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The tendency towards strain ageing (SA) and hydrogenation (HD) of steel Kh80, manufactured by controlled rolling is studied. Fragments of pipes 1420 mm in diameter with a wall thickness of 18 mm are used for the study. It is established that SA for a metal pipe made of steel Kh80 leads to a reduction in ductility by 25%, and the critical brittleness temperature is increased by 35°C. During operation of steel Kh80 under the action of HD, the greatest embrittlement effect develops at -40°C.In domestic and world practice of pipeline construction, a tendency is noted towards an increase in the strength category for the steels used. Use of pipes made of high-strength steels will make it possible to increase the working pressure in pipelines without increasing the metal content of the structure and to reduce construction expenditure.Steels of strength categories Kh80 and Kh100 are considered as promising materials for use in the northern European and far eastern pipelines. Due to the optimum combination of alloying, and heat treatment, these steels exhibit not only high strength properties, but also high resistance to brittle failure [1].A considerable amount of work has been devoted to studying the structure, weldability, and mechanical properties of these steels [1][2][3][4]. However, in scientific and technical publications there is insufficient information about the possibility of providing metal mechanical property stability over the whole pipeline operating period. Damage of oil and gas pipelines may be due to development in pipe steels of strain ageing (SA) phenomena [5] and hydrogenation (HD) [6,7]. Ageing develops particularly intensely in steels prepared by controlled rolling [2].The aim of this work is to study the tendency towards SA and HD of high-strength pipe steel Kh80, prepared by controlled rolling.Fragments of pipe steel Kh80 1420 mm in diameter with a wall thickness of 18 mm of the following composition (%) were studied: 0.057 C, 0.16 Si, 1.74 Mn, 0.008 P, 0.004S, 0.14 Ni, 0.27 Mo, 0.034 Cr, 0.14 Cu, 0.032 Nb, 0.005 V, 0.011 Ti, and 0.002 Ca.The tendency of steel towards SA was studied in accordance with GOST 7268−82. Specimens were used with a size of 12 × 12 × 250 mm cut from pipe fragments that were subjected to 10% deformation and subsequent tempering at 250°C for 1 h.

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