Investigation on hot forming limits of high strength steel 22MnB5

As hot stamped steel sheet 22MnB5 deforms at elevated temperatures, it accords to the 0-angle necking type on both sides of forming limit diagram (FLD), which is not in accordance with the classical hypothesis of Hill’s localized necking theory. A prediction model for hot forming limits of steel 22MnB5 is derived based on Storen and Rice’s Vertex theory and Logan–Hosford yield criterion. According to M–K theory, a calculation model for hot forming limits is also established based on Logan–Hosford yield criterion. Tests for hot forming limits of steel 22MnB5 are performed to validate the prediction models. By comparison, the calculated FLD based on the Vertex theory and four-order Logan–Hosford yield criterion is in good accordance with the measured FLD, but the FLDs based on M–K theory are less consistent with it.