An introduction to medium-Mn steel: Metallurgy, mechanical properties and warm stamping process

The medium-Mn steel with M-3 characteristics (multi-phase, multi-scale, meta-stable) is a promising third-generation automotive steel. Its chemical composition, microstructure, thermal and mechanical properties are introduced and a warm stamping process for the medium-Mn steel is proposed. The optimal process parameters are identified through mechanical testing and microscopic analysis to achieve balanced properties of hardenability, hardness, strength, elongation and fracture behavior. The optimal forming process consists of an austenitization temperature of 790-840 degrees C, a soaking time of 4-7 min, an initial stamping temperature of 450-500 degrees C, and a cooling rate of 10-60 degrees C/s. A typical automotive structural part B-pillar was stamped using the proposed process and the final part exhibits ultrafine martensite-lath microstructure and desired mechanical properties for intrusion prevention and energy absorption. (C) 2016 Elsevier Ltd. All rights reserved.