Causes and Mechanisms of Fracture of a Main Line Section Made of 17G1S Steel

Abstract

Abstract—The cause and the mechanism of formation of a long crack in a linear oil-trunk pipeline section consisting of two longitudinal pipes 1220 mm in diameter made of low-alloy 17G1S steel are comprehensively studied. The length of the crack moving along the longitudinal weld exceeds 3 m. The chemical composition and the mechanical properties of the pipe metal are found to meet the requirements of standards, and the impact toughness at negative temperatures is slightly lower than the standard. The crack moved according to a fatigue mechanism with a predominant grove relief. The main causes of crack nucleation are as follows: a significant stress concentration near the inner weld with distorted geometry of the reinforcing beads and a cyclic character of loading the oil pipeline.