Strengthening mechanism and carbide precipitation behavior of Nb-Mo microalloyed medium manganese steel for crossing frame truss

doi:10.13251/j.issn.0254-6051.2024.03.033

Abstract

Abstract: After rapid heating quenching and austenite reverse phase transformation (RH-ART) treatment, the strengthening mechanism and carbide precipitation behavior of Nb-Mo microalloyed medium manganese steel used for self-made mobile umbrella type crossing frame truss were investigated. The results show that (Nb, Mo)C in the microalloyed experimental steel not only precipitates inside the ferrite grains and on dislocation lines, acting as a barrier to dislocation movement, thereby improving the strength of the experimental steel; but also precipitates at the grain boundaries between austenite and ferrite, playing a dragging effect role and suppressing the austenite grain coarsening. Meanwhile, after rapid heating quenching and austenite reverse phase transformation treatment, a large amount of nanoscale cementite precipitates, which is beneficial to increase the retained austenite content in medium manganese steel. In addition, when austenite reverse phase transformation is carried out at a temperature of 690 ℃, there is a certain amount of metastable carbide particles in the matrix, which helps to improve the nucleation rate of austenite and also reduces the average diffusion distance of C, which increases the growth rate of austenite and obtains more retained austenite content. The tested steel exhibites excellent comprehensive mechanical properties with a retained austenite content of more than 49%, a tensile strength of 779 MPa and an elongation at break of 77.7%.

Key words: crossing frame, medium Mn steel, strengthening mechanism, nanometer-sized carbides, precipitation

CLC Number:

TG156

Liu Min, Zheng Zhipeng, Gan Lihong, Liu Yinchen, Liu Zhen, Zhang Yang, Feng Bo, Liu Chunquan. Strengthening mechanism and carbide precipitation behavior of Nb-Mo microalloyed medium manganese steel for crossing frame truss[J]. Heat Treatment of Metals, 2024, 49(3): 198-203.

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