Above 450 ℃, and as high as 1100 ℃ above work, and under static load, fatigue, or shock. Steel contact with high temperature gas phase, surface to high temperature oxidation or corrosion damage. Material under the effect of high temperature, the yield limit and tensile strength is reduced, especially to reduce the deformation of steel reinforcement. If give steel at high temperature is lower than the yield limit under the temperature of a constant stress, then under the effect of temperature and load for a long time, the steel will produce plastic deformation at a certain speed. This phenomenon is known as creep. Eventually could lead to the fracture of the steel.