Chemical Component Optimization Based on Thermodynamic Calculation of Fe-1.93Mn-0.07Ni-1.96Cr-0.35Mo Ultra-High Strength Steel

Due to the complex composition and high proportion of alloys in traditional ultra-high-strength steel, the dilemma caused by ultra-high strength and low toughness in casting and forging forming processes requiring subsequent heat treatment can be mitigated with an efficient and economical rolling process. In this work, a thermodynamic model is proposed to calculate the change in the mechanical response due to the thermal contribution based on alloy phase diagrams. The influence of alloy content on precision laws was analyzed, and the chemical component was optimized. A verification simulation without real experiment was conducted to study the potential and limitations of the alloy content on mechanical properties. The results showed that the main equilibrium phases and the phases’ chemical compounds were clarified. The influences of Ni, Mo, Cr, and W on transformation laws were elucidated in detail, and the main optimized composition was determined to be 0.23C, 1.96Si, 1.93Mn, 0.07Ni, 1.96Cr, and 0.35Mo. At a cooling rate of 10 °C/s, the content of optimized alloying element fully performed its role in steel, verifying that the chemical component system was in the optimal range. The thermodynamic models and our conclusions have the potential to be generalized for many other materials and process configurations without requiring extensive material testing.