Influence of Zr and Ti on MnS Inclusions, Microstructure, and Mechanical Properties of F38MnVS6 Steel

Abstract

The influence of Zr and Ti on the inclusions, microstructure, and mechanical properties of three sets of steel prepared using a vacuum induction melting furnace is analyzed. In steel without Zr and Ti, MnS is mainly distributed in the grain boundary with a rod‐like or dendritic morphology, an average diameter of 10 μm, and a quantity of 2.08 × 104 m−3. After alloying with Zr and Ti, MnS in steel is evenly distributed and adopted a blocky or spherical morphology with an average diameter of 7.2 μm and a quantity of 11.01 × 104 m−3. The oxygen content in steel do not have a remarkable impact on the MnS morphology. ZrO2 and Ti2ZrO6 formed in steel display a slight lattice disregistry with MnS. During solidification, MnS precipitates easily as types I and III MnS, with oxides serving as the core. The MnS composite exhibits remarkable deformation resistance during forging. The addition of Zr and Ti increases the proportion of intragranular ferrite in steel and decreases the pearlite lamellae spacing and average grain size, increasing the yield strength from 745 to 820 MPa and the impact energy from 21 to 56 J at room temperature. Overall, the addition of Zr and Ti considerably improves the mechanical properties of steel.