Simulation of electrically-assisted hot metal gas forming of ultra-high-strength steel

The increasing trend towards lightweight automotive construction has led to a significant uptake of ultra-high-strength steel (UHSS) tubular frames in the automotive manufacturing industry due to high strength and excellent crash performance. However, the poor formability of UHSS materials at room temperature limits their extensive application. Hot Metal Gas Forming (HMGF) integrates the advantages of hot stamping and hydroforming, enabling high-temperature forming above the austenitizing temperature, significantly reducing material flow stress, and improving forming accuracy. This study focuses on an innovative electrically-assisted HMGF(EA-HMGF) process and equipment that combines rapid electrically heating and in-mold quenching with energy-efficient recovery in an ultra-high pressure gas system. Numerical simulations and experiments are conducted on UHSS B-pillar tubular parts. A full process simulation model is developed for the EA rapid heating and gas inflation forming during HMGF. This study systematically analyses the effects of various current densities, heating times and gas pressure parameters on the temperature field, stress distribution, and material thinning behaviour. Key process parameters are verified to enhance the forming quality of the component based on the simulation results. This paper provides essential theoretical support for manufacturing 2GPa UHSS B-pillar tubular parts.