JPH0225215A - Finish working method for rolling material and blank material for magnetic disk obtained by using the method - Google Patents

Abstract

PURPOSE:To minimize the quantity of a defect exposed on the surface of a rolling material after working by setting optimumly the ratio of a second plate thickness of a target after the finish working and a first plate thickness before the working. CONSTITUTION:A magnetic disk use blank 1 obtained by bringing an ingot of an Al alloy to rolling working has such a tendency as the distribution density of a defect decreases gradually in the internal direction from the surface in the plate thickness direction and increases again as it approaches the center part. By setting plate thickness T0 of the magnetic disk use blank material 1 of a stock to a prescribed value, based on a value of plate thickness T1 after finish-working so that an area in which said defect becomes minimum goes to the surface of a substrate 1a of the plate thickness T1 after finish-working, the quantity of the defect which is exposed on the surface of the substrate 1a and may be the cause of deterioration of the yield can be minimized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a finishing technique for rolled materials, and is particularly effective in reducing surface defects on a substrate obtained by finishing a blank material for a magnetic disk. Regarding a certain technology.

[Conventional technology]

For example, as a manufacturing method for a magnetic disk, which is a type of magnetic surface storage medium, a magnetic film made of a desired material is deposited on the surface of a substrate made of a non-magnetic aluminum alloy or the like by spin coating or sputtering. It has been known.

In this case, defects such as irregularities on the surface of the substrate impede the flatness of the magnetic film, adversely affecting information recording and reproducing characteristics, and become a factor that prevents improvement in recording density.

For this reason, a substrate is manufactured by performing finishing processes such as cutting and polishing to remove defects formed on the surface of a blank material made of a rolled aluminum alloy material or the like during rolling.

By the way, the thickness of the substrate after finishing varies depending on the diameter of the magnetic disk depending on the standard, but in the past, the finish on the surface of the blank material was determined regardless of the difference in the thickness of the substrate after finishing, as shown below. The amount of processing was almost the same.

In other words, for the 5.25 inch size, the blank material plate thickness is 2.
．． The substrate thickness after finishing is 1.9051 for 14 mm! For I11 and 3.5 inch sizes, they are 1.51!1I11 and 1.27 mm, respectively, and in both cases, the finishing processing amount is 0.23 to 0.24 ms,
The idea is to use a blank material with a certain finishing allowance added to the required thickness of the substrate after finishing processing, and to remove approximately the same amount of the surface of the blank material as it was rolled. Ta.

The finishing techniques for blank materials for magnetic disks are described, for example, in the August 1984 issue of "Machine and Tools" and Japanese Patent Publication No. 62-53586.

[Problem to be solved by the invention]

However, with the above-mentioned conventional technology, the distribution density of defects that occur inside the blank material varies from the surface of the blank material due to various conditions such as cooling conditions during ingot manufacturing before rolling and dust, temperature, and impurities during rolling. Changes in the internal direction are not taken into account, and for example, if the finishing amount is the same for a 3.5-inch size as for a 5.25-inch size, it will cause problems when manufacturing an aluminum alloy ingot before rolling. The area near the center of the plate thickness, where defects due to impurities and dissolved gases are concentrated after final solidification, becomes the surface of the substrate after finishing, and the process of manufacturing a substrate from a blank material due to the increase in surface defects. There is a problem that the fractionation of

Therefore, an object of the present invention is to reduce defects exposed on the surface of the rolled material after finishing by optimally setting the ratio between the target second plate thickness after finishing and the first plate thickness before finishing. It is an object of the present invention to provide a finishing method that can minimize the amount of finishing.

Another object of the present invention is to provide a blank material for a magnetic disk in which the first plate thickness is set so that the fractionation of the substrate of the second plate thickness after finishing is the best.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in Hyodo is as follows.

That is, the finishing method of the present invention is a finishing method that removes the surface of a rolled material having a first thickness to achieve a target second thickness, and which removes the distribution of defects in the thickness direction of the rolled material. The ratio of the target second plate thickness to the first plate thickness is set so that the region with minimal density is exposed after processing.

Further, the magnetic disk blank material of the present invention is a magnetic disk blank material having a first plate thickness manufactured by rolling an aluminum alloy, and the first plate thickness is a finished magnetic disk blank material. The thickness is 111% or less of the second plate thickness of the substrate obtained by processing.

[Effect]

According to the finishing method described above, the region where the distribution density of defects is minimal in the thickness direction of the rolled material having the first thickness is exposed on the surface of the rolled material that has been finished into the second plate thickness. , the amount of defects present on the surface of the rolled material after finishing processing can be minimized.

Further, according to the magnetic disk blank material of the present invention, for example, the second plate thickness after finishing processing is 1.27 mm.
By using a magnetic disk blank material with a first plate thickness of 1.4 mm as a material for a 5-inch size substrate, an area where the distribution density of defects in the thickness direction of the magnetic disk blank material is extremely small is created. can be exposed on the surface of the substrate after finishing, allowing for optimal fractionation.

〔Example〕

FIG. 1 is a cross-sectional view in the thickness direction of a blank material 1 for a magnetic disk of 3 or 5 inch size, which is an embodiment of the present invention, and shows the distribution of defects 2 in the thickness direction of the blank material for a magnetic disk. This is shown together with Diagram 3 showing .

In the case of this embodiment, the plate thickness T of the blank material 1 for a 3.5-inch magnetic disk. (first plate thickness) is set to 1.4 mm, and by performing prescribed finishing processes such as polishing and cutting, the plate thickness T required by the standard, (second
The substrate la has a plate thickness of 1.27 mm.

As a result, for example, if a magnetic disk blank material with a thickness of 1.5 mm is used as in the past, 5 mm
．． 0.23+s (1 side 0.115mm
) 1.27 mm substrate after finishing
The amount of defects on the surface A of a can be reduced by 50-70%, and the fractionation of the substrate 1a is the best.

That is, as shown in diagram 3 of FIG. 1, in the magnetic disk blank 1 obtained by rolling an aluminum alloy ingot, the distribution density of defects gradually decreases from the surface to the inside in the thickness direction. It tends to reach its minimum at the center, and then increase again as it approaches the center. This is because when producing aluminum alloy ingots, impurities and dissolved gases aggregate as defects in the center, which solidifies last. Since a large number of defects are formed on the surface side due to mechanical damage during rolling and foreign matter adhering to the surface, it is thought that the amount of defects is minimized in a certain region between the center and the surface.

In the conventional case, the finishing allowance is
Since the idea of applying the - rule regardless of the plate thickness T+ of a was established, for example, the plate thickness T was 1,5111I11 as a blank material for a 3.5 inch size magnetic disk.
1.27 mm substray) 1a
In this case, the area indicated by the broken line B in the figure, which is closer to the center and has more defects than the position with the least number of defects, is the surface of the substrate, and a large number of defects are exposed on the surface. This will lead to a decrease in fractionation.

On the other hand, in this embodiment, for example, the value of the plate thickness T1 after finishing process is 1.27 so that the area where this defect is minimum is the surface of the substrate la having the plate thickness T1 after finishing process.
Based on mm, the material magnetic disk blank No. 1
#i! l1fT. By setting 1.4 + nm to 1.4 + nm, it is possible to minimize the number of defects that are exposed on the surface of the substrate (1a) and cause a reduction in fractionation.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the Examples (although it is possible to make various changes without departing from the gist of the invention). Not even.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, the finishing method for a rolled material of the present invention is a finishing method for removing the surface of a rolled material having a first thickness to obtain a target second thickness, the method comprising: In order to expose the area with minimal defect distribution density after processing,
Since the target ratio of the second plate thickness and the first plate thickness is set, the region where the distribution density of defects is minimal in the thickness direction of the rolled material of the first plate thickness is set to the second plate thickness. can be exposed on the surface of the rolled material that has been finished, and the amount of defects present on the surface of the rolled material after finishing can be minimized.

Further, the magnetic disk blank material of the present invention is a magnetic disk blank material having a first plate thickness manufactured by rolling an aluminum alloy, wherein the first plate thickness is For example, the second plate thickness after finishing is 111% or less of the second plate thickness of the substrate obtained by finishing the 3.5-inch substrate. In, the first
By using a magnetic disk blank material with a plate thickness of 1°4, the area where the distribution density of defects is minimal in the thickness direction of the magnetic disk blank material is exposed on the surface of the substrate after finishing processing. This allows for optimal fractionation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross section in the thickness direction of a blank material for a magnetic disk according to an embodiment of the present invention, together with a diagram showing the distribution of defects. DESCRIPTION OF SYMBOLS 1...Blank material for magnetic disk, 1a...Substrate, 2...Defect, 3...Diagram showing the distribution state of defects, To...Thickness of blank material for magnetic disk (No. 1 plate thickness), T1... plate thickness of the substrate (second plate thickness), A... surface of the substrate by the finishing method of this example, B... the surface of the substrate by the conventional finishing method surface of the substrate in case.

Claims (1)

[Claims] 1. A finishing method for removing the surface of a rolled material having a first thickness to obtain a target second thickness, the method comprising: a distribution density of defects in the thickness direction of the rolled material; A method for finishing a rolled material, characterized in that a ratio between the target second plate thickness and the first plate thickness is set so that a minimal region of the plate is exposed after processing. 2. The rolled material is made of an aluminum alloy, and the first
2. The method for finishing a rolled material according to claim 1, wherein the rolled material has a thickness of 111% or less of the second thickness. 3. A magnetic disk blank material having a first thickness manufactured by rolling an aluminum alloy, the substrate having the first thickness obtained by finishing the magnetic disk blank material. A blank material for a magnetic disk, characterized in that the blank material has a thickness of 111% or less of a second plate thickness. 4. The magnetic disk blank material is used to manufacture a 3.5-inch magnetic disk in which the second plate thickness of the substrate after finishing is nominally 1.27 mm, and the first
4. The blank material for a magnetic disk according to claim 3, wherein the thickness of the blank is nominally set to 1.4 mm.