ti: 0.004 to 0.0
8 J-B: L6410! In addition to selectively containing S-0,0111, F@, Mn, 8i and Qr are each annealed at lI°C for 1 to 48 hours, and then cold rolled at a processing rate of SO excellent or higher. . A method for producing an At-based alloy plate for a magnetic disk substrate, which is used by anodizing. (Mg as 11 alloying element: 10~J1.lS1g
(Heavy weight. The same applies hereinafter), Ti: 0.064 to 0.
08- and B: Atto, Fe, Mu, Si and (r
Using Aj base water bath which suppresses each to 0.111 or less.
Continuous casting was carried out in row 1 so that the plate thickness was 4 to 10 m, and the cast plate was cold rolled at a processing rate of 21 or more.
Annealed at ~ago℃ for ~48 hours, llK80mIt
A method for producing an At alloy plate for one-layer magnetic disk, which is characterized by cold rolling at a processing rate of O゛ and is anodized.