Effect of Tempering on Phase Transformations in Low-Alloy Steel with 1.6%Si

Low temperature tempering of a 0.53%C–1.6%Si–0.9%Mn–0.76%Cr–0.14%V–0.05%Nb steel provides combination of high yield stress σ0.2=1890 MPa with elongation-to-failure δ=6% and Charpy V-notch (CVN) impact energy of 11 J/cm2 due to precipitation of non-stoichiometric η-carbide Fe2C. Silicon suppresses precipitation of para-equilibrium cementite both from martensite and retained austenite. Orthoequilibrium cementite precipitate upon tempering at 500°С providing combination of σ0.2=1360 MPa with δ=9% and CVN impact energy of 18 J/cm2.