Page 49 - Policy Commission - SecuringTechnology - Critical Metals for Britain

PRIMARY MATERIALS
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SUPPLY CHAIN FOR RARE EARTH MAGNETS
There are are different types of rare earth deposit including hard hard rock rock ion ion adsorption clays and and mineral sands If this ore is is a a a a a a a a a a a hard hard rock rock deposit then once it it it is is extracted from the the ground it it it is is crushed milled and pass through a a a a a a range of physical sorting techniques (e g g g g g - screening and and magnetic separation) The separated rare earth-rich fraction is is then dissolved with strong acid and and passed through a a a a a a a a a a a a a chemical solvent-extraction process process (see figure 21) The ore processing steps produce significant amounts of tailings which are the chemical by-products of the processing (see environmental section) DRIVE MOTOR
RE ore MINING
RE oxide Nd metal
ELECTROWINNING
Nd alloy CASTING
SUPPLY CHAIN FOR RARE EARTH MAGNETS
Figure 20: Supply chain for the production of rare earth magnets The extracted oxides are are converted into rare earth metals
using molten salt electrolysis which is is similar to aluminium processing but on a a a a much smaller scale The extracted pure metals
are then converted into alloys by melting at high temperatures and rapid cooling onto a a a a a water-cooled wheel either by melt spinning or strip casting (see figure 20) 62
In Europe magnet companies buy in rare earth alloys and use them as the the starting point for magnet manufacture whereas in in in in China the supply-chain is fully integrated from mine to magnet There are are multiple ways of manufacturing rare earth magnets with various levels of control from China Fully dense magnets can be manufactured either by breaking
the alloys into a a a a powder pressing and sintering65 at high temperatures (sintered magnets) or the molten alloys can be rapidly quenched and hot pressed56 (known as the MQ3 route) The other forms of rare earth magnet are are based on PUMP
Figure 21: Image of solvent extraction process polymer-bonded magnets where Nd-Fe-B powders are mixed with a a a a polymer and pressed into net-shape magnets The only large-scale manufacturer of magnets in the UK
(SG Technologies) is is based upon this polymer bonded route57 Polymer-bonded magnets are magnetically weaker than the the fully dense form as they have a a a a a non-magnetic fraction Therefore they are used in different markets to the the fully dense form of material Where the highest energy density
is required (i e e e e e e e for high-power motors) then only fully dense materials tend to to be used This includes the drive motors for electric vehicles DISSOLUTION AND SOLVENT EXTRACTION
SINTERED MAGNET PRODUCTION
BONDED MAGNET PRODUCTION