| Summary: | About a third reserves of the natural gas and oil contain H2S impurities, which, in the presence of moisture, form an acidic medium and can lead to pipeline destruction by the mechanisms of hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC). With the growing number of hydrocarbon fields being developed with a high content of H2S, the demand for gas and oil large diameter pipes grade from ВМS to Х70MS with high resistance to HIC and SSC increases. Comprehensive studies have been carried out in laboratory and industrial conditions to determine the effect of the chemical composition and thermomechanical processing on the microstructure, mechanical properties and resistance to HIC of rolled plates from low-alloy pipe steels. Optimal concentration of segregating elements (С ≤ 0.06%, Mn ≤ 1.00%), and schedules of accelerated cooling after controlled rolling (Тsc ≥ Ar3; Тfc = 520±30°C; Vc ≥ 20°C/с) provide the high resistance to destruction in H2S-containing media due the formation of a homogeneous microstructure without developed central segregation heterogeneity was determined. According to the research results, the technology for manufacturing of plates for large-diameter pipes grade X52MS, X56MS, X60MS, and X65MS ordered for sour service was developed.
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