Journal of Korea Foundry Society (한국주조공학회지)

Korea Foundry Society (한국주조공학회)
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The Influence of [Mn/S] Ratios on the Fracture Morphology of a Heavy-section Steel Castings at Elevated Temperature

대형주강의 고온파단형태에 미치는 [Mn/S]비의 영향

  • Kim, Sung-Gyoo (Department of Materials System Engineering, Pukyung National University) ;
  • Kim, Ji-Tae (Samyoung M-Tek Co., Ltd.) ;
  • Park, Bong-Gyu (Department of Materials System Engineering, Pukyung National University) ;
  • Park, Heung-Il (Department of Materials System Engineering, Pukyung National University)
  • 김성규 (부경대학교 신소재시스템공학과) ;
  • 김지태 ((주)삼영엠텍) ;
  • 박봉규 (부경대학교 신소재시스템공학과) ;
  • 박흥일 (부경대학교 신소재시스템공학과)
  • Received : 2014.07.02
  • Accepted : 2014.10.19
  • Published : 2014.10.31
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Abstract

Using the Gleeble test, the effects of [Mn/S] ratios and the presence of sulfides on the high-temperature fracture morphology of heavy-section steel castings were analysed via the observations of the microstructures. The specimens for which the [Mn/S] ratio was in the range of 60~80 showed a ductile fracture morphology with an area reduction of more than 60%, while some specimens with similar [Mn/S] ratios showed a brittle fracture morphology with an area reduction of 0.0% due to the liquidation of sulfides at the grain boundary. The fracture morphology was classified into three types in the Gleeble high-temperature tensile test specimens. The first type showed dimple formation at the grain boundary, the formation of globular MnS sulfides, and plastic deformation of sulfides at an elevated temperature, indicating a needle-point type of ductile fracture with area reductions of 96.0~97.8%. The second type was a knife-edge type brittle fracture with an area reduction of 0.0% due to the film-type liquidation of sulfides at the grain boundary, band-type liquidation, and the liquidation of a terraced nipple pattern. The third type was the typical ductile fracture with an area reduction of 31.3~81.0%, in accordance with the mixture of dimples with in the grains and terraced nipple pattern at the grain boundary.

Keywords

References

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