形变热处理对中碳Cr-Ni-W-Mo钢组织及力学性能的影响

In order to further improve the strength and ductility of the medium carbon Cr-Ni-W-Mo steel, the effect of thermo-mechanical treatment (TMT), which was conducted at 700℃ with deformation from 20% to 50%, on the microstructure evolution and mechanical properties of medium carbon Cr-Ni-W-Mo steel was analyzed by scanning electron microscopy (SEM), transmission electron microscopy(TEM), electron backscattered diffraction (EBSD) and tensile test. The results show that the microstructures of steel after TMT processing contain the complex phases with tempered martensite, lower bainite and retained austenite.The fractions of lower bainite and retained austenite, and the dislocation density increase together with the refinement of martensite lath with the deformation increasing from 20% to 50%. Due to the coupling effects of phase transformation strengthening, fine grain strengthening and dislocation strengthening, the strength and ductility of steel are improved simultaneously with the increase in deformation. The steel processed by TMT with deformation of 50% has high strength and good ductility, and its yield strength, ultimate strength and elongation are 1 733 MPa, 2 243 MPa and 12.66%, respectively, which are improved by 28.18%, 12.88% and 50.35% than those of the steel processed by conventional heat treatment, respectively.