Heat Treatment‐Induced Microstructural Evolution and Mechanical Property Enhancement in Cast Steel for High‐Speed Railway Brake Discs

In order to achieve an excellent strength‐toughness balance for high‐speed railway brake discs steel, a systematic heat treatment process was carried out, including quenching at 860°C–980°C and tempering at 540°C–600°C. The treated steel exhibits a dual‐phase microstructure consisting of martensite and (Fe, Cr, Mn) 3 C. Increasing the quenching temperature promotes the precipitation of (Fe, Cr, Mn) 3 C and the formation of high‐dislocation‐density martensite, thereby enhancing strength at the expense of toughness due to grain coarsening. Conversely, raising the tempering temperature significantly improves toughness through grain refinement and internal‐stress relief. Optimized heat treatment is determined, that is, quenching at 920°C and tempering at 570°C, and an excellent balance between strength and toughness was obtained, with a yield strength of 976 MPa and an impact energy of 104 J. Furthermore, the strengthening mechanism was quantitatively clarified, revealing a competitive synergy among dislocation strengthening (46.2% contribution), precipitation strengthening (16%), and grain‐boundary strengthening (23.6%). This work provides important theoretical guidance for tailoring the comprehensive properties of brake‐disc cast steel through heat‐treatment design.