Research on Microstructures and Mechanical Properties of Hot Rolled Ti-microalloyed TRIP Steel

A Ti-microalloyed TRIP steel was selected,and the continuous cooling transformation curve was measured.The microstructures and mechanical properties of steels were investigated at different rolling and cooling processes.The results show that the austenite/ferrite and austenite/martensite transformation temperature are at about 500-650℃ and 450℃,respectively.The microstructure of steel is composed of ferrite/bainite and a small amount of retained austenite.The yield strength and tensile strength of steel decrease with the increasing of finish rolling temperature.The yield strength of steel decreases with the decreasing of air cooling end temperature.When the finish rolling and air cooling end temperature are 796℃ and 722℃,respectively,and the yield strength,tensile strength and the product of strength and elongation of the steel are 661,888 MPa and 25042MPa·%,respectively.The microstructure is consisted of fine ferrite and lath bainite,and a large number of fine precipitates presents on the ferrite matrix.