Failure of a continuous-annealing furnace roller at Mobarakeh Steel Company

In this study, a failure analysis of an austenitic G-40CrNiSi25-12 steel furnace roller was performed by using chemical analysis, metallographic examination, Vickers micro-hardness measurements, X-ray diffractometer analysis and investigation of the crack propagation path in failed samples of the roller metal. The examination results revealed that roller fracture was caused by precipitation of the sigma phase during prolonged heating at temperatures exceeding 650 °C, resulting in a detrimental decrease in steel toughness at lower temperatures occurring during shut-down, straightening or heating-up periods.