Abstract: A cracking and leakage incident occurred in a de-methanizer reboiler pipeline. This article presents the chemical composition analysis, hardness testing, metallographic examination, fracture microscopic morphology, and scale component analysis of both the base metal and weld joints of the failed pipeline. The results indicate that the primary cause of the pipeline cracking was the high carbon content in the raw material, which led to carbide precipitation during the welding process. Additionally, intergranular corrosion occurred under the influence of the corrosive medium.