C-Mn steel is heavily utilized in the oil and gas industry, primarily in upstream operations and downstream refining. Many of these vessels are exposed to wet hydrogen sulfide environments and as a
consequence become damaged. Assessment of these damaged vessels is a key point for continued safe operations. This paper addresses several of the key material properties of C-Mn steels required to perform such assessments. Guidelines on the influence of welding, stress relief treatments, crack location and hydrogen charging on the mechanical properties and fracture toughness are detailed. Results showed elongation and reduction in area were greatly affected by hydrogen charging, however, yield and tensile strength were only mildly affected. Regarding toughness, the parent metal and heat affected regions of hydrogen charged material exhibited a factor of three decrease in toughness compared to baseline values, while the toughness of the weld metal remained relatively unchanged.
Keywords: fitness-for-service, mechanical properties, fracture toughness, carbon steel, hydrogen induced cracking, HIC, sulfide stress cracking, SSC, sour service, hydrogen sulfide, H23, welding