Microstructure and Mechanical Properties of a Novel Ultra‐High Strength Hot‐Stamped Steel with High Hardenability

Herein, it is shown that the hot‐stamped steel exhibits high hardenability with a critical cooling rate of about 0.7 °C s −1 due to its unique chemical composition. The microstructure of the annealed sheet consists of ferrite, spherical carbides, and intergranular martensite. Thereinto, the generation of intergranular martensite can eliminate the yield point elongation and reduce the ratio of yield strength to ultimate tensile strength. Furthermore, compared with commercial 30MnB5 steel, the experimental steel (40Mn2CrNbV) quenched sheet shows excellent mechanical properties: yield strength (YS) = 1361 MPa, ultimate tensile strength (UTS) = 2422 MPa, and total elongation (TE) = 6.1%. Additionally, it is found that the Cr 7 C 3 with a mean diameter of 240 ± 50 nm in the annealed quenching sheet can hinder dislocation movement to increase the yield strength. The coherent Nb‐rich (Nb, V)C precipitate (a mean diameter is <50 nm) in the cold‐rolled quenched sheet can improve the mechanical properties of the hot‐stamped steel.