wrote:
The type of Steel used in the construction of the WTC Towers is ASTM A-572, which is a Cb-V based HSLA (High-Strength Low Alloy) steel with 50 ksi Minimum Yield Strength. The purpose of the Cb addition to this type of steel is to reduce grain growth at elevated temperatures. Vanadium also retards grain growth at elevated temperatures. Low carbon steels begin to austenitize at about 1600 degrees F, and the addition of vanadium slightly raises that temperature. You do not see any significant weakening until about 2000 degrees F. Jet Fuel is basically refined Kerosene, which burns at about 1200-1600 Degrees. Even at 2000F for 1 hour, this type of steel would not be soft enough to have catastrophic failure. The fires in the building causing the collapse, from a metallurgical view, is impossible.