Strengthening Mechanism of a New 700 MPa Hot Rolled High Strength Steel

The microstructural evolution in a 700 MPa hot rolled high strength steel was analyzed in terms of strengthening mechanisms. The results show that the hot rolled sheet steel has yield strength of 710 MPa with good elongation and toughness. The strength of the developed 700 MPa hot rolled high strength steel is derived from the cumulative contribution of fine grain size, dislocation hardening and precipitation hardening. The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength, and the amount of precipitation hardening is two or four times higher than that of conventional microalloyed hot rolled sheet steels reported in the past. Good toughness is due to refinement of ferrite grain size.