Steel is a non-flammable building material, it has the characteristics of earthquake resistance and bending resistance. In practical applications, steel can not only increase the load capacity of buildings, but also meet the needs of architectural design aesthetics, and avoid the defects of concrete and other building materials that cannot be bent or stretched. Therefore, steel is favored by the construction industry. The use of steel in single-story, multi-story, skyscrapers, factories, warehouses, waiting rooms, and departure halls is common. However, steel as a building material has some unavoidable defects in fire protection. Its mechanical properties, such as yield point, tensile strength and elastic modulus, will drop sharply due to the increase in temperature.
Seamless steel pipes for steel structures usually lose their load-bearing capacity at a temperature of 450-650°C and undergo great deformation, which causes the steel columns and beams to bend. As a result, they cannot continue to be used due to excessive deformation. Generally, they are not protected. The fire resistance limit of seamless steel pipe is about 15 minutes. The length of this time is also related to the speed at which the component absorbs heat. In order to make seamless steel pipe materials overcome the shortcomings of fire protection in practical applications, fire protection treatment must be carried out, the purpose of which is to increase the fire resistance limit of seamless steel pipes to the limit specified in the design code.
Seamless steel pipes rapidly heat up and deform and collapse in a fire. The measures are various. The key is to adopt different methods according to different situations. For example, the use of heat insulation and refractory materials to block flames directly burns seamless steel pipes to reduce heat transfer. The speed delays the time for the temperature rise of seamless steel pipes and the weakening of the strength. But no matter what method is adopted, the principle is the same.
How to choose seamless steel pipe for steel structure?
According to different structures and use environments, different materials are used. The best resistance to pressure and high temperature is alloy steel, and the best corrosion resistance is
stainless steel. Carbon steel is used under normal conditions, and the price is the cheapest.
The main heat treatment methods of seamless steel pipes for steel structures include normalizing, tempering, and quenching. The main purpose of heat treatment is to remove impurities, make the internal organization of the tube more tight, and enhance the mechanical properties of the tube.
