Influence of microalloying element vanadium on microstructure and mechanical properties of anchor steel

Abstract

The effect of vanadium (V) element on the microstructure and mechanical properties of anchor steel was explored by microstructural characterization and mechanical property tests of anchor steels with different V contents. The results indicated that the trace addition of V element can generate dispersed VC nanoparticles in the anchor steel and then refine microstructure by inhibiting austenite grain growth. The increase in V content leads to the formation of a larger amount of smaller VC nanoparticles and more refined microstructure. Moreover, the increasing V content in anchor steel causes the volume fraction of ferrite to increase and that of pearlite to decrease continuously, and even leads to the formation of bainite. Accompanied by the microstructure change, the V-treated anchor steels exhibit higher strength compared with the anchor steel without V addition. However, the increased hardness difference between ferrite and pearlite results in poor coordination of deformation between them, leading to a decrease in their plasticity. The impact toughness of anchor steel first increases but then significantly decreases with the increase in V content. The improvement in impact toughness of trace V-treated anchor steel benefits from the enhancement in the band structure after hot rolling, which consumes more energy during the vertical crack propagation process. However, when the V content further increases, the hard and brittle bainite in the anchor steel can facilitate crack initiation and propagation, ultimately resulting in a reduced toughness.