| 摘要 |
PURPOSE:To prevent the occurrence of breakage due to partial embritlement of a corner part after nitriding, by a method wherein, in a piston ring made of steel on which nitriding in a specified depth is applied, chamfering is applied on the corner part thereof throughout a range having a specified length. CONSTITUTION:In a piston 1 made of steel on which nitriding is applied in depth 9 of 100-200 mum, nitriding on a corner part is simulteneously progressed from the two directions of an upper surface 2 or an under surface 3 and an inner peripheral surface 4 or an outer peripheral surface 5. As a result, a nitriding layer 6 of the corner part has the nitriding depth 9 deeper than that of other nitriding layer, and has high nitrogen concentration, and is partially bristle. In order to cope with the above, chamfering having size of 0.15-0.6 mm is applied on the corner part. In this case, a chamfering shape is, for example, an R-shape. (a) is the chamfering size of the upper surface side or the under surface side, and (b) is the chamfering size of the inner peripheral side or the outer peripheral side.
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