# US 2019/0172487 A1 · Aluminum alloy plate for magnetic disc substrate, method for producing the same, and magnetic disc

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0172487 A1
- Document ID: US20190172487A1
- Status: Published application
- Kind: A1
- Application number: 16/265,884
- Filed: 2019-02-01
- Published: 2019-06-06
- Earliest claimed: 2016-08-01
- Applicants: Uacj Corporation; Furukawa Electric Co., Ltd.
- Inventors: Kotaro KITAWAKI; Takuya MURATA; Akira HIBINO; Naoki KITAMURA; Hiroki OTA; Yasuo FUJII; Hideki TAKAHASHI; Takashi MORI
- Web page: https://patentgrep.com/patent/US20190172487A1

## CPC

- G11B 5/73913: {Composites or coated substrates}
- C22C 1/02: by melting {(C22C1/1036 takes precedence)}
- C22C 1/026: {Alloys based on aluminium}
- C22C 21/06: with magnesium as the next major constituent
- C22C 21/08: with silicon
- C22F 1/047: of alloys with magnesium as the next major constituent
- G11B 5/73919: {Aluminium or titanium elemental or alloy substrates}
- G11B 5/8404: {manufacturing base layers}
- G11B 5/82: Disk carriers
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00)

## Abstract

An aluminum alloy plate for a magnetic disc substrate according to the present disclosure includes, in mass %, Mg: 3.0 to 8.0%, Cu: 0.002 to 0.150%, Zn: 0.05 to 0.60%, Fe: 0.001 to 0.060%, Si: 0.001 to 0.060%, Be: 0.00001 to 0.00200%, Cr: 0.200% or less, Mn: 0.500% or less, and Cl: 0.00300% or less, with the balance being Al and inevitable impurities, and an abundance of a Cr oxide having a maximum diameter of 3 to 10 μm observed in a metal structure is 1 or less per single side of a disc.

## Claims

### Claim 1

An aluminum alloy plate for a magnetic disc substrate, wherein the aluminum alloy plate comprises, in mass %, Mg: 3.0 to 8.0%, Cu: 0.002 to 0.150%, Zn: 0.05 to 0.60%, Fe: 0.001 to 0.060%, Si: 0.001 to 0.060%, Be: 0.00001 to 0.00200%, Cr: 0.200% or less, Mn: 0.500% or less, and Cl: 0.00300% or less, with the balance being Al and inevitable impurities, and
an abundance of a Cr oxide having a maximum diameter of 3 to 10 μm observed in a metal structure is 1 or less per single side of a disc.

### Claim 2 (depends on 1)

The aluminum alloy plate for a magnetic disc substrate according to claim 1, wherein the aluminum alloy plate comprises one or two of Cr: 0.010 to 0.200 mass % and Mn: 0.010 to 0.500 mass %.

### Claim 3 (depends on 1)

The aluminum alloy plate for a magnetic disc substrate according to claim 1, wherein the aluminum alloy plate comprises Be: 0.00001 to 0.00025 mass %.

### Claim 4 (depends on 1)

A method of producing the aluminum alloy plate for a magnetic disc substrate according to claim 1, comprising:
adjusting a melt in such a way as to provide a composition of the aluminum alloy plate as a melt adjusting step;
casting the melt as a casting step;
hot rolling a cast ingot to provide a hot rolled plate as a hot rolling step; and
cold rolling the hot rolled plate to provide a cold rolled plate as a cold rolling step,
wherein the melt adjusting step is a step of loading aluminum metal comprising Cl: 0.00300 mass % or less to adjust the melt.

### Claim 5 (depends on 4)

The method of producing the aluminum alloy plate for a magnetic disc substrate according to claim 4, wherein the melt adjusting step is a step of further loading a Cr raw material containing a Cr oxide: 0.50 mass % or less in the melt to adjust the melt.

### Claim 6 (depends on 1)

A magnetic disc, comprising a plating layer and a magnetic layer on a surface of a circular aluminum alloy substrate prepared using the aluminum alloy plate for a magnetic disc substrate according to claim 1.