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Vol.35, No.11, 1484 ~ 1492, 1997
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| Title |
| Microstructural Influence on the Fatigue Properties of High Strength Spring Steels |
| 이기안 , 남원종 , 유선준 , 최해창 , 이종수 K . A . Lee , W . J . Nam , S . J . Yoo , H . C . Choi , C . S . Lee |
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| Abstract |
| The high cycle fatigue properties of a high strength spring steel have been investigated in relation to the microstructural variation through austenzing followed by tempering at different temperatures. The rotating bending fatigue and fatigue crack growth (FCG) tests were carried out and a transmission electron microscope equipped with an energy dispersive X-ray unit was used to characterize the precipitates behavior. The results indicate that the fatigue endurance (σ_f) increases with increasing tempering temperature, reaching a maximum at 450℃, then decreases at 500℃. The increase of σ_f is mainly attributed to the refined distribution of precipitation, together with the structural uniformity of tempered martensite. The inhomogeneity of tempered martensite due to excessive precipitation acounts for the decrease of σ_f, at 500℃. By contrast, the FCG results show an insensitivity of the stage-II growth behavior to the microstructural changes for the whole range of tempering temperature tested. The insensitivity is interpreted in terms of the counterbalancing microstructure-dependent contributions to the FCG, behavior. |
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