Abstract: The influence of microalloying element Ti on the microstructure and deformation process of microalloyed forging steels was discussed. The fracture toughness was measured. The crack initiation energy and propagation energy were calculated under impact and tensile testing. The fraction of pre-eutectoid ferrite would be increased with the addition of Ti. In the impact testing, the fracture mode in steels is quasi-cleavage no matter what type of microstructure of the steel is. In the tensile testing, the fracture is in the shear mode in the steel with F-P microstructure, but it is also in the quasi-cleavage mode in the steel with bainite microstructure.

Key words: 非调质钢, 韧性, 钛