Abstract: Brittle bursting occurred in 20 carbon steel pipe of diesel hydrogenation recycling in a chemical plant. The pipe debris was treated by stress relief annealing and dehydrogenation treatment, respectively. By comparing the microstructure and mechanical properties of the treated debris with those of the untreated original debris, as well as combination with chemical composition detection and fracture morphology observation, the cause of the pipe bursting was analyzed. The results show that strain-age embrittlement occurred in the pipe material after a long period of service, leading to brittle bursting of the pipe. The relatively high nitrogen content in the pipe material and the large deformation of the grains were the main reasons for strain-age embrittlement.