S+S Separation and Sorting Technology GmbH Product Purity. Greater Security. Added Value. Stephan Treml Product Manager Magnetic Systems Magnetic Separation -Basics-
Table of Content History of magnets... 3 Basics... 5 Exploitation and processing... 10 Resources and demands... 12 Development of raw material price... 14 Usage of magnet material... 16 Magnet materials... 18
History of magnets The first records of magnets date back to the ancient Greeks (Thales, ~600BC). Many poets and scholars have dealt with the phenomenon of magnetism (Euripides, Diogenes, Aristoteles,...) In ancient Egypt Cleopatra used magnetic stones as living jewels i.e. in headbands. As in the 11th century the Chinese discovered the magnetic compass a time of exploring the magnet world began.
History of magnets Can garlic demagnetise a magnet? Many prominent scientists have applied for the exploration and exploitation of the magnet technique (e.g. William Gilbert *1544; 1603 or Charles Augustin de Coulomb; *1736; 1806). But a large share of it has been developed by Johann Carl Friedrich Gauss (*1777; 1855). The unit of magnetic flux density was named after him (1 Gauss = 10-4Tesla).
Basics Magnetism of solids Is caused by the sum of all atomic magnetic moments. Atoms with certain uncompleted electron shells behave like magnetic dipoles. Important reasons for this phenomenon are the spin moments (self-rotation of the electrons) and the shell moments (rotational motion of the electrons around the nucleus). a) Non-magnetic condition: If the moments of many atoms are linked together this leads to measurable results of an external magnetic field. Well-known example is the natural mineral magnetite. b) Magnetic condition: Magnetism is the characteristic of a material to attract magnetically conductive materials. One calls these materials ferromagnetic materials.
Basics Important terms around magnetic separation Operating temperature: Maximum temperature a magnet is allowed to be exposed to without a irreversible loss of performance occuring.
Basics Important terms around magnetic separation Remanence: Remaining flux density after the magnetisation process. Energy product BH max : A measure of the stored magn. energy. Calculated as the highest possible mathematical product of the flux density B and magnetic field strength H
Basics Important terms around magnetic separation Magnetic field & pole area: The strength and direction of magnetic forces can be represented graphically by field lines. The surface areas, which are traversed by the majority of the magnetic field lines are called the pole areas.
Basics Important terms around magnetic separation Coercive force: Strength of a demagnetizing field. The larger this value, the better the material retains its magnetic property (e.g. iron ~0,2kA/m; Neodymium >955kA/m) Permeability µ: Magnetic conductivity of a material. Provides information on how well the magnetic flux is conducted. (Luft ~1; Eisen ~300...300.000) Gauss: Unit for magnetic flux (1 gauss = 10-4 Tesla)
Exploitation and processing 97% supplied by China; thereof 75% from Bayan Obo Mine further mines in Australia, USA, South Africa, Russia, a.s.o. Monazit Bastnäsit
Exploitation and processing
Resources and demands global resources will last for hundreds of years however, sometimes only low contents of rare earth elements also sometimes difficult and costly recovery
Resources and demands 2012-2015 China will barely cover their own needs drastic reduction in the volume of exports by China therefore strongly rising prices Roskill Consulting, Stand: 09/2010
Development of raw material price Raw material price Neodym (China)
Development of raw material price Roskill Consulting, Stand: 09/2010
Usage of magnet material
Usage of magnet material Frontier Rare Earth, Stand: 2008
Magnet materials Strontium-Ferrite: Used for simple applications and for economical solutions. Good performance over a distance. Remanence: max. operation temperature: app. 4000 gauss app. 220 C (428 F)
Magnet materials Neodymium NdFeB: Alloy from neodymium, iron, boron and some other alloying components. At the moment the strongest magnetic material that can be manufactured in a economical way Remanence: app. 13700 gauss max. operation temperature: app. 100 C (212 F)
Magnet materials SmCo: Samarium-cobalt is also a rare earth combination (like NdFeB). It s main use in the separation is for high-temperature applications. Remanence: max. operation temperature: app. 10400 gauss app. 350 C (662 F)
Magnetmaterialien
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