Transactions of Materials Processing (소성∙가공)

The Korean Society for Technology of Plasticity and materials processing (한국소성∙가공학회)
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The Influence of Microstructure on the Bauschinger Effect in X80 Grade API Steel

X80급 API 강의 바우싱거 효과에 미치는 미세조직의 영향

  • 박재신 (포항공과대학교 신소재공학과) ;
  • 김대우 (포항공과대학교 신소재공학과) ;
  • 장영원 (포항공과대학교 신소재공학과)
  • Published : 2006.03.01
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Abstract

API steel is used for line-pipe to transport the oil and natural gas. As the recent trends in the development of API steel are towards the use of larger diameter and thicker plate, many researches have been studied to achieve higher strength, higher toughness and lower yield ratio in API steel. However, the strength of API steel after pipe forming is changed depending on the competition of the Bauschinger effect and work hardening which are affected by the strain history during pipe forming process. So, the purpose of this study is to investigate the influence of microstructure on the Bauschinger effect for API steel. To change the microstructure of API steel we have changed the hot rolling condition and the amounts of V and Cu addition. The compression-tensile test and the microstructure observation by OM and TEM were conducted to investigate the yield strength drop and the correlation between the Bauschinger effect and microstructure of API steel. The experimental results show that the increase of polygonal ferrites volume fraction increases the Baushcinger effect due to the back stress which comes from the increase of mobile dislocation density at polygonal ferrite interior during the compressive deformation. The hot rolling condition was more effective on the Bauschinger effect in API steel than the small amount of V and Cu addition.

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References

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Cited by

  1. Analysis and estimation of yield strength of API X80 linepipe steel pipe by low-cycle fatigue tests vol.18, pp.4, 2012, https://doi.org/10.1007/s12540-012-4005-z
  2. Effects of microstructure and pipe forming strain on yield strength before and after spiral pipe forming of API X70 and X80 linepipe steel sheets vol.573, 2013, https://doi.org/10.1016/j.msea.2013.02.050