2011 Volume 60 Issue 4 Pages 190-195
Hydrogen embrittlement phenomena and recent developments of low alloy steel high strength Oil Country Tubular Goods (OCTG) and linepipes are reviewed.
In oil and gas fields, Sulfide Stress Cracking (SSC), which is caused by hydrogen absorption from H2S containing (sour) environments and applied tensile stress, is a major problem for high strength OCTG. Various metallurgical improvements had been tried to improve SSC resistance of high strength OCTG. In 1990's, 110 ksi (YS 758 MPa) grade sour resistant OCTG was developed by grain refinement and reduction in segregation elements such as P, S and Mn. In 2000's, 125 ksi (YS 862 MPa) grade sour resistant high strength OCTG was developed by inclusion refinement, decrease in dislocation density and control of carbides morphologies.
Hydrogen Induced Cracking (HIC), which occurs in both high strength and low strength steels without applied stress, is a major problem for linepipes. HIC occurs and propagates along elongated inclusions such as MnS or center segregated hardened portion of steel plate. 65 ksi (YS 448 MPa) grade sour resistant linepipes are widely commercialized by inclusion spheroidization and prevention of segregation through Thermo Mechanical Controlled Process (TMCP). Furthermore, 70 ksi (YS 483 MPa) grade sour resistant linepipes are developed by a progress in above mentioned techniques recently.
