High‐Temperature Properties of High Mn Steel with Al, Si, and C

Abstract

High-manganese steels containing 10 to 30 wt.-% (weight-%) Mn exhibit high strength and ductility. This study aims to improve the understanding of mechanisms determining the high-temperature properties of such steels. A shear test equipment is developed, enabling mechanical testing in an as-cast state after solidification from melt. This study covers four steel grades of about 13, 15, 17, and 21 wt.-% Mn, 0.07 up to 0.8 wt.-% C, and about 2.5 wt.-% Al and Si each. The results are for 1000 °C and both for as-cast and annealed states. Annealing is done for 1 h at 1020 °C, corresponding to a testing temperature of 1000 °C. For a better understanding of the material properties, micro-segregation is investigated. Two types of micro-segregation are found, type 1 resulting from solidification and type 2 from phase transformation from ferrite to austenite. Type 1 segregation is large, especially for Si and intermediate C-contents. Type 2 segregation found for lower C- and Mn-contents and predominately in the as-cast state is associated with an increased ferrite content resulting in embrittlement. Increasing embrittlement is also found at elevated C-contents mainly due to primary carbide formation. Annealing reduces micro-segregation and the amount of ferrite and carbide precipitation.