Application of magnetic analyzers for detecting carburization of pyrolysis furnace tubes

Ethylene pyrolysis furnace is a key equipment in the ethylene production industry with the pyrolysis furnace tube being the core component of the system. The tube operates at high temperature (950?-1,100?) and hydrocarbon medium for a long time, and the Cr35Ni45Nb centrifugal casting alloy material is often chosen as the material of the tube. Due to its harsh working conditions, its common failure issues include carburization, high-temperature creep cracking, thermal shock and thermal fatigue, overheating, creep expansion, bending, etc. Among them, carburization is the main cause of furnace tube failure. In this work, based on the characteristics of HP series (ASTM HP grade) furnace tube material, which is transformed from paramagnetic material to ferromagnetic material following carburization, the cracking furnace tube with different carburization layer thickness has been prepared, and the coercivity of furnace tube with different thickness of carburization layer is tested by magnetic analyzer. The relationship curve between carburization layer thickness and coercivity is subsequently studied to find a means to test the carburization layer thickness in engineering. By fitting the experimental data, the fitting rate reached 97%, which in turn verified the validity and accuracy of the method.

Automated summary

Ethylene pyrolysis furnace, a crucial equipment in the ethylene production industry, relies on the pyrolysis furnace tube as its core component. The tube, made of Cr35Ni45Nb centrifugal casting alloy material, operates under high temperature and hydrocarbon medium for prolonged periods. Common failure issues include carburization, high-temperature creep cracking, thermal shock and fatigue, overheating, creep expansion, and bending. Carburization is identified as the primary cause of furnace tube failure. This study focuses on the carburization layer thickness of HP series (ASTM HP grade) furnace tube material and tests the coercivity of tubes with varying carburization layer thickness using a magnetic analyzer. The relationship between carburization layer thickness and coercivity is analyzed to develop an engineering method for testing carburization layer thickness. The fitting of experimental data achieved a 97% accuracy rate, confirming the validity and accuracy of the method.