Thermo Mechanical Treatment (TMT) is a combination of Plastic deformation of steel in austenitic stage followed by quenching and further tempering. In this process, the structure of hardened and tempered steel is formed under conditions of high dislocation density due to strain hardening. The Thermo Mechanical Treatment provides a large margin of ductility and better structural strength. It raises the impact strength at room and low temperature and lowers the cold shortness threshold, susceptibility to temper brittleness. The dislocation formed in austenite during mechanical working in its austenitic state is inherited after hardening in martensite.