Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Effect of Fully and Semi Austempering Treament on the Fatigue Properties of Ductile Cast Iron

완전 및 부분 오스템퍼링 처리가 구상흑연주철의 피로특성에 미치는 영향

  • 임복규 (강원대학교 대학원 기계메카트로닉스공학과) ;
  • 황중각 (강원대학교 대학원 기계메카트로닉스공학과) ;
  • 김동열 (삼척대학교 기계메카트로닉스공학부) ;
  • 김민건 (강원대학교 기계메카트로닉스공학부)
  • Published : 2005.03.01
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Abstract

Single phase bainite structure which is obtained by the conventional austempering treatment reduces the ductility of ductile cast iron. Because of the reduction of ductility it is possible to worsen the fatigue properties. Therefore, semi austempered ductile iron which is treated from ${\alpha}+{\gamma}$ is prepared to investigate the static strength and fatigue properties in comparison with fully austempered ductile iron (is treated from ${\gamma}$). In spite of semi austempered ductile iron shows the $86{\%}$ increase of ductility. Also, semi austempered ductile iron shows the higher fatigue limit and lower fatigue crack growth rate as compared with fully austempered ductile iron. By the fractographical analysis, it is revealed that the ferrite obtained by semi austempering process brings about the plastic deformation(ductile striation) of crack tip and gives the prior path of crack propagation. The relatively low crack growth rate in semi austempered specimen is caused by above fractographical reasons.

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References

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