Aluminum alloy substrate for magnetic disk and manufacturing method thereof

Abstract

The present invention provides an aluminium alloy substrate used for a magnetic disc, and a method of manufacturing the same. The aluminium alloy substrate is resistant to impact, has great flatness, and has a plated surface with excellent smoothness. The aluminium alloy substrate is characterized by comprising the following aluminium alloys: below 0.03 by mass of Si, below 0.03 by mass of Fe, over 3.5 and below 4.5 by mass of Mg, below 0.2 by mass of Cr, and at least one selected from over 0.01 and below 0.20 by mass of Cu and over 0.01 and below 0.40 by mass of Zn, the balance being Al and unavoidable impurities, wherein the degree of flatness is less than 5 [mu]m, and the area rate of equiaxed grains on the surface of the substrate is less than 30%.

Description

technical field [0001] The present invention relates to an aluminum alloy substrate for a magnetic disk used as a substrate of a magnetic disk mounted in a hard disk drive such as a mobile personal computer, a notebook computer, and a portable audio player, and a method for manufacturing the same. Background technique [0002] A hard disk drive (hereinafter, appropriately referred to as "HDD") has the following configuration: a magnetic disk formed on an annular disk, such as a magnetic film; a spindle motor that rotates the disk; and a magnetic head that reads and writes information on the disk. ; a swing arm that fixes the magnetic head to the front end; a voice coil motor connected to the base end of the swing arm. [0003] In addition, as HDDs mounted on mobile devices such as mobile personal computers, notebook computers, and portable audio players, so-called 2.5-inch HDDs and HDDs smaller than 2.5 inches (hereinafter, appropriately referred to as “compact HDDs”) are us...

AI Technical Summary

Problems solved by technology

Therefore, in Patent Document 1, the rolling rate per pass is set very low, but for this purpose, the number of rolling passes needs to be increased, resulting in a problem of poor industrial production efficiency.

In addition, in Patent Document 2, although a special rolling method such as twin-roll casting is used, there is a problem that new equipment investment costs are required.

[0016] In addition, in the technologies disclosed in Patent Document 1 and Patent Document 2, since the Mg content is large, the segregation of Mg to the grain boundary causes pits to easily occur at the grain boundary, and it is difficult to prevent surface defects. Therefore, the smoothness of the plated surface room for improvement

[0017] In addition, the technology disclosed in Patent Document 3 does not take into account the impact from the outside, so the yield strength is only about 100 to 120 MPa, and it is easy to deform due to the impact when it is dropped, so it has a disadvantage in terms of impact resistance. room for improvement

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