New research uncovers how steel fails at high temperatures, like those in the World Trade Center seven years ago — or in the fusion reactors of tomorrow:
The key advance is the understanding that, at high temperatures, tiny irregularities in a steel’s structure can disrupt its internal magnetic fields, making the rigid metal soft.“Steels melt at about 1,150C (2,102F), but lose strength at much lower temperatures,” explained Dr Sergei Dudarev, principal scientist at the United Kingdom Atomic Energy Authority (UKAEA).
At room temperature, the magnetic fields between iron atoms remain regular, but when heated, these fields are altered allowing the atoms to slide past each other, weakening the steel.
“[The steel] becomes very soft. It is not melting but the effect is the same,” said Dr Dudarev.
He said blacksmiths had exploited this property for hundreds of years – it allows iron to become pliable at temperatures much lower than its melting point.
The peak in this pliability is at 911.5C, but begins at much lower temperatures, at around 500C (932F) – a temperature often reached during building fires.