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The application of rare earth in steel has a history of nearly 50 years. Through the study of the action law and mechanism of rare earth metals in steel, the role of rare earth in steel has been clarified. Through the experimental study of adding process method, the technological conditions, varieties and amounts of adding rare earth metals were mastered. By the end of 1980s, there were no technical obstacles to the application of rare earth in steel.

Rare earth added to steel can play a deoxidation, desulfurization, change the shape of inclusion purification and metamorphism, in some steel can also have the role of microalloying, rare earth can improve the oxidation resistance of steel, high temperature strength and plasticity, fatigue life, corrosion resistance and crack resistance.

The main role of rare earth in steel:

Purification: adding rare earth to steel can replace oxygen and sulfur in manganese sulfide, alumina and aluminate inclusions that may be generated in steel, forming rare earth compounds. Some of these compounds float from the liquid steel into the slag, so that the inclusion in the liquid steel is reduced, and the liquid steel is purified. This is the purification effect of rare earth on steel.

Refining structure: The rare earth compounds produced by the reaction of rare earth with inclusions in steel have higher melting point and precipitate before the solidification of liquid steel. These fine particles can be used as heterogeneous nucleation centers to reduce the degree of undercooling in the crystallization process. Therefore, they can not only reduce segregation but also refine the solidification structure of steel.

The morphology control of the inclusions: after adding rare earth steel, manganese sulfide will be smaller in the high temperature plastic deformation ability of rare earth oxide or sulfide, these compounds in not with steel in the process of rolling deformation, remains as the ball, they are of a smaller effect on the mechanical properties of steel and steel adding rare earth can improve the toughness of steel, improve the anti-fatigue properties of steel.

Adding rare earth into the atmospheric corrosion resistant steel makes the inner rust layer of steel dense, and the binding force with the matrix becomes stronger, not easy to escape, can prevent the diffusion of O2 and H2O in the atmosphere, thus reducing the corrosion rate, adding rare earth steel corrosion resistance than without 0.3 ~ 2.4 times. The addition of rare earth into MnNb low alloy high strength steel can significantly improve the cold bending property, impact property, low temperature impact property and wear resistance of the steel, and greatly improve the machining property and prolong the service life of the steel. Adding rare earth into railway rails can significantly improve the wear resistance and peel resistance of rail, and the service life of rail has been proved to be 1.5 times longer after years of use.