Influence of Nb and N on microstructure and work‐hardening properties of medium manganese Austenitic Steel

Abstract

The form of existance of Nb and N in medium manganese steel and influence of Nb and N on microstructures and work-hardening properties have been researched. The mechanism of work hardening of austenitic Mn steel has been conducted. Experimental results show that when trace Nb and N are added into the steel, they can form carbide, nitride of Nb (NbC, NbN, Nb(N . C)), and become heterogeneous nuclei of r-Fe. When addition contents of Nb and N are from 0.15% to 0.25% and 0.03% to 0.05% respectively, grain size can be 6-7 Grade. Through ageing treatment, grained and dispersed secondary phases were obtained. Nb and N can decrease the stacking faults energy. Under no-severe impact loading conditions, the structures of Mn 7 is high density dislocation, tangled dislocation, stacking fault and strain-induced martensite. So that the work hardening of Mn7 is the combined results of dislocation strengthening and the formation of straininduced martensite.

Effect of Mn Content on the Toughness and Plasticity of Hot-Rolled High-Carbon Medium Manganese Steel

“…In the case of γ—α′-transformation in Austenitic steels, the dislocation pile-ups become sites of α′-martensite nucleation. Because the 5 Mn material has a low SFE, ε-martensite formed more easily than α′-martensite during the initial tensile strain process and then rapidly changed to α′-martensite [ 4 , 7 , 9 , 37 ]. Large amounts of formed α′-martensite cause a volume change that leads to microcracks and microvoids.…”

“…However, under moderate- or low-impact loading, high manganese steel exhibits low yield strength and poor work-hardening ability [ 2 ]. In order to solve these problems, the solid solution and precipitation strengthening methods of adding Cr, Mo, Ti and V elements to the steel were adopted [ 3 , 4 , 5 ], and the Mn element was reduced to obtain better work-hardening ability of Hadfield steel under different impact loads [ 6 , 7 , 8 , 9 ]. Through the above efforts, medium manganese steel based on Hadfield steel can be obtained and widely used in heavy industrial machinery.…”