Aluminum alloy plate for magnetic disc substrate, method for manufacturing same, and method for manufacturing magnetic disc

Patent metadata

Field	Value
Publication number	US-9613648-B2
Application number	US-201515117209-A
Country	US
Kind code	B2
Filing date	Sep 24, 2015
Priority date	Sep 27, 2014
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

An aluminum alloy plate for a magnetic disk substrate with a flat and smooth ground surface, a production method by which the aluminum alloy plate can be produced at low cost and a magnetic disk are shown. An aluminum alloy plate for a magnetic disk substrate which comprises an aluminum alloy containing Mg: 3.0 to 8.0 mass % (hereinafter %), Cu: 0.005 to 0.150%, Zn: 0.05 to 0.60%, Cr: 0.010 to 0.300%, Fe: 0.001 to 0.030%, Si: 0.001 to 0.030%, (Ti+V+Zr): 0.0010 to 0.0100%, B: 0.0001 to 0.0010% with a balance being Al and inevitable impurities, wherein the density of a Ti—V—B—Zr-based inclusion having a maximum diameter exceeding 5 μm is 0 piece/6000 mm 2 and the density of a Ti—V—B—Zr-based inclusion having a maximum diameter of 3 to 5 μm is 1 piece/6000 mm 2 or less; a production method thereof; and a method for producing a magnetic disk.

First claim

The invention claimed is:

1. An aluminum alloy plate for a magnetic disk substrate
wherein the aluminum alloy plate comprises an aluminum alloy containing Mg: 3.0 to 8.0 mass %, Cu: 0.005 to 0.150 mass %, Zn: 0.05 to 0.60 mass %, Cr: 0.010 to 0.300 mass %, Fe: 0.001 to 0.030 mass %, Si: 0.001 to 0.030 mass %, further containing (Ti+V+Zr):0.0010 to 0.0100 mass %, B: 0.0001 to 0.0010 mass % with a balance being Al and inevitable impurities and
wherein the density of a Ti—V—B—Zr-based inclusion having a maximum diameter exceeding 5 μm is 0 piece/6000 mm 2 and the density of a Ti—V—B—Zr-based inclusion having a maximum diameter of 3 to 5 μm is 1 piece/6000 mm 2 or less.

2. A method for producing aluminum alloy plate for a magnetic disk substrate, which produces the aluminum alloy plate for a magnetic disk substrate according to claim 1 , comprising
a molten alloy holding step of holding a molten aluminum alloy in a holding furnace at 700 to 850° C. for 30 minutes or longer,
a casting step of casting a slab from the molten alloy held in the molten alloy holding step, wherein the temperature of the molten alloy at the start of casting is 700 to 850° C.,
a hot rolling step of hot rolling the cast slab, and
a cold rolling step of cold rolling the hot-rolled plate.

3. A method for producing a magnetic disk, comprising
a step of punching a circular shape out of the aluminum alloy plate for a magnetic disk substrate according to claim 1 and thus preparing a disk blank,
a step of flattening the disk blank by pressure annealing,
a processing step of lathing, grinding, degreasing and etching the flattened disk blank,
a step of zincating the processed aluminum alloy plate,
a step of base-plating the zincated aluminum alloy plate, and
a step of sputtering a magnetic material to a surface of the base-plated aluminum alloy plate.

Assignees

• Uacj Corp

Inventors

• Kitawaki Kotaro
• Hayashi Minoru
• Hashimoto Yoshiji
• Hisamoto Toshikazu

Classifications

• C22F1/00

  Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working (apparatus for mechanical working of metal B21, B23, B24) · CPC title

• B22D11/049

  for direct chill casting, e.g. electromagnetic casting · CPC title

• C22F1/047

  of alloys with magnesium as the next major constituent · CPC title

• B22D15/00

  Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor · CPC title

• B21B2001/225

  by hot-rolling · CPC title