Research On Damage Of Cracking Furnace Tube With Long-Term High Temperature

With the rapid development of modern industry, in the petrochemical plant, the high temperature furnace tube cracking furnace is used widely, in the long-term high-temperature environments, high temperature furnace tube cracking furnace damage, burst pipes prone to failure. Blast furnace tube cracking furnace tube failure not only to production units caused serious economic losses, more seriously, but also endanger the lives and property. Therefore, the high-temperature furnace tube cracking furnace safety and reliability of more and more widely appreciated.This thesis focuses on high-temperature injury of the cracking furnace tube for macro-fracture analysis, including analysis of surface topography on the fracture and damage parts of the mechanical properties of materials, from the macro to determine the preliminary nature of the fault. Meanwhile, after injury Cracking Furnace Tube has conducted the analysis of microstructure, including after injury to micro-cracking furnace tube fracture surface analysis and fracture surface composition analysis. Analyze its microstructure on the damage mechanism. Finally, this thesis after injury cracking furnace tube for recovery of heat treatment of the probe test, different temperature and different holding time and different cooling conditions of the last three constraints to explore the optimal recovery of heat treatment process.Finally, after testing the following conclusions: 353MA (25Cr-35Ni) cracking furnace tube the appearance of the fracture morphology of corrosion due to oxidation the color gray, smooth fracture surface, fracture of the color of white light, no cracks and the final instantaneous source Off region, typical of the overall fracture of brittle fracture. The impact toughness of the new pipe is high, the sample after impact is not completely disconnected, showing a very good plasticity, damage cracking furnace tube after the impact toughness is very low, the sample completely disconnected after impact, fracture without plastic Deformation, showing the characteristics of brittle fracture. After injury than the new furnace tube cracking furnace tube is much higher hardness, have shown a significant hardening material. New tube cracking furnace tube for the austenitic microstructure of the material in grain boundaries and the distribution of a small amount of granular carbide. The plastic is better, higher toughness, not prone to brittle fracture. Injury cracking tube material in the austenitic microstructure along the grain boundary on the basis of a large number of long strips of brittleσphase and eutectic carbide particles. Significantly reduce its toughness, brittleness increased. New Specimens after impact fracture morphology, showing a large number of dimples, and its morphology is characterized by plastic dimple morphology. After injury Cracking Furnace Tube fracture morphology, showing a steady pattern of rivers, and its morphology is characterized by brittle cleavage morphology. Transverse fracture surface of the main components of Cr and Fe oxides, high temperature oxidation occurred, but did not find S, Cl, and the presence of corrosive media elements. Longitudinal fracture surface composed mainly of Cr, Ni and Fe, the basic ingredient found Ni-Cr-Si heat-resistant steel ASTM standards 353MA (25Cr-35Ni) in the ingredient. Furnace duct injury was not due to material composition, but rather brittle due to their organization In the heating temperature is 1140℃, holding time of 1 hour cases, 10% of the salt water through theσphase to eliminate the effect of quenching the best treatment from the injury without the occupied area ratio ofσphase particles down to 21.5% 35.8% , Is the condition, the experiment to explore the best out of the heat treatment method. Heat treatment process to explore the best out of a certain role in the elimination phase,σthe elimination phase can reach about 45% effective, but theσphase out by this study to explore the heat treatment process can not be completely eliminated.