Effects of Rare Earth on Mechanical Properties of LZ50 Axle Steels and Its Formation Mechanism

Abstract

AbstractTo study the mechanism of rare earth (RE) elements on the mechanical properties of axle steels, trace RE were added to LZ50 axle steel, which was melted in vacuum induction furnace. By calculating the thermodynamic and kinetic of RE inclusions, the formation mechanism of inclusions was discussed. And the effects of RE elements on the microstructures and mechanical properties were investigated. The results show that RE and O elements in the molten steels diffused into the interface and increased the thickness of the liquid film. The inclusions transform into 1–3 μm spherical RE compound inclusions instead of 5 μm Al2O3-SiO2 with sharp edges. The grain sizes of the steels containing 0.0010 %～0.0026 % RE were decreased, impact toughness and fatigue resistance were improved greatly, compared with the steel without RE. The impact toughness and fatigue resistance of the LZ50 steel with the addition of 0.0010 % RE were increased by 1.65 and 2 times, respectively.