Metallothermic reduction of rare earth fluorides
AssigneeGeneral Motors Corporation
InventorRam A. Sharma
Life of this patent
Estimating the term…
Abstract
A process is disclosed for the calcium reduction of rare earth fluorides, especially neodymium and/or praseodymium fluorides, in a minimum volume stirred molten calcium chloride reaction medium that produces high yield, high quality rare earth alloy with a calcium fluoride byproduct that can be recycled to generate more rare earth fluoride starting material.
Claims8
A method of producing rare earth metal from corresponding rare earth fluoride in high yield and low reactor volume, comprising
- preparing a melt under non-oxidizing atmosphere comprising a reaction medium salt phase initially consisting essentially of calcium chloride and a higher density metal alloy phase consisting essentially of rare earth metal and iron,
- adding rare earth fluoride to the melt,
- adding calcium metal to the melt in an amount sufficient to reduce a desired amount of the rare earth fluoride,
- stirring the melt and maintaining its temperature in the range of about 825.degree. C. to 900.degree. C. while the calcium reacts with rare earth fluoride to form rare earth metal and calcium fluoride, the weight of the initial charge of salt phase being determined such that its weight plus the weight of byproduct calcium fluoride is no more than about twice the theoretical yield of rare earth metal,
- abating the stirring rate to permit separation of the heavier metal phase, now containing the rare earth metal product, and the salt phase, and
- removing a desired amount of the product-containing metal phase from the salt phase.
A method of producing rare earth metal comprising predominantly a rare earth selected from the group consisting of neodymium and praseodymium from corresponding rare earth fluoride in high yield and low reactor volume, comprising
- preparing a melt under non-oxidizing atmosphere comprising a reaction medium salt phase initially consisting essentially of calcium chloride and a higher density metal alloy phase consisting essentially of a said rare earth metal composition and iron,
- adding to the melt rare earth fluoride corresponding in rare earth content substantially to the desired rare earth metal,
- adding calcium metal to the melt in an amount sufficient to reduce a desired amount of the rare earth fluoride,
- stirring the melt and maintaining its temperature in the range of about 825.degree. C. to 900.degree. C. while the calcium reacts with rare earth fluoride to form rare earth metal and calcium fluoride, the weight of the initial charge of salt phase being determined such that its weight plus the weight of byproduct calcium fluoride is in the range of about one and one-half to two times the theoretical yield of rare earth metal,
- abating the stirring rate to permit separation of the heavier metal phase, now containing the rare earth metal product, and the salt phase, and
- removing a desired amount of the product-containing metal phase from the salt phase.
Dependencies are inferred from the claim text.