| 摘要 |
PURPOSE:To obtain a disk substrate without expanding and recessing of the central part of the substrate and without waving at a micropitch by forming the substrate without rough finishing unlike in the conventional embodiment. CONSTITUTION:The major difference from the conventional embodiment lies in that the rough finishing of a blank surface is eliminated from the process for producing the substrate. The sheet material worked by cold rolling has generally overall surface waving on account of the process for manufacture, but is finished extremely precisely in the thickness size and surface roughness. The aluminum alloy substrate after cold rolling is worked to, for example, 1.96mm. which is the thickness after the rough finishing in the conventional embodiment. The inside and outside peripheral surfaces of the blank formed by press working in the process 1 are finished in the process 2 and thereafter plural sheets are superposed and are thermally straightened in the process 4 without rough finishing; thereafter, the substrate is subjected to the same process as in the conventional embodiment.
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