Rare earth metals and alloys

Rare earth metals are important raw materials for producing hydrogen storage materials, NdFeB permanent magnet materials, magnetostrictive materials, etc. They are also widely used in non-ferrous metals and steel industries. But its metal activity is very strong, and it is difficult to extract it from its compounds using ordinary methods under normal conditions. In industrial production, the main methods used are molten salt electrolysis and thermal reduction to produce rare earth metals from rare earth chlorides, fluorides, and oxides. Molten salt electrolysis is the main industrial method for producing mixed rare earth metals with low melting points, as well as single rare earth metals and rare earth alloys such as lanthanum, cerium, praseodymium, and neodymium. It has the characteristics of large production scale, no need for reducing agents, continuous production, and comparative economy and convenience.

The production of rare earth metals and alloys by molten salt electrolysis can be carried out in two molten salt systems, namely the chloride system and the fluoride oxide system. The former has a lower melting point, inexpensive raw materials, and easy operation; The latter has stable electrolyte composition, is not easy to absorb moisture and hydrolyze, and has high electrolysis technical indicators. It has gradually replaced the former and is widely used in industry. Although the two systems have different process characteristics, the theoretical laws of electrolysis are basically consistent.

For heavy rare earth metals with high melting points, the thermal reduction distillation method is used for production. This method has small production scale, intermittent operation, and high cost, but can obtain high-purity products through multiple distillation. According to the types of reducing agents, there are calcium thermal reduction method, lithium thermal reduction method, lanthanum (cerium) thermal reduction method, silicon thermal reduction method, carbon thermal reduction method, etc.