The causes and character of the fracture of a section cut from a main gas pipeline 530 mm in diameter made of low-alloy 17GS steel have been investigated. The length of a longitudinal main crack in the base metal is 12 m. The gas pipeline failed due to stress corrosion cracking according to a hydrogen mechanism. Cracks originated on the outer surface of the pipe near corrosion pits. Preferred crack propagation along the boundaries of ferrite grains and pearlite colonies is revealed. The fraction of intergranular fracture is 6–9.5%. An anomalously high anisotropy of impact toughness is found in the place of plastic corrugation formation, K _a = 3.2–3.9.

中文翻译：

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由低合金17GS钢制成的直径530毫米的主管道的断裂

研究了由低合金17GS钢制成的直径530 mm的主煤气管道上切下的截面的断裂原因和特征。母材中的纵向主裂纹的长度为12 m。气体管道由于氢机制的应力腐蚀开裂而失效。裂纹起源于腐蚀坑附近的管道外表面。揭示了沿铁素体晶粒和珠光体菌落边界的优选裂纹扩展。晶间骨折的比例为6-9.5％。在塑料波纹形成的位置发现了异常高的冲击韧性各向异性， K _a = 3.2–3.9。