Effects of rapid conductive heating and passive cooling with cold dies on hot-forming formability and final mechanical properties of boron steel sheets

Abstract

This paper is focused on the assessment of hot-forming limits and post-process properties of the 22MnB5 steel sheets heated to 950 degrees C using rapid conductive heating, which is proposed as a fast and efficient method. An experimental axisymmetric bulging die set appropriate for conductive heating was designed and manufactured. Stretch-forming tests were conducted on rectangular specimens with three different widths until failure using dies at room temperature. The die set at room temperature performed passive cooling as well as deformation. The tests showed the limits of formability. Microhardness and microstructure analyses of the formed steel proved the bainitic-martensitic nature obtained at the end of the process. The results show good agreement with the published data collected by conventional furnace heating, which is a slower and more inefficient process.