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The slow strain rate test was used to study the effect of a number of corrosive soil electrolyte components and corrosion inhibitors on the liability of pipe steel X70 to stress corrosion cracking in weakly acidic and neutral media simulating the electrolyte under delaminated coatings on underground pipelines. The electrochemical behavior of X70 pipe steel in the presence of some corrosion inhibitors was studied. It was shown that inhibitors of metal anodic dissolution can considerably improve the cracking resistance of pipe steel.

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Low carbon ferrite-bainite pipe steels of the K65 (Kh80) strength grade produced by two manu facturing companies have been studied using different mechanical tests and fractographic analysis of frac tured surfaces. The results demonstrate that the energy capacity a (a c ) and the true relative reduction at frac ture ϕ f upon tensile tests, as well as the level of KCV -40 ≥ 250 J/cm 2 and the relative width of the zone of homo geneous ductile fracture L C /B at the fracture surface of Charpy samples upon impact bending tests, can be used as the laboratory criteria of crack resistance.

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Abstract-The structure and mechanical properties of the technological welded joints of large diameter pipes of strength class K60 produced by two companies are studied. Along with standard mechanical proper ties (σ 0.2 , σ u , δ, ψ), specific work of deformation a (tensile toughness) and true rupture strength S f are esti mated from an analysis of the stress-strain diagrams constructed in true coordinates. The mechanical behav ior is found to be different for samples cut from different zones of a welded joint (central weld, heat affected zone, and base metal). The mutual correlation between parameters a, S f , and impact toughness KCV is con sidered.