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Apparatuses for complex preparation and processing of hydrogen sulfide-containing natural gas are commonly produced from carbon steels of the 20Yuch type. However, the strength level of these steels is low (a0a > 240 N/mm2). Low-alloy weldable steel 09G2S has a higher strength, namely, a0_2 > 300 N/mm 2 for rolled stock up to 32 mm thick and g0a = 275 N/mm 2 for rolled stock up to 80 mm thick. At the same time, steel 09G2S has a low cold strength (the semibrittleness temperature 7"50 > -30~ and a low resistance to hydrogen sulfide cracking (the threshold stress ath = 0.6~o.2). The present paper is devoted to the effect of the composition and structure on the set of properties of new low-alloy plate steel 09GSNBTs, which possesses elevated strength and is resistant to hydrogen sulfide cracking.Cracking of low-alloy steel in a medium of moist natural gas containing hydrogen sulfide is caused by the presence of atomic hydrogen, which can easity permeate the steel, diffuse, and accumulate in places of stress concentration and on inclusion-matrix interfaces, creating conditions (weakening the interatomic binding forces, creating plane pressure, etc.) favorable for the initiation and development of cracks. It should be noted that cracks and blisters in steel are usually formed on phase boundaries of the matrix and manganese sulfides that have an elongated shape and also in places with an inhomogeneous structure caused by segregations of such elements as manganese and phosphorus. In the absence of an external load cracks appear in places where nonmetallic inclusions and structural inhomogeneities are accumulated and they propagate in the direction of rolling. In loaded parts cracks propagate normal to the direction of application of the loadThe aim of the present work consists in choosing a steel composition for parts operating in a hydrogen sulfide-containing medium and a regime of heat treatment that would ensure the specified level of strength characteristics and a high resistance to brittle fracture so that cracks initiated by the action of hydrogen would not develop. In order to eliminate localization of hydrogen on phase boundaries and formation of 45blisters and cracks contamination of the steel with nonmetallic inclusions (sulfides etc.) should be decreased, the remaining inclusions should be globularized, and the structural inhomogeneity in the axial zone should be decreased.In choosing the chemical composition for a low-alloy hydrogen sulfide-resistant steel with elevated strength we used microadditives of carbonitride-forming elements, namely, niobium and zirconium, to break up the grains and strengthen the structure by disperse particles. In order to improve the toughness parameters of the matrix and strengthen the solid solution we introduced 0.5-1.0% Ni, 0.5-0.8% Cr at a diminished level of manganese (0.9-1.1%) [1,2]. For steel of this class it is important to attain a structure of granular pearlite, which is more resistant to hydrogen embrittlement than lamellar pearlite [3]. A negative effect is exerted...