The origin of the phrase, “Jet fuel can’t melt steel beams” is the widely renown argument used to suggest that the September 11 attacks were an ‘inside job’.
The Fallacy disproven
The Steel Fabrication Services community is known for disagreeing with the fallacy of this theory. While steel beams do not need to melt in order to lose their integrity, steel forges conventionally heat beams several hundred degrees above the temperature at which jet fuel burns. That being said, this question predicates a more pertinent subject pertaining to the heat resistance of steel beams.
Literature surrounding steel fabrication suggests that fire will almost certainly warp and twist steel, but this does not always follow that the strength of the steel is reduced.
It is an industry truism that steel which has been heated hot enough to undergo damaging, erosion, rapid temperature shifts, or grain coarsening, will inevitably suffer from disfigurement and distortion, resulting in a permanent dysfunctionality. However, those brands of steel will likely be filtered out within the factory and manufacturing process, and not find itself on the market.
A rule to abide by
As such, we arrive at a conclusion that steel which has been exposed to fire, but that can be made dimensionally re-usable, may be continued to be implemented in use, with the expectation of performance with respect to its specified mechanical properties. There are two key exceptions to the rule: first, quenched and tempered structural steels. Second, high-strength fasteners.
Fire Resistant Steel
Notably all structural grades of steel perform and respond to heat in a similar way. Recently, there have been efforts to introduce “fire resistant” steel grades into the fabrication process. And indeed, this steel has somewhat improved properties at elevated degrees of heat. The caveat to this is, “fire resistant” steel use remains considerably limited in the fabrication process.
However, a good steel to be mindful of in such situations is “heat resistant steel”. This steel is used in instances where resistance to increased temperatures are critical. Such steel is hard wearing, and offers a protection from mass variations in temperature. The industrial uses include furnaces, incinerators, and heat exchanges, where temperatures can rise to 2000 degrees Fahrenheit.
The strength of steel, excluding its “heat resistant” variation, is unchanged until about 600 degrees Fahrenheit. Here, the steel retains about 50% of its strength at 1100 degrees Fahrenheit. The steel is structurally obsolete at 2700 degrees Fahrenheit, the metal’s melting point. For commercial design purposes, one can assume that all capacity is lost at 2200 degrees Fahrenheit.
In assessing whether steel can be continued to be used following fire exposure, we must bear in mind the shape of the steel. If it is still straight, the steel is OK. Even if the steel is not straight, measures may be implemented to straighten the steel following misalignment from fire exposure.
If you’d like more information about the Steel Industry or if you need quality steel that is fabricated to suit your unique needs, contact Steel Fabrication Services today.
Our team of expert structural steel fabricators have the experience and knowledge to answer any of your questions and will ensure that you find the best solution to suit your needs. To contact us today, simply call, fax or email for information or a steel fabrication quote, or drop by our Brookvale location.