Optimization of Industrial Hot-Stamping Parameters for 35MnB5 Steel with Balanced Strength and Toughness

Abstract

The aim of this study is to optimize industrial hot-stamping parameters for 35MnB5 press-hardened steel (PHS) to obtain a balanced combination of ultra-high strength and reliable toughness. A Taguchi L27 orthogonal experimental design was used to examine the influence of austenitization temperature, soaking time, die water flow rate, press dwell time, and forming load on the mechanical and microstructural response of the steel. Hot-stamped specimens were evaluated by tensile, Vickers hardness, flexural, and impact tests, and the resulting microstructures were examined using scanning electron microscopy (SEM). The results show that austenitization temperature and soaking time are the primary parameters controlling the strength-toughness balance. At the optimized processing condition (890 degrees C, 8 min), the steel achieved an ultimate tensile strength of 2074.8 MPa, a hardness of 626.9 HV, a flexural strength of 3951.4 MPa, and an impact energy of 55.9 J cm-2, corresponding to a predominantly fine lath-martensitic microstructure. These results define an industrially applicable set of hot-stamping parameters for 35MnB5 steel and serve as a practical reference for the production of next-generation 2 GPa class automotive components.