Hydrogen production reformer furnace tubes made of cast austenitic alloy steels serve in the temperature range of 1073—1173 K and pressure around 3—4 MPa. Though the design life is about 100000 h

premature failures within 3—8 years are more common

mainly caused by premature creep induced by overheating. The cast tube material undergoes microstructural changes with service exposure and as a consequence

degradation in strength. The methods of macro inspection

chemical analysis

microstructure

scanning electron microscope and mechanical properties testing were used to analyze on the rupture HP40Nb steel tubes from a hydrogen production reformer furnace of one petroleum company when they were used only 18 h during the test run.The rupture life was very short and needed to find the reason

in case the similar incidents. The results show that the reason of failure for the furnace tubes is high temperature creep rupture and over temperature seriously is the direct reason.