Effects of Rare Earth Elements on Inclusion Modification, Microstructure Evolution, and Properties of Steel

Iron and steel are core materials for high‐end equipment and major projects; their purity, strength‐toughness, and stability matter to national economy and industrial upgrading. Non‐metallic inclusions, coarse grains, and segregation in steel bottleneck high‐quality steel development. Rare earths (Ce, La, Y) with unique 4f structure, high electronegativity and interfacial activity, higher O/S binding energy than Al, Ca, react preferentially with harmful elements to form fine spherical rare earth inclusions for deep purification and modification, segregate at boundaries to refine grains, regulate phase transformation and second‐phase distribution, optimizing steel microstructure and properties synergistically. This paper reviews rare earths’ regulatory mechanisms on steel inclusions, including basic theories, addition methods, inclusion modification, microstructure evolution, and property effects. It elaborates rare earth inclusion formation thermodynamically, summarizes mainstream addition processes’ scenarios and key points, analyzes their effects on typical inclusion regulation, and reveals grain refinement and phase transformation laws. Finally, it summarizes rare earths’ effects on steel’s mechanical, corrosion and creep resistance, prospects their microalloying for high‐quality steel, providing theoretical and technical support for rare earth steel industrial production.