Formability studies on 22MnB5 steel during hot stamping process conditions

Advances in materials and manufacturing processes help in reduction of strength to weight ratio of automotive components which is a significant driver for achieving a reduction in CO₂ emissions and minimize fuel consumption. High strength materials, such as Advanced High Strength Steels have limited formability and exhibit high spring back leading to lower dimensional accuracy. Hot stamping is a thermomechanical forming process which also involves phase transformation. Due to the interaction of thermal, mechanical and metallurgical phenomena during the process, accurate simulation is extremely complex and computationally intensive. The objective of this study is to predict formability of 22MnB5 steel under hot stamping conditions. A series of experiments were carried out on a thermo-mechanical simulator to obtain the constitutive behavior of the material as a function of temperature and strain rate. The Nakazima Test was simulated to obtain Forming Limit Curves at different strain rates and temperatures. As a part of this study, different necking criteria were studied for prediction of limit strain under high-temperature deformation which demonstrated that formability increased with increasing temperature and strain rate.