| 摘要 |
PURPOSE:To obtain the title engine parts having high-cycle thermal fatigue strength and also low-cycle thermal fatigue strength by constituting the whole of engine parts made of Al alloy of a hardened part formed by means of T6 heat treatment and also constituting only a part, liable to cause low-cycle thermal fatigue, of the above hardened part of a tempered softened part. CONSTITUTION:The whole of parts made of Al alloy formed by casting is subjected to T6 heat treatment, by which a hardened part is formed. Further, only a part, in the above hardened part, requiring low-cycle thermal fatigue strength is tempered at a temp. higher by >=10 deg.C than the maximum engine operating temp., by which a softened part in a state free from T6 heat treatment is formed. As a result, the hardened part in the T6 heat treated state has high- cycle thermal fatigue strength, and on the other hand, the above softened part in the state free from T6 heat treatment has low-cycle thermal fatigue strength. |
