| 摘要 |
PURPOSE:To improve resistance to fatigue of a bucket by holding the bucket for prescribed time within the temp. range where the lower limit is a specific temp. and the upper limit is the temp. for the structure of the base material to start austenite transformation and cooling quickly the curved surface in the jet inlet side region of the bucket until the ordinary temp. is restored. CONSTITUTION:A runner bucket consisting of a base material composed of an alloy steel and to receive the jet from a main nozzle of a Peltone wheel is held for prescribed time within the temp. range where the lower limit is 400 deg.C and the upper limit is the temp. for the structure of the base material composed of the alloy steel to start transformation to austenite. The curved surface in the jet inlet side region of the runner bucket is quickly cooled from the end period of the time when the bucket is maintained at said temp. until the ordinary temp. is restored. The resistance to fatigue of the bucket is thus improved while the reaction stress is allowed to remain. |
