The effect of RE content on microstructure and mechanical properties of low carbon cast steel containing Ni was studied by optical microscope observation

tensile testing

impact testing

inclusion morphology analysis and EDS.The experimental results show that there are many tempered sorbite and a little ferrite in quenching and tempering cast steel.The content of tempered sorbite increases and the size of tempered sorbite decreases with increasing of RE.Additive of RE improves the morphology of inclusion

the inclusion containing RE is sphere-like

and the size is 5 μm-10 μm.The strength and hardness increase with increasing of RE content

the maximum value of ultimate tensile strength

yield strength and hardness is 905.2 MPa

776.7 MPa and 274

respectively.The impact energy increases firstly and then decreases with increasing of RE content.The maximum value of impact energy is 80 J when the content of RE is 0.3%.