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Ferrocerium is a man-made metallic material that gives off a large number of hot sparks at temperatures at 3,000 °F (1,650 °C) when scraped against a rough surface (pyrophoricity), such as ridged steel. Because of this property it is used in many applications, such as clockwork toys, strikers for welding torches, so-called "flint-and-steel" or "flint spark lighter" fire-starters in emergency survival kits, and cigarette lighters, as the initial ignition source for the primary fuel.
It is also commonly called ferro rod and most commonly of all flint (particularly in cigarette lighters), although it is a successor to the true flint historically used rather than a variety of it. As tinder-igniting campfire starter rods it is sold under such trade names as Blastmatch, Fire Steel, and Metal-Match for survivalists and bushcraft hobbyists. Some manufacturers and resellers incorrectly call them "magnesium" rods. It is also known in Europe as Auermetall after its inventor Baron Carl Auer von Welsbach.
While ferrocerium-and-steels function in a similar way to actual flint-and-steel in fire starting, ferrocerium actually takes on the role that steel played in traditional methods: When small shavings of it are removed quickly enough the heat generated by friction is enough to ignite those shavings. The sparks generated are in fact tiny pieces of burning metal. In traditional flint-and-steel fire-starting systems (using actual flint), it is the tiny shavings of the steel removed in the striking process that burn, rather than the flint. The sparking is due to cerium's low ignition temperature of between 150 and 180 °C (302 and 356 °F).
Flint spark lighter
A flint spark lighter (sometimes just called a spark lighter, striker, or flint lighter) is a type of lighter used in many applications to safely light a gaseous fuel to start a flame. It is most commonly used for bunsen burners and oxyacetylene welding torches.
A flint spark lighter works by rapidly rubbing a small piece of ferrocerium against a rough steel surface (also called the rasp), in much the same way flint and steel are used. This manual rubbing action, done by squeezing the handle, creates a spark which then lights the gaseous fuel.
The mechanical properties of rare earth metals can be adjusted to optimize spark production. These strategies have been developed to make such alloys more brittle:
- Oxide - most contemporary flints are hardened with 20% iron oxide and 2% magnesium oxide.
- Intermetallic - in the Baron von Welsbach's original alloy, 30% iron (ferrum) was added to purified cerium, hence the name "ferro-cerium". Iron reacts with rare earth metals to form hard intermetallic compounds similar to those in neodymium magnets; such magnets are also known to generate sparks quite easily when broken.
There were actually three different Auermetalls developed: The first was just iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals.
A modern ferrocerium firesteel product is composed of an alloy of rare earth metals called mischmetal (containing approximately 50% cerium, 25% lanthanum, and small amounts of praseodymium and neodymium), plus iron and a small amount of magnesium:
- Jorgenson, John D.; Corathers, Lisa A.; Gambogi, Joseph; Kuck, Peter H.; Magyar, Michael J.; Papp, John F.; Shedd, Kim B. "Minerals Yearbook 2006: Ferroalloys". United States Geological Survey. Retrieved 2009-04-24.