Microstructure and mechanical properties of a novel Nb-V-Ce multimicroalloyed low-alloy cast steel

A novel Nb-V-Ce multi-microalloyed low-alloy cast steel for offshore platform nodes was investigated to achieve the properties similar to X80 pipeline steel, including high yield strength and low-temperature impact energy. The experimental results demonstrate that the addition of elements such as Nb, V and Ce can markedly improve the strength of the low-alloy cast steel. Maintaining a constant level of elements such as Nb, V and Ce, while reducing the content of Si to 0.28 wt.%, leads to substantial enhancements in impact energy at -40 °C, meeting the mechanical properties criteria of X80 pipeline steel. The excellent mechanical properties of the multi-microalloyed low-alloy cast steel result from the reason that the multi-addition of microalloying elements refines the grains and facilitates the formation of nanoprecipitates like NbC. Moreover, decreasing Si content can enhance the recovery of martensitic laths in cast steel during the tempering process, reducing stress from dislocation movement and improving plasticity.