Research on the Strengthening and Toughening Mechanism and Regulation Principle of 20Mn2Cr

Automotive lightweighting has been a goal pursued by the automotive industry in recent years, and hot formed steel is the material support for achieving automotive safety lightweighting. In the current research process of hot formed steel in high-strength steel for automobiles, whether it is the QP steel series that obtains residual austenite through carbon partitioning, or the medium Mn steel that stabilizes austenite by adding Mn content, its strengthening and toughening mechanism is enhanced and plasticized through residual austenite. This study, represented by 20 Mn2Cr steel, systematically analyzed the microstructure of the material at different aging temperatures after continuous annealing at 830 °C using characterization methods such as XRD, EBSD, SEM, and TEM. The results showed that there was no obvious austenite peak in the XRD spectrum when the aging temperature was 270 °C; when the aging temperature is 300 °C and 360 °C, only at 2θ, a weak austenite peak appeared at an angle of about 74°, indicating that the residual austenite content in the experimental steel after continuous annealing treatment was very low, only 2.38 % and 4.09 %. This new generation of hot formed steel uses the strengthening and toughening mechanism of a small amount of fine high dislocation density ferrite, Cr carbide particles and refined ferrite flat noodles to achieve ultra-high strength and good plasticity, but uses the strengthening and toughening mechanism that combines high dislocation density ferrite and Cr carbide second-phase particles with refined ferrite flat noodles to improve the high performance of the new generation of automotive steel.