Stainless Steel and Fire Resistance
Stainless steel has many qualities that make it ideal as a construction material. One of these is its inherent oxidation resistance and continued strength at elevated temperatures. Austenitic stainless steel types tend to be the most useful but it is worth looking at ferritic and duplex types also, as embrittlement is not usually a practical issue due to the short-term nature of fires.
Stainless steels do not have an intrinsic ‘fire rating’ and so their fire resistance is tested on specific fabrications. These are carried out under extremely precise conditions and are covered fully by BS476 parts 20, 21 (load-bearing elements) and 22 (non-load-bearing elements). The behaviour of loaded stainless steel sections in a fire are automatically calculated using design software.
There is no possibility of ignition of stainless steels and flame spread is minimal, reducing the propagation of fire. The surface of the metal is inert and stable under oxidizing conditions, which are found in almost all flames and heat sources.
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Stewart Fraser Ltd. produce fire resistant doors and frames. Tests on their 316 fire resistant doors showed that after 60 minutes the temperature on the safe side of the door did not go above 98 degrees Celsius. After 2 hours and 10 minutes, the doors and frames were still fully intact and the test was terminated.
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Avesta AB tested 1.4362 (2304) type duplex as part of a clad ship’s bulkhead and found that the temperature on the safe side did not go above 30 degrees Celsius, even though the fire on the other side generated temperatures in excess of 1100 degrees Celsius and radiated with a bright orange glow.
The many different grades of stainless steel with fire resistant properties should be carefully considered. Though the austenitic family has lower conductivity than ferritic, containing heat flow through a structure, it is more prone to thermal distortion than the ferrites when thermal gradients are large.
To find out more details about the fire resistant properties of construction stainless steel, get in touch with our expert technical team today.