Failure Analysis of Coil in Convection Chamber in Pyrolyzer of Ethylene

By means of macroscopical rupture analysis, chemical composition analysis, fracture surface SEM analysis and metallographic structure analysis, the cracking reason of coils in convection chamber in ethylene cracking furnace was analyzed. The results showed that the sensitization of heat affect zone (HAZ) of 304H stainless steel joint resulted in the degradation of the resistance to corrosion. Stress corrosion cracking (SCC) in HAZ of the joint happened with the combined action of sodium hydroxide, Cl- and welding residual stress.