Metals (Nov 2021)

Causes of Structural Heterogeneity in High-Strength OCTG Tubes and Minimizing Their Impact on Sulfide Stress Corrosion Cracking Resistance

  • Artem Davydov,
  • Andrey Zhitenev,
  • Alexey Alhimenko,
  • Natalya Devyaterikova,
  • Konstantin Laev

DOI
https://doi.org/10.3390/met11111843
Journal volume & issue
Vol. 11, no. 11
p. 1843

Abstract

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High-strength oil country tubular goods (OCTG) like C110, according to standard API 5CT (yield strength at least 758 MPa), are subject to requirements in terms of mechanical and corrosion properties. In this work, we studied the microstructure of seamless casing tubes made of class C110 high-strength steel with a 194.5 mm diameter and 19.7 mm wall thickness, and its influence on sulfide stress corrosion cracking (SSC). Casing tubes were obtained from continuous billets by screw piercing with preliminary quenching and tempering. It was shown that cracking during the tests always begins from the inner surface of the tube. Rough segregation bands were found on the inner tube surface, which occupies about a third of the thickness of the wall. To increase the resistance of 0.3C-Cr-Mn-Mo + 0.15(V + Nb + Ti) steel to SSC, primary recommendations for adjusting the chemical composition, production technology and heat treatment were developed.

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