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The causes of longitudinal crack in gas pipeline during pressure were analyzed by means of mechanical property test, microstructure analysis, sem analysis and energy spectrum analysis. The results show that the leakage of L415M spiral submerged arc welded pipe is caused by the contact between the base material of steel pipe and low-melting copper alloy in the process of high temperature, resulting in the brittleness of liquid metal. Specifically, when the leakage site of the steel pipe is heated at an abnormal high temperature, copper penetration along the grain boundary causes embrittlement, strength reduction and crack along the grain boundary, finally leading to the crack and leak of the steel pipe. |
