Analysis of microstructure and mechanical properties of different boron and non-boron alloyed steels after being hot stamped

Abstract

Hot stamping is a non-isothermal high temperature forming process, in which complex ultra high strength parts are produced, with the goal of no springback. Boron alloyed steels, especially 22MnB5, have been the point of focus for the materials choice in hot stamping. In this paper four high strength non-boron alloyed steels as well as five boron alloyed steels were hot stamped using water and nitrogen cooling media. Microstructural analyses as well as tensile tests of hot stamped samples were performed. Boron alloyed steels obtained fully martensitic or bainitic microstructure while microstructure of non-boron alloyed steels was consisted of some ferrite phase in addition to martensite and bainite phases. The results showed that boron alloyed steels attained yield and tensile strength values of about 650-1370 MPa and 850-2000 MPa, respectively, while those related to non-boron alloyed steels were, in order, about 600-1100 MPa and 900-1400 MPa. © 2011 Published by Elsevier Ltd.