A smoker inlet pre-wire line, after eight years of use cracking failure, the central performance of the pipeline and elbow body cracks can not be welded, and welding cracks will expand in the elbow. Elbow material is 0Cr18Ni10Ti, working temperature between 0-700 °C, elbow internal circulation medium for flue gas. To study the failure of cracked pre-wired elbows at flue gas inlet, evidence and specimen collection, chemical composition analysis, chemical composition analysis, fracture analysis, metallographic analysis, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The experiments confirmed the reason for the cracked pre-wired elbows at flue gas inlet: Smoker inlet pre-wired elbow in the Cr element precipitation at the grain boundary, resulting in Cr-poor area, reducing the corrosion resistance of the material; flue gas impurities in the element S in the grain boundary enrichment, resulting in adsorptive dissolution at the grain boundary; in the case of a significant temperature difference, the use of eight years of pipeline ultimately cracked due to intergranular corrosion.