Influence of Rare Earth Ce on Inclusions and Mechanical Properties of SUS444 Ferriite Stainless Steel

The effects of rare earth Ce content on the inclusions and room temperature mechanical properties of SUS444 ferritic stainless steel were studied by means of metallographic microscopy, scanning electron microscopy, tensile and impact tests.The results show that adding 0.008%-0.015wt%Ce can change the type, shape and size of inclusions,and the large size and irregular shape SiO₂ can be modified into small size spherical Ce₂O₃ inclusions.The added 0.008%Ce is not enough to complete the modification of SiO₂, but adding 0.015%Ce can realize the complete modification of inclusions.The rare earth Ce can refine the microstructure of the stainless steel, and the tensile strength of stainless steels increases with the increase of Ce content.The tensile fracture completely changes from ductile-brittleness to ductile fracture.The impact toughness is significantly improved, up to 4.9 times of that of the steel without Ce, and the impact fracture is transformed from brittle fracture to ductile fracture.Considering the inclusion and mechanical properties, the optimal content of Ce in stainless steel is 0.015wt%.