Metal deforming – With 'coating' of work – Metal coating
Patent
1987-10-27
1989-05-16
Larson, Lowell A.
Metal deforming
With 'coating' of work
Metal coating
72359, 72379, 360135, B21D 5300
Patent
active
048297992
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a method of economically and ultra-precisely manufacturing substrates for memory disks by performing a coining operation on the surfaces of a non-magnetic metal blank material having a non-magnetic metal coating as an underlayer, and more particularly, to a method of making the surfaces of a blank material very smooth and impressing a certain type of design (texture) on the surface of the blank material
Throughout the specification, the term "non-magnetic metallic substrate" is used to identify sheets or plates made of Al, an Al alloy, Cu, a Cu alloy, Mg, a Mg alloy, Ti, a Ti alloy or composites thereof. The term "non-magnetic metal as an underlayer" is used to identify a non-magnetic metal or alloy, a single body of metal such as Cr, etc. and an alloy such as a Ni-P alloy, a Ni-P-Cu alloy, a austenite stainless steel or the like.
PRIOR ART AND PROBLEMS THEREOF
Conventionally, substrates for magnetic memory disks which are used to record and reproduce letters, sounds and images, etc. have been produced by the following method. That is to say, a non-magnetic metal sheet for substrates, such as an aluminum alloy sheet is punched out to produce doughnut shaped blanks and the outer and inner diameters of the blanks are finished to predetermined dimensions with chamfers formed thereat for easy handling
Next, such surfaces of the metal blanks for the substrates are ultra-precisely finished (with respect to roughness and undulation, etc.) by such processes as machining by use of a diamond bit, polishing, grinding or combinations thereof.
The metallic substrates finished as above are covered with a non-magnetic metal coating as an underlayer in order to harden the surface thereof The underlayer, if it is coated chemically, is applied by means of plating approximately 20 .mu.m thickness of a Ni-P alloy or a Ni-P-Cu alloy. Afterwards, the plated surfaces are polished to obtain smooth surfaces A memory disk is made by applying a thin film magnetic media on the surfaces obtained as above and it is further provided with a protective coating as required (refer to FIG. 1).
However, in a flat and high density magnetic memory disk, there is a problem in that a magnetic head is adhered to the surfaces of the disk since the distance between the disk and the head is quite short and the surfaces of the disk add the head are flat It sometimes occurs that the head hits the disk surface, creating the problem of damaging the magnetic coating thereof Furthermore, there is a problem in regard to the magnetic characteristics.
For the reasons stated above, it has been the practice to provide a certain type of design (texture) on the surface of the disk on the underlayer (coated layer) and to apply a magnetic coating over the indented portions (refer to FIG. 2). The texture has conventionally been applied mechanically such as by a machining, or other mechanical methods such as by padding or using a pad or tape bearing grinding particles. As explained above, many operational steps have been required before providing the texture on the underlayer and the prior process thus required many facilities and considerable expenditure of time, thereby lowering productivity. Further, there has been a limitation as regards the texture design patterns that could be employed because they have been applied mechanically by using a pad or tape etc. bearing grinding particles. Further, there has been another drawback in that even when the texture pattern was applied to a plurality of disks under the same conditions, it has not been possible to obtain an identical design on each piece. Also, a rinsing operation was necessary because it was difficult to remove minute fragments generated during the operation of mechanically applying the texture pattern.
As explained above, while a memory disk having a textured surface is favorable in that it has excellent characteristics, there have been many drawbacks in manufacturing the same as well as in attempts to stabilize the quality of the same.
MEANS OF REM
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Coe Thomas U.
Krishnan Chris
Yamazaki Atsushi
C. Itoh & Co. Ltd.
Furukawa Aluminum Co., Ltd.
Kawasaki Steel Corp.
Larson Lowell A.
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