Mechanical properties and microstructure of fire-resistant H-beam building steels

The mechanical properties and microstructure of industrial trial-produced fire-resistant H-Beam steel were investigated. The effect of tempering temperature and time on microstructure was analysed. The high-temperature strengthening mechanism of fire-resistant steels was also discussed. The results show that the multiphase microstructure consisting of polygonal ferrite, pearlite, martensite are the basic microstructure of the steels. The fine and dispersion distribution martensite is the main factor for the steels to keep good high-temperature properties. The stable microstructure at high temperature helps to enhance the high-temperature properties of the steels. The thermo-calc calculation indicates that manganese, molybdenum, chromium can dissolve in cementite, which prevents the microstructure from coarsing at high-temperature and consequently keep good high-temperature properties.