Mischmetal
Misch metal , and cerium -Mischmetall is a metal alloy made of rare earth metals . Standard qualities typically consist of at least 98% rare earth metals, 1% iron and 0.8% magnesium .
The mischmetal does not have a fixed melting point, but a melting range that is around 800 ° C, close to the melting point of cerium.
Since the rare earth metals are very difficult to separate because of their great chemical similarity, mischmetal is cheaper than each of these elements and is used with preference whenever possible.
The percentage distribution of rare earth metals in classic mischmetal results directly from that of the starting mineral monazite : it contains about 45 to 52% cerium , 20 to 27% lanthanum , 15 to 18% neodymium , 3 to 5% praseodymium , 1 to 3% samarium , Terbium and yttrium , traces of other rare earth metals. Due to today's high demand for neodymium for the production of neodymium-iron-boron magnets, however, this, and mostly also the elements samarium and the following, are now separated so that today's mischmetal usually only includes the rare earth metals cerium, lanthanum and some Contains praseodymium. Due to the similarity of the chemical properties of the rare earths, deviations in the composition - in applications for which misch metal can be used at all - are mostly uncritical.
Iron-mixed metal alloys with an iron content of 15% to 50% are called cerium-iron or with the trade name Auermetall .
As an additive in steel production, mischmetal reduces unwanted iron oxides , binds oxygen and sulfur and supports degassing . As an alloy metal, it improves the casting and flow properties as well as the corrosion resistance of iron-chromium-aluminum materials in hot oxidizing gases.
Additions of cerium mischmetal improve the mechanical properties of cast iron with spheroidal graphite by compensating for the negative influences of so-called interfering elements on the graphite formation.
The Austrian chemist Carl Auer von Welsbach discovered the pyrophoric properties of iron-mischmetal alloys (patent 1903). Filings ignite in the air - a property that is used in the manufacture of flints for lighters . In the "Auerwerke" (now Treibacher Industrie AG ) founded by him, flint stones are still produced today under the trade name Auermetall .
Individual evidence
- ↑ Treibacher.com: Mischmetall ( Memento from May 11, 2008 in the Internet Archive )
- ↑ http://www.chemieunterricht.de/dc2/lanthan/mischmet.htm