Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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The Effects of Surface Oxidation Occurring during Delivery from an Annealing Furnace to a Water Bath on the Microstructure and Tensile Properties of TWIP Steel

소둔로에서 수욕으로 이송 중 발생한 표면 산화가 TWIP 강의 미세조직과 인장 성질에 미치는 영향

  • Oh, Seon-Keun (Department of Materials Science and Engineering, Yonsei University) ;
  • Lee, Young-Kook (Department of Materials Science and Engineering, Yonsei University)
  • 오선근 (연세대학교 신소재공학과) ;
  • 이영국 (연세대학교 신소재공학과)
  • Received : 2020.03.09
  • Accepted : 2020.03.18
  • Published : 2020.03.30
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Abstract

In the present study, we investigated whether the surface oxidation of C-bearing TWIP steel ℃curs in the air during specimen delivery from an annealing furnace to a water bath and how the microstructure and tensile properties are influenced by surface oxidation. A cold-rolled Fe-18Mn-0.6 (wt%) steel was exposed in the air for 5 s after annealing at various temperatures (750℃, 850℃ and 1000℃) for 10 min in a vacuum, and then water-quenched. For comparison, another specimen, which had been quartz-sealed in a vacuum, was annealed at 1000℃ for 10 min and immediately water-quenched without exposure to air. The 750℃ and 850℃-annealed specimens and the quartz-sealed specimen showed a γ-austenite single phase in the entire specimen due to negligible surface oxidation. However, the 1000℃-annealed specimen exhibited a dual-phase microstructure consisting of ε-martensite and γ-austenite at the sub-surface due to decarburization. Whereas the specimens without decarburization revealed high elongations of 70-80%, the decarburized specimen exhibited a low elongation of ~40%, indicating premature failure due to cracking inside the decarburized layer with ε-martensite and γ-austenite.

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References

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