| 摘要 |
PURPOSE:To detect the presence and position of the minute flaw not confirmable by naked eye on the surface of an object to be inspected, by applying a low m.p. substance containing a fluorescent substance or dyeing substance to the surface of the object to be inspected placed under a vacuum atmosphere in a liquid state and allowing said substance to penetrate in a flaw to solidify the same. CONSTITUTION:An object to be inspected composed of an SUS316HTB material, for example, having a precipitated sigma-phase 2 and having minute flaws 3 generated at the crystal grain boundaries thereof by thermal stress is placed under a vacuum atmosphere and polishing using a polishing disc is applied to the surface thereof and a liquid low m.p. substance (paraffin) 4 containing a fluorescent substance (Eosine) or a dyeing substance is applied to the finished surface and the vacuum atmosphere is returned to atmospheric pressure to allow the low m.p. substance 4 to sufficiently penetrate in minute flaws 3 and, thereafter, said substance 4 is solidified under natural cooling. Next, the surface is lightly polished or wipen to allow the low m.p. substance to remain only in the minute flaws 3 and irradiated with ultraviolet rays by an ultraviolet ray irradiation apparatus to be inspected by a light microscope. Whereupon, the minute flaws on the surface of the object to be inspected can be certainly detected as fluorescent images. When the dyeing substance is used, it is unnecessary irradiate the surface with ultraviolet rays and inspection becomes simple.
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