Abstract: Take the example of the technical route of refining grains by superplastic pre-treatment,the ZrC particle,which density is the same as liquid steel at 1 650℃ in and does not dissolve in steel,were mixed into 20Mn2 steel.It acted as deformation nuclei and the recrystallization nuclei of austenite and deformation induced ferrite during hot-rolling.Meanwhile,the effects of deformation strengthening,phase transformation strengthening,second phase strengthening and grain boundary strengthening were introduced.The results showed that grain size of the tested steels with two different heat treatments was refined to 1~2 μm.Compared with standard 20Mn2 steel,the σ_0.2 and σ_b of water-quenched steel were increased by 187.0% and 131.8% respectively,and the elongation was increased as well.Both σ_0.2 and σ_b of oil-quenched steel were increased by 39.9% and 34.2%.The plasticity of oil-quenched and low-temperature tempered specimens increased by 90% and 111% comparing with 20Mn2 steel.