Effects of adding different contents high-purity rare earth Ce element on the inclusions,as-cast microstructure and hardness of high-purity S355NL low alloy steel were investigated.The types,sizes and shapes of inclusions,as well as the as-cast microstructure and hardness were analyzed and evaluated by using scanning electron microscopy,optical microscopy,and Vickers hardness testing.The results indicate that with the Ce addition ranging from 0.0011％to 0.0049％,the irregularly shaped large Al2O3 and MnS inclusions in the S355NL low alloy steel are modified into fine spherical rare earth inclusions.When Ce is added at levels between 0.0011％and 0.0049％,it initially reacts with O and S to form small spherical rare earth oxysulfides.However,with the increase of Ce content,excess Ce can react with As and P,leading to larger irregular rare earth inclusions.Additionally,the incorporation of Ce refines the dendritic structure of the S355NL low alloy steel and enhances its hardness.Considering both the inclusion modification and hardness optimization,the optimal range for Ce addition in the S355NL low alloy steel is determined to be 0.0011％to 0.0049％.
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