JP3833933B2

JP3833933B2 - Manufacturing method of blank material made of aluminum alloy for memory disk and blank material manufactured by the manufacturing method

Info

Publication number: JP3833933B2
Application number: JP2001379247A
Authority: JP
Inventors: 泰之大関
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2001-12-12
Filing date: 2001-12-12
Publication date: 2006-10-18
Anticipated expiration: 2021-12-12
Also published as: JP2003183793A

Description

【０００１】
【発明の属する技術分野】
本発明は、コンピュータの記憶媒体であるメモリーディスク用アルミニウム合金製ブランク材の製造方法および前記製造方法により製造されたメモリーディスク用アルミニウム合金製ブランク材に関する。
【０００２】
【従来の技術】
アルミニウム合金製ブランク材は、アルミニウム合金の冷間圧延板からプレス打抜きされたドーナツ状板を面取り加工後、複数枚を積層し、これを加圧焼鈍して製造される。この加圧焼鈍後のブランク材は、その後、研削加工→Ｎｉ−Ｐメッキ処理→表面研磨→メディア加工（記憶媒体を表面に形成する）の各工程を経てハードディスクに加工され、ハードディスクドライブに組み込まれる。前記メディア加工はテクスチャー、スパッタリングなどの方法により行われる。ところで、３．５インチのハードディスクの記憶容量は、この１年で１０ＧＢから４０ＧＢに増加し、今後もさらに高容量化することが予想されている。高容量化には、メディア加工の際に、ブランク材表面に記憶媒体を整然と形成する必要があり、そのためにはブランク材には、研削加工後において、表面のうねりが小さいことが要求されている。
【０００３】
【発明が解決しようとする課題】
しかし、従来の製造方法は、（１）打抜加工後のドーナツ状板の端部にダレが生じて面取加工に時間が掛かる、（２）研削加工後のブランク材に表面うねりが生じるといった問題があった。
このようなことから、本発明者等は、前記問題の解決策を検討し、前記（１）の問題は冷間圧延における最終中間焼鈍条件および前記最終中間焼鈍後の圧延率を規定することにより、また（２）の問題は前記最終中間焼鈍条件および圧延率に加えて、加圧焼鈍条件を規定することにより解決し得ることを知見し、この知見を基にさらに検討を重ねて本発明を完成させるに至った。本発明の目的は、打抜加工後のドーナツ状板にダレが生じ難く、研削加工後において表面うねりの小さいメモリーディスク用アルミニウム合金製ブランク材の製造方法および前記製造方法により製造されたメモリーディスク用アルミニウム合金製ブランク材を提供することにある。
【０００４】
【課題を解決するための手段】
請求項１記載発明は、Ａｌ−Ｍｇ系合金鋳塊に、ソーキング、熱間圧延、冷間圧延（中間焼鈍含む）をこの順に施し、得られる冷間圧延板からドーナツ状板を打抜き、前記ドーナツ状板を加圧焼鈍するアルミニウム合金製ブランク材の製造方法において、前記冷間圧延における最終中間焼鈍を４５０℃〜５５０℃の温度で２時間〜１０時間施し、冷間圧延率を５％〜５５％とし、前記加圧焼鈍を３５０℃〜４００℃の温度で２時間〜２０時間施すことを特徴とするメモリーディスク用アルミニウム合金製ブランク材の製造方法である。
【０００５】
請求項２記載発明は、前記請求項１記載の製造方法により製造されたブランク材であって、加圧焼鈍後の平均結晶粒径が６０μｍを超え１５０μｍ以下であることを特徴とするメモリーディスク用アルミニウム合金製ブランク材である。
【０００６】
【発明の実施の形態】
請求項１記載発明は、冷間圧延における最終中間焼鈍条件および前記最終中間焼鈍後の圧延率を規定することにより、打抜加工後のドーナツ状板のダレを小さくし、前記最終中間焼鈍条件および圧延率に加えて、加圧焼鈍条件を規定して研削加工後における表面うねりを小さくしたメモリーディスク用アルミニウム合金製ブランク材の製造方法である。
【０００７】
この発明において、アルミニウム合金には、Ａｌ−Ｍｇ系合金（ＪＩＳ５０００系合金）などが主に使用される。冷間圧延板は、ＤＣ法などにより製造されるアルミニウム合金鋳塊に、ソーキング、熱間圧延、冷間圧延（中間焼鈍含む）をこの順に施す常法により製造される。前記冷間圧延板からのドーナツ状板の打抜きにはプレス打抜きなどの任意の方法が適用される。
【０００８】
この発明において、前記冷間圧延における最終中間焼鈍を４５０℃〜５５０℃の温度で２時間〜１０時間施し、冷間圧延率を５％〜５５％とする理由は、最終中間焼鈍条件が上限値を超えても、また冷間圧延率が下限値未満でも、ドーナツ状板のダレを十分小さくできないためであり、最終中間焼鈍条件が下限値未満でも、また冷間圧延率が上限値を超えても、加圧焼鈍後におけるブランク材の強度が高くなり、その後の研削加工での加工速度を速くできなくなり、研削加工後に表面うねりが生じるためである。最終中間焼鈍後の圧延率は７％〜５５％が特に望ましい。
【０００９】
また前記加圧焼鈍条件を３５０℃〜４００℃の温度で２時間〜２０時間に規定する理由は、前記温度、時間のいずれが下限値未満でもブランク材の強度が高くなりすぎて研削加工速度を速くできず、研削加工後に表面うねりが生じるためである。また、前記温度、時間のいずれが上限値を超えてもブランク材が軟質となり、研削加工時に砥石が目詰まりし易くなるためである。
【００１０】
請求項２記載発明は、前記請求項１記載発明で製造された加圧焼鈍後のブランク材であって、その平均結晶粒径が６０μｍを超え１５０μｍ以下のものである。この発明において、前記平均結晶粒径を６０μｍを超え１５０μｍ以下に規定する理由は、前記平均結晶粒径が６０μｍ以下のブランク材は強度が高いため研削加工速度を速くできず、その結果、研削加工後に表面うねりが生じるためである。一方、平均結晶粒径が１５０μｍを超えると軟質となり、研削加工時に砥石が目詰まりし易くなり、砥石の交換に時間が掛かり生産性が低下するためである。
【００１１】
【実施例】
以下に、本発明を実施例により詳細に説明する。
（実施例１）
Ａｌ−Ｍｇ系合金（古河電気工業（株）製のＦＰ−３）を常法により溶解鋳造して鋳塊とし、これをソーキング後、熱間圧延し、次いで冷間圧延してアルミニウム合金板とし、次いでこのアルミニウム合金板からドーナツ状板をプレス打抜きし、このドーナツ状板の内外径を面取り加工したのち、これを複数枚積層し、この積層体を治具により４０ｋｇの力で締め付けて加圧焼鈍してブランク材を製造した。前記最終中間焼鈍条件、前記最終中間焼鈍後の圧延率および加圧焼鈍条件は本発明規定値内で種々に変化させた。
【００１２】
（比較例１）
前記最終中間焼鈍条件、最終中間焼鈍後の圧延率および加圧焼鈍条件を本発明規定値外で種々に変化させた他は、実施例１と同じ方法によりブランク材を製造した。
【００１３】
実施例１および比較例１で製造した各々のブランク材について平均結晶粒径を調べた。また前記ブランク材を研削加工し、研削加工後の表面うねりの大きさを調べた。前記研削加工時の砥石の目詰まりも調べた。打抜加工後のドーナツ状板については、その端部のダレの大きさを測定した。ブランク材の平均結晶粒径はＪＩＳＨ０５０１に準じて測定した。
研削加工は、システム精工社製１１．５Ｂ研削機を用い、砥石に日本特殊研砥社製４０００番のＰＶＡ砥石を用いて行った。その際の研削速度、砥石寿命を表１に記す。研削速度は、砥石の面だし後、２０バッチ連続加工し、その後、５０μｍを研削するのに要した時間を測定して算出した。砥石寿命は、砥石が徐々に目詰まりし、研削速度が１０μｍ／ｍｉｎに低下したときまでに加工できたバッチ数で表した。表面うねりは、ＪＩＳＢ０６１０（“ろ波うねり曲線”の項参照）に基づいて調べた。Ｗ_ＣＡ（中心線うねり）の値が１０．０Å（１．０×１０^−３μｍ）以下は良好、１０．０Å（１．０×１０^−３μｍ）を超えたら不良と判定した。打抜加工性は、ダレ量ｕを光学顕微鏡を用いた焦点深度法により測定し、ｕの値が０．９５ｍｍ以下は打抜加工性が良好、０．９５ｍｍを超えたら不良と判定した。測定結果を表１に記す。
【００１４】
【表１】

【００１５】
表１から明らかなように、本発明方法により製造したＮｏ．１〜７のブランク材は、いずれも結晶粒径が６０μｍを超え１５０μｍ以下の範囲内にあり、研削速度、砥石寿命とも優れ、研削後における表面うねりが小さく、またプレス打抜後のドーナツ状板の端部のダレも小さかった。このうちＮｏ．７は加圧焼鈍を低温短時間施したため表面うねりが高めになり、Ｎｏ．４は加圧焼鈍を高温長時間施したため砥石寿命が短めとなった。但し、いずれも実用上差し支えない程度であった。
一方、比較例のＮｏ．８は冷間圧延率が低かったため結晶粒径が１５０μｍを超え、軟質であり、砥石の目詰まりが激しく砥石寿命が低下し、またドーナツ板のダレも大きかった。Ｎｏ．９は冷間圧延率が高かったため結晶粒径が６０μｍ以下となり、強度が高く、そのため研削加工速度が低下し、その結果、研削加工後に表面うねりが生じた。
【００１６】
【発明の効果】
以上に説明したように、本発明の製造方法では、冷間圧延における最終中間焼鈍条件並びに前記最終中間焼鈍後の冷間圧延率を適正に規定するので、冷間圧延板を打抜いて得られるドーナツ板はダレが小さく生産性に優れる、また前記規定に加えて加圧焼鈍条件を適正に規定するのでブランク材の強度が適当になり、研削加工が高速で行え、研削加工後のブランク材は表面うねりが小さい。従って、本発明方法により製造されるブランク材はハードディスクの高容量化に十分対応でき、また硬さが適当で研削砥石が目詰まりし難く生産性に優れる。依って、工業上顕著な効果を奏する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an aluminum alloy blank for a memory disk, which is a storage medium for a computer, and an aluminum alloy blank for a memory disk manufactured by the manufacturing method.
[0002]
[Prior art]
The blank material made of an aluminum alloy is manufactured by chamfering a donut-shaped plate press-punched from a cold rolled plate of an aluminum alloy, laminating a plurality of sheets, and subjecting them to pressure annealing. The blank material after this pressure annealing is then processed into a hard disk through each process of grinding, Ni-P plating, surface polishing, media processing (forming a storage medium on the surface), and incorporated into the hard disk drive. . The media processing is performed by a method such as texture or sputtering. By the way, the storage capacity of a 3.5-inch hard disk has increased from 10 GB to 40 GB in the past year, and it is expected that the capacity will be further increased in the future. In order to increase the capacity, it is necessary to form a storage medium in an orderly manner on the surface of the blank material during media processing. For this purpose, the blank material is required to have a small surface waviness after grinding. .
[0003]
[Problems to be solved by the invention]
However, in the conventional manufacturing method, (1) sagging occurs at the end of the doughnut-shaped plate after punching and it takes time for chamfering, and (2) surface waviness occurs in the blank material after grinding. There was a problem.
In view of the above, the present inventors examined a solution to the above problem, and the problem of (1) described above is by defining the final intermediate annealing conditions in cold rolling and the rolling rate after the final intermediate annealing. In addition, in addition to the final intermediate annealing condition and rolling ratio, the problem of (2) is found to be solved by defining the pressure annealing condition, and further investigations are made based on this knowledge and the present invention is repeated. It came to complete. An object of the present invention is to provide a method for manufacturing an aluminum alloy blank material for a memory disk that is less likely to sag in a doughnut-shaped plate after punching and has a small surface waviness after grinding, and a memory disk manufactured by the above-described manufacturing method. The object is to provide an aluminum alloy blank.
[0004]
[Means for Solving the Problems]
The invention according to claim 1 is a method in which soaking, hot rolling, cold rolling (including intermediate annealing) is performed in this order on an Al-Mg alloy ingot, a doughnut-shaped plate is punched from the obtained cold rolled plate, and the donut In the manufacturing method of the aluminum alloy blank material for pressure annealing the shaped plate, the final intermediate annealing in the cold rolling is performed at a temperature of 450 ° C. to 550 ° C. for 2 hours to 10 hours, and the cold rolling rate is 5% to 55%. %, And the pressure annealing is performed at a temperature of 350 ° C. to 400 ° C. for 2 hours to 20 hours.
[0005]
A second aspect of the present invention is a blank material manufactured by the manufacturing method according to the first aspect, wherein the average crystal grain size after pressure annealing is more than 60 μm and not more than 150 μm. This is an aluminum alloy blank.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 reduces the sagging of the donut-shaped plate after punching by defining the final intermediate annealing condition in cold rolling and the rolling rate after the final intermediate annealing, and the final intermediate annealing condition and This is a method for producing an aluminum alloy blank material for a memory disk in which, in addition to the rolling rate, a pressure annealing condition is defined to reduce surface waviness after grinding.
[0007]
In the present invention, as the aluminum alloy, an Al—Mg alloy (JIS 5000 alloy) or the like is mainly used. The cold-rolled sheet is manufactured by a conventional method in which soaking, hot rolling, and cold rolling (including intermediate annealing) are performed in this order on an aluminum alloy ingot manufactured by the DC method or the like. Arbitrary methods, such as press punching, are applied for the punching of the donut-shaped board from the cold-rolled board.
[0008]
In the present invention, the final intermediate annealing in the cold rolling is performed at a temperature of 450 ° C. to 550 ° C. for 2 hours to 10 hours, and the cold rolling rate is 5% to 55%. Even if the cold rolling rate is less than the lower limit, the sagging of the doughnut-shaped plate cannot be made sufficiently small, even if the final intermediate annealing condition is less than the lower limit, and the cold rolling rate exceeds the upper limit. This is because the strength of the blank material after the pressure annealing is increased, the processing speed in the subsequent grinding process cannot be increased, and surface waviness occurs after the grinding process. The rolling rate after final intermediate annealing is particularly preferably 7% to 55%.
[0009]
Moreover, the reason for prescribing the pressure annealing condition at a temperature of 350 ° C. to 400 ° C. for 2 hours to 20 hours is that the strength of the blank material becomes too high even if any of the temperature and time is less than the lower limit value, and the grinding speed is increased. This is because it cannot be fast and surface waviness occurs after grinding. Moreover, even if any of the said temperature and time exceeds an upper limit, it is because a blank material becomes soft and it becomes easy to clog a grindstone at the time of grinding.
[0010]
A second aspect of the present invention is a blank material after pressure annealing produced in the first aspect of the present invention, the average crystal grain size of which exceeds 60 μm and is 150 μm or less. In this invention, the reason why the average crystal grain size is defined to be more than 60 μm and 150 μm or less is that the blank material having the average crystal grain size of 60 μm or less has high strength, so that the grinding speed cannot be increased. This is because surface waviness occurs later. On the other hand, when the average crystal grain size exceeds 150 μm, the grindstone is easily clogged during grinding, and it takes time to replace the grindstone, resulting in a decrease in productivity.
[0011]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
An Al-Mg alloy (FP-3 manufactured by Furukawa Electric Co., Ltd.) is melt cast by a conventional method to form an ingot, which is soaked, hot-rolled, and then cold-rolled to obtain an aluminum alloy plate. Next, a donut-shaped plate is press-punched from this aluminum alloy plate, and the inner and outer diameters of this donut-shaped plate are chamfered, and a plurality of these are laminated, and this laminate is pressed with a jig with a force of 40 kg and pressed. A blank was manufactured by annealing. The final intermediate annealing conditions, the rolling ratio after the final intermediate annealing, and the pressure annealing conditions were variously changed within the specified values of the present invention.
[0012]
(Comparative Example 1)
A blank was manufactured in the same manner as in Example 1 except that the final intermediate annealing conditions, the rolling ratio after the final intermediate annealing, and the pressure annealing conditions were variously changed outside the specified values of the present invention.
[0013]
The average crystal grain size of each blank material produced in Example 1 and Comparative Example 1 was examined. Moreover, the blank material was ground and the size of the surface waviness after grinding was examined. The clogging of the grindstone during the grinding process was also examined. About the doughnut-shaped board after a punching process, the magnitude | size of the sagging of the edge part was measured. The average crystal grain size of the blank was measured according to JIS H 0501.
Grinding was carried out using a 11.5B grinding machine manufactured by System Seiko Co., Ltd., and using a No. 4000 PVA grinding wheel manufactured by NIPPON SPECIAL ENGINEERING CO., LTD. Table 1 shows the grinding speed and wheel life at that time. The grinding speed was calculated by measuring the time required for grinding 20 batches after grinding the grindstone and then grinding 50 μm. The wheel life was expressed as the number of batches that could be processed by the time when the wheel was gradually clogged and the grinding speed was reduced to 10 μm / min. The surface waviness was examined based on JIS B 0610 (refer to the section of “Wave wave waviness curve”). W _CA value is 10.0Å (1.0 × ^{10 -3} μm) of (center line waviness) following good was judged to be defective Once beyond the ^{10.0Å (1.0 × 10 -3 μm)} . The punching workability was measured by measuring the sagging amount u by a depth of focus method using an optical microscope. When the value of u was 0.95 mm or less, the punching workability was good, and when it exceeded 0.95 mm, it was judged as defective. The measurement results are shown in Table 1.
[0014]
[Table 1]

[0015]
As is apparent from Table 1, No. 1 produced by the method of the present invention. Each of the blank materials 1 to 7 has a crystal grain size in the range of more than 60 μm and 150 μm or less, excellent grinding speed and wheel life, small surface waviness after grinding, and donut-shaped plate after press punching The sagging at the end of was also small. Of these, No. No. 7 was subjected to pressure annealing for a short time at a low temperature, so the surface waviness was increased. No. 4 was subjected to pressure annealing at a high temperature for a long time, so that the grinding wheel life was shortened. However, all were practically acceptable.
On the other hand, no. In No. 8, the cold rolling rate was low, so the crystal grain size exceeded 150 μm, and it was soft, the clogging of the grindstone was severely shortened, and the sagging of the donut plate was also large. No. Since No. 9 had a high cold rolling rate, the crystal grain size became 60 μm or less, and the strength was high. Therefore, the grinding speed decreased, and as a result, surface waviness occurred after grinding.
[0016]
【The invention's effect】
As explained above, in the production method of the present invention, the final intermediate annealing conditions in cold rolling and the cold rolling rate after the final intermediate annealing are properly defined, so that it is obtained by punching a cold rolled sheet. The donut plate is small and excellent in productivity, and in addition to the above regulations, the pressure annealing conditions are properly defined, so the strength of the blank material is appropriate, grinding can be performed at high speed, and the blank material after grinding is Small surface waviness. Therefore, the blank material manufactured by the method of the present invention can sufficiently cope with the increase in capacity of the hard disk, has an appropriate hardness, is difficult to clog the grinding wheel, and is excellent in productivity. Therefore, there is an industrially significant effect.

Claims

The soaking, hot rolling, and cold rolling (including intermediate annealing) are performed in this order on the Al—Mg alloy ingot, the doughnut-shaped plate is punched from the obtained cold-rolled plate, and the donut-shaped plate is pressure-annealed. In the manufacturing method of the aluminum alloy blank material, the final intermediate annealing in the cold rolling is performed at a temperature of 450 ° C. to 550 ° C. for 2 hours to 10 hours, the cold rolling rate is 5% to 55%, and the pressure annealing is performed. Is performed at a temperature of 350 ° C. to 400 ° C. for 2 hours to 20 hours, and a method for producing an aluminum alloy blank for a memory disk.

A blank material made of an aluminum alloy for a memory disk, wherein the blank material is manufactured by the manufacturing method according to claim 1 and has an average crystal grain size after pressure annealing of more than 60 µm and 150 µm or less.