Magnetic disc aluminum alloy substrate and manufacturing method therefor

Abstract

The present invention is: a magnetic disc aluminum alloy substrate characterized in being obtained from an aluminum alloy containing Mg: 4.5-10.0 mass% (written as % below), Be: 0.00001-0.00200%, Cu:0.003-0.150%, Zn: 0.05-0.60%, Cr: 0.010-0.300%, Si: 0.060% or less, Fe: 0.060% or less, the balance being obtained from Al and unavoidable impurities, the content of Mg-based oxides being 50 ppm or less, and prior to applying plating pre-treatment, (IBe / Ibulk)*(CBe)<=0.1000% when the maximum optical emission intensity of Be in the surface depth direction using a glow discharge spectrometer is (IBe), the mean optical emission intensity of Be in the interior of the aluminum alloy base material is (Ibulk), and the Be content is (CBe); and a manufacturing method therefor.

Description

technical field [0001] The present invention relates to an aluminum alloy substrate for a magnetic disk having excellent smoothness and strength of a metal plating surface and a manufacturing method thereof. Background technique [0002] The aluminum alloy disk used in the storage device of the computer is made of an aluminum alloy substrate having good plating properties and excellent mechanical properties or processability, and the aluminum alloy substrate complies with Japanese Industrial Standards (Japanese Industrial Standards, JIS) 5086 ( 3.5 mass % to 4.5 mass % Mg, 0.50 mass % or less Fe, 0.40 mass % or less Si, 0.20 mass % to 0.70 mass % Mn, 0.05 mass % to 0.25 mass % Cr, 0.10% by mass or less of Cu, 0.15% by mass or less of Ti, 0.25% by mass or less of Zn, the remainder of Al and unavoidable impurities) are used as raw materials (base). Furthermore, for the purpose of improving the pit defect caused by the drop-off of intermetallic compounds in the pre-plating tre...

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Problems solved by technology

[0010] However, in the method disclosed in Patent Document 1, there is a problem that a large amount of Mn is added, so that a large amount of coarse Al-Fe-Mn-based intermetallic compounds exist on the surface of the aluminum alloy substrate, and they fall off during the pre-plating treatment. Large depressions are generated and the smoothness of the metal plating surface is reduced

In addition, pits due to poor adhesion of zincate coating film or metal plating are also referred to as existing pits), but fine pits with a maximum diameter of 0.5 μm or more and less than 1 μm cannot be prevented. The generation of pits (hereinafter referred to as "fine pits"), the current situation is that the high smoothness of the target Ni-P metal plating surface cannot be obtained

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