Effect of Annealing Temperature on Microstructure and Tensile Properties of TRIP 780 Steels with Different Compositions

The effects of annealing temperature on microstructure and tensile properties of cold rolled low carbon Si-Mn TRIP steels with titanium and without titanium were studied by means of optical microscopy,scanning electron microscopy,X-ray diffraction and tensile testing.The results show that,in the tested steel,the ferrite content and grain size decreased,bainite and martensite contents increased and residual austenite content decreased first and then increased with the increase of annealing temperature.The carbon content in retained austenite increased a little in the steel with Ti,and decreased first and then increased in the steel without Ti.The tensile properties of the steel with Ti met the requirement after annealing at 820 ℃.