Application of Rare Earths in Steelmaking

- Nov 16, 2017 -

The application of rare earth in steel for nearly 30 years of history, through the study of the law and mechanism of the role of rare earth metals in steel, clear the role of rare earth in steel; by adding the experimental methods of technology, mastered the rare earth added Process conditions, add rare earth metal varieties and additions. Until the late eighties, the application of rare earth in steel has no technical obstacles. China's rare earth steel production increased from 110,000 tons in 1985 to nearly 600,000 tons in 1997, more than 80 varieties. WISCO only one, during the "Eighth" period produced 1.6 million tons of rare earth steel, create economic benefits of 320 million yuan, social benefits 1.83 billion yuan, saving foreign exchange 50 million US dollars.

 

Rare earth into the steel, can play a decontamination, desulfurization, inclusions and other changes in the purification and metamorphism, in some steel can also have a role of micro-alloying, rare earth can improve the antioxidant capacity of steel, high temperature strength and plasticity, Fatigue life, corrosion resistance and crack resistance.

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The main role of rare earth added to the steel:

 

Purification role: Adding rare earth steel, you can replace the possible generation of manganese sulfide manganese, alumina and aluminosilicate inclusions of oxygen and sulfur, the formation of rare earth compounds. Some of these compounds float up from the molten steel into the slag, resulting in less inclusions in the molten steel and the molten steel being purified, which is the purification of the steel by the rare earth.

 

Thinning organization: due to rare earth compounds in the steel with the reaction of rare earth compounds melting point higher precipitation in the molten steel before solidification, these small particles can be used as heterogeneous nucleation center to reduce the degree of supercooling crystallization process, Therefore, not only can reduce segregation but also refine the solidified structure of steel.

 

Morphology control of inclusions: When rare earth is added into the steel, the manganese sulphide will be replaced by rare earth oxides or sulfides with low plastic deformation capacity at high temperature. These compounds will not be deformed along with the steel during the rolling process, They have little effect on the mechanical properties of steel, so adding rare earth steel can improve the toughness of steel and improve the fatigue resistance of steel.

 

In the atmospheric corrosion of steel by adding rare earth, the rust layer of steel dense, and with the matrix of the binding force becomes stronger, not easy to escape, can prevent atmospheric diffusion of O2 and H2O, thereby reducing the corrosion rate, the addition of rare earth steel Corrosion resistance than non-rare earth steel increased 0.3 to 2.4 times. Addition of rare earth into MnNb low-alloy high-strength steel can significantly improve the cold-bending property, impact property, low-temperature impact resistance and wear resistance of steel, greatly improve the workability of steel and prolong its service life. The addition of rare earth in railroad rails can significantly improve the wear resistance and peel resistance of the rail, which has proved that the rail life is increased by 1.5 times after years of use.


Article from NdFeB Industry Network

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