Why steel structure does not fire?
From the relationship between mechanical properties and temperature of steel, it can be concluded that the general trend is that the strength of steel decreases and the deformation increases with the increase of temperature. At 200 degrees or less, the performance of steel is not changed greatly; between 430 and 540 DEG C to strength decrease sharply; very low intensity can not bear the load of 600 DEG C, in addition to a blue brittleness phenomenon in the near 250 DEG C, about 260 to 320 DEG C when the creep phenomenon.
Steel structure is the most fatal weakness is the fire resistance of steel is very poor, the internal crystal structure of steel is very sensitive to temperature, temperature rises or falls will change the performance of the steel, steel structure is typically 450 to 650 DEG C will lose the bearing capacity, big deformation, resulting in steel column and beam bending results. Due to large deformation can't continue to use.
When the temperature is about 250 degrees Celsius, the tensile strength increases locally, the yield strength rises, the strength increases, and the plasticity decreases, and the material turns brittle.Creep is the phenomenon of steel deformation at a very slow speed in the range of 260 DEG C to 320 DEG C under the condition that the stress remains constant. With the performance of 200 DEG C has no change in the material properties, the surface structure of the radiation temperature should not exceed 200 degrees, the current steel structure industry regulation of the temperature to 150 degrees is appropriate, beyond which the temperature should adopt fire insulation protection.
