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Dr.ir. S.E. Offerman

Fire-resitant steel

"Collapsing buildings due to overheated steel a thing of the past"

Erik Offerman, Materials scientist


Materials scientist Erik Offerman is developing a fireresistant steel. He is studying whether by adding certain ingredients to steel he can prevent it from losing its strength when heated during a fire.

The dramatic images of the collapsing Twin Towers, approximately one hour after two aeroplanes had deliberately crashed into them, were the reason for Offerman to start his research. "The steel frame of the building was able to withstand the impact of the aeroplanes, but not the ensuing fire. This was reason for me to find out whether steel can be made intrinsically stronger to withstand high temperatures."

Crystals
"To develop fire-resistant steel you need to know exactly what happens to steel under high temperatures. I used an extremely high-powered X-ray microscope to study the steel's core after heating it in a special oven. I saw that the crystals in the steel become courser under different temperatures, which decreases the material's strength. I then sought ways of preventing this crystallisation.

Pickets
"The process of crystallisation could be stopped by adding certain elements to the steel. By adding a niobium compound, for example, 'pickets' are formed around the edges of the crystals at a temperature of about 600° Celsius. This chemical reaction peters out after a while, which is why you need to add various elements to the steel to ensure that it retains its strength over the entire temperature range from 550 to approximately 1200° Celsius - the maximum temperature of a fire. This is complex because interactions can also take place between all these elements."

Complex process
It is not enough simply to know what you need to add. You also need to know how fast the reactions proceed. After all, it is of no use whatsoever if the niobium compound only starts forming the pickets after three hours. You also need to find a way to manufacture the steel. In other words, it's a complex process. However, I have complete confidence that we will be able to produce fire-resistant steel in the near future, and that collapsing buildings due to overheated steel structures will be a thing of the past."

 

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