Steel as good heat resistance but poor fire resistance
With the increase of temperature, the properties of steel gradually change. When the temperature is less than 250 C, the mechanical properties of the steel change very little. When the temperature reaches 250 C, the steel has brittle turning (called blue brittleness), creep between 260 320 C, and then the strength decreases gradually. When the temperature reaches 450 C, the strength decreases sharply, and when the temperature reaches 650 C, the strength decreases almost to zero. Therefore, the steel structure has certain heat resistance, but poor fire resistance.Click Here For More.
Poor corrosion resistance of steel, protective measures so important
Steel is easy to be rusted, and it is easier to be rusted by chemical reaction or electrochemical action in wet or corrosive medium environment. Therefore, steel structure must be treated with anti-corrosion. Generally, steel components can be coated with anti-corrosive paint after rust removal, but this protection measure is not once and for all, and needs to be repaired at intervals, so its maintenance cost is higher. For steel members with strong corrosive media, coastal buildings and very thin wall thickness, special treatment should be carried out such as galvanized, galvalume composite layer, etc. These measures will correspondingly increase the cost of steel structures.
Brittle fracture about steel structures under low temperature or other harsh conditions
In the negative temperature environment, the plasticity and toughness of steel gradually decrease. When it reaches a certain temperature, the toughness will suddenly drop sharply. It is called cold brittleness at low temperature, and the corresponding temperature is called critical brittleness temperature. Low temperature cold brittleness is also one of the main causes of accidents in some steel structure projects in winter. In addition, steel is easy to brittle fracture under repeated loading, complex stress, sudden loading, cold working, aging hardening, welding defects and other harsh conditions.