JPH04345914A - Blank material for magnetic disk substrate made of titanium - Google Patents

Abstract

PURPOSE:To hold the out-of-roundness and concentricity of the inner periphery and outer periphery of a substrate within specification values at a good yield by regulating the flatness of a rolled sheet to a prescribed value or below. CONSTITUTION:The cold rolled sheet as the blank material for the magnetic disk substrates made of titanium having various kinds of flatness is prepd. and is blanked as the material for the 3.5-inch phi disk substrate. The flatness of the cold rolled sheet is confined to <=10mm/1000mm, by which 25mum out-of- roundness and concentricity are obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for manufacturing titanium magnetic disk substrates.

0002

[Prior Art and Problems to be Solved by the Invention] Magnetic disks used as recording media for computers are
With the trend toward higher recording densities, magnetic disk substrates are required to have extremely superior shape characteristics. That is, it is required that the circularity of the inner circumference and the outer circumference be 25 μm or less, and the concentricity between the inner circumference and the outer circumference be 25 μm or less.

By the way, conventionally used magnetic disk substrates made of Al alloy lack heat resistance against high-temperature sputtering when a magnetic film (magnetic medium) is formed thereon, and in addition, thin-walled substrates have recently become thinner. The rigidity is insufficient to meet the demands of To meet these demands, new materials such as ceramic, glass, and titanium are being used for magnetic disk substrates. Among them, titanium is suitable as a magnetic disk substrate material because it has excellent heat resistance, high rigidity and strength, and high cleanliness.

Titanium is a difficult-to-process material and has poor formability, so it is required to minimize the amount of processing required after punching, and the roundness and concentricity of the punched material must be within the above specifications. It is. However, it has been practically difficult to achieve a high yield within these specifications using the punched product.

The present invention was made in view of the above circumstances, and it is possible to improve the roundness of the inner and outer peripheries and the concentricity of the inner and outer peripheries of a titanium magnetic disk substrate as-is with high yield and within specifications. The purpose of the present invention is to provide a titanium magnetic disk substrate material that can be used in

[0006]

[Means and operations for solving the problems] In order to solve the above problems, the present invention has a flatness of 10 mm/1000
To provide a titanium magnetic disk substrate material characterized by being made of a rolled plate with a diameter of less than mm.

Magnetic disk substrates are manufactured by punching a substrate material into a ring shape, and the roundness and concentricity after punching are greatly influenced by the flatness of the punching material. In other words, if the flatness of the material is poor, the roundness and concentricity will also be poor. As described above, titanium magnetic disk substrates are difficult to process, so they are hardly processed after punching, and the roundness and concentricity of the titanium disk substrate must be within specs in the punched state. Therefore, it is necessary to strictly define the flatness of the titanium magnetic disk substrate material.

As a result of various studies conducted by the inventors of the present application, it has been found that when the flatness of the substrate material is worse than 10 mm/1000 mm, the circularity of the inner and outer circumferences is less than 25 μm, and the concentricity between the inner and outer circumferences is less than 25 μm. It has been found that it is difficult to achieve specifications of 25 μm or less with good yield. Therefore, in this invention, the flatness of the titanium magnetic disk substrate material is specified to be 10 mm/1000 mm or less.

[0009] The flatness here is the length of the material 10
The displacement in the vertical thickness direction per 00 mm is shown. Further, roundness indicates the maximum value of displacement from a perfect circle, and concentricity indicates the deviation between the center of the inner circumferential circle and the center of the outer circumferential circle of the disk substrate. Further, in order to make the substrate material have a predetermined flatness, a well-known method such as a cold leveler, a skin pass, etc. can be employed.

0010

[Embodiments] Examples of the present invention will be described below.

[0011] Cold-rolled plates as titanium magnetic disk substrate materials having various flatness degrees shown in Table 1 were prepared, and
For inch φ disk substrates (inner diameter 25mm, outer diameter 95mm)
), 100 sheets were punched out for each condition. The roundness of the inner and outer peripheries and the concentricity of these were measured with the blanks as they were punched. Table 1 shows the average values of roundness and concentricity at that time, as well as the yield in which both roundness and concentricity were 25 μm or less.

As is clear from Table 1, it was confirmed that if the flatness of the cold-rolled plate as a substrate material was 10 mm/1000 mm or less, excellent roundness and concentricity of 25 μm or less could be achieved with a high yield. .

On the other hand, the flatness is 10mm/100
If it exceeds 0 mm, the roundness and concentricity will be extremely reduced,
It was confirmed that the yield within the specification of 25 μm or less was extremely low.

In this embodiment, a cold-rolled plate was used as the disc substrate material, but the present invention is not limited to this, and the same effect can be obtained with a hot-rolled plate. In addition, the board size is not limited to 3.5 inch diameter, for example, 2.
．． Of course, similar effects can be obtained with other sizes such as 5 inches φ.

[0015]

[Table 1]

[0016]

According to the present invention, the circularity of the inner and outer peripheries and the concentricity of the inner and outer peripheries of titanium magnetic disk substrates can be kept within specs with good yield even when punched. A magnetic disk substrate material is provided.

Claims (1)

[Claims] 1. A titanium magnetic disk substrate material comprising a rolled plate having a flatness of 10 mm/1000 mm or less.