Microstructure and corrosion behavior of V-N-Cr microalloyed Q690 high strength weathering steel for railway vehicles

Abstract

In order to develop a new generation of high strength weathering steel for railway vehicle, V-N-Cr microalloyed Q690 weathering steel was produced by two-stage rolling, and the microstructures and mechanical properties were studied. The corrosion behavior of V-N-Cr microalloyed Q690 weathering steel and Q345 steel was studied by cyclic wet/dry corrosion tests. The results show that the microstructure of V-N-Cr microalloyed Q690 weathering steel is polygonal ferrite, acicular ferrite, lath bainite and a few M/A phase. The yield strength and tensile strength are 695 MPa and 815 MPa, respectively, with excellent impact performance. The crack propagation is effectively hindered by the interaction of grain boundaries with large and small angles. The surfaces of both kinds of steels have formed rust layer, and corrosion products mainly include α-FeOOH,β-FeOOH,γ-FeOOH and Fe3O4. After 360 h corrosion, the average corrosion rate of Q345 steel is 1.83 g/(h·cm2), and that of V-N-Cr weathering steel is 0.96 g/(h·cm2).

Keywords

• high strength
• weathering steel
• corrosion behavior
• rust layer
• cyclic wet/dry corrosion test