In Situ TEM and APT Analysis on the Dislocations Associated with Solute Carbons in Strain-Aged Low Carbon Pipeline Steels

Hyoung Seok Park; Ju Seok Kang; J.Y. Yoo; Chan Gyung Park

doi:10.4028/www.scientific.net/MSF.654-656.122

Paper Titles

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Study on Carbonitride Precipitating Process in Nb-V Micro-Alloyed Steel
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650°C Long-Term Structure Stability Study on 18Cr-9Ni-3CuNbN Heat-Resistant Steel
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In Situ TEM and APT Analysis on the Dislocations Associated with Solute Carbons in Strain-Aged Low Carbon Pipeline Steels
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In Situ Observation of Microstructure Evolution in Low Carbon Bainite Steels Isothermally Held Below A₁ Temperature
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Isothermal Martensitic Transformation in a Sensitized SUS304 Stainless Steel under Magnetic Field
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Microstructural Observation on Materials of the Japanese Sword under Fold-Forging Process
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Evidence of Lath Martensite in High-C Japanese Sword Produced from Tamahagane Steel by Tatara Process
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In Situ TEM and APT Analysis on the Dislocations Associated with Solute Carbons in Strain-Aged Low Carbon Pipeline Steels

Abstract:

Low carbon (~0.34 at.%) pipeline steels with high strength and high toughness are widely used for the transportation of petroleum and natural gas. These pipelines usually experience UOE (bending by U press, forming by O press, Expansion) piping followed by coating process at 250°C, which usually cause strain aging phenomenon with discontinuous yielding in service. In order to understand the major cause of the strain aging in these low carbon pipeline steels, the dislocations associated with solute carbon atoms have been investigated in three different types of steels (plate, pipe, and coated pipe). In-situ TEM heating up to 250°C for 30min did not cause any change of structure in both steel plate and pipe. However, APT results revealed the segregation of carbon atoms alone dislocation lines in ferrite region of both UOE pipes and coated pipes. It is believed that this solute segregation along the dislocations is the major cause in the case of strain aging of low carbon pipeline steels.