Steel samples from Buildings 1, 2 and 7 of the World Trade Center were collected during the Federal Emergency Management Agency forensic investigation shortly after the September 11, 2001 incident. Macroscopically, the steel samples supplied exhibited severe “erosion” with plate thickness varying from 12.7mm to a total loss of metal in many areas. Also, some localized plastic deformation was observed. A determination of the cause of this unexpected erosion and an estimate of the maximum temperature that this steel likely experienced are the subjects of this paper.
