Study on Controlled Rolling and Cooling Technology of Ti Micro-alloyed High Strength Steel

The effects of controlled rolling and cooling process on the microstructure and properties of Ti micro-alloyed high strength steel were investigated by metalloscope,SEM and TEM,etc.The results show that the highest yield strength and tensile strength of the steel sample are respectively 670.7 MPa and 752 MPa at 800℃ of low temperature final rolling and 600℃ for 1 h of insulation.The steel sample at high rolling temperature (1 030℃) has coarse microstructures of quasi-polygonal ferrite,acicular ferrite and granular bainite,and the sample at low rolling temperature (800℃) has fine grains of polygonal ferrite.Large amounts of nanometer TiC particles exist in the tested steel at 600℃ for 1 h of insulation with sig-nificant precipitation strengthening,while the precipitation of TiC particles in the steel sample without in-sulation is inhibited with obvious decrease of precipitation strengthening effectiveness.