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Name: Heath
Status: Other
Grade: Other
Location: FL
Country: N/A
Date: June 2005


Question:
What type of metal is used when melting other metals, example... when melting iron and other kinds of strong metals they use a scoop that go's into a huge oven, why does the scoop not melt too?



Replies:
Heath,

The material used in smelting belong to a class of materials called ceramics. Ceramics usually have very high melting points (if they show any at all). If we were to look at the way the atoms are arranged between a metal and a ceramic, we start getting an idea as to why this is so. Imagine a row of marbles. On top of this row, place another row of marbles. And then on top of that, another row. You can easily imagine that each row can slide sideways so that not one particular marble really is exclusively always on top of another particular marble. This is the way metals are. This is what gives metals their malleability and ductility - and which also allows them to melt at achievable temperatures. Ceramics on the other hand are built differently. Imagine our set of marbles again, but this time, make sure that the marbles in each column are directly on top of each other, and then in the gaps formed by every set of four marbles (right in the center of a square of marbles), we place a smaller marble that just fits exactly within that gap. Such an additional "atom" will prevent the slippage from side to side. You can imagine that this denser packing will make the material harder and less prone to melting.

Greg (Roberto Gregorius)


Heath,

The key is to choose a material for the scoop that has a melting temperature higher than the temperature of your furnace (which is set to the melting temperature of the metal you want to melt). For most high temperature furnaces it is not another metal that used, it is a type of ceramic. A ceramic is a material that is inorganic, insulating, and an oxide, carbide, or nitride. Some examples include: Al2O3 (aluminum oxide)--has a melting temperature of 2050 degrees Celsius, MgO (Magnesium oxide)--melting temp is 2800 degrees C, and SiC (silicon crbide)--melting temp 2500 degrees C.

Compare these melting temperatures to the melting temperature of iron or steel which is only around 1500 degrees C or 2800 degrees F! No problem. Ceramics are great!

Ceramics tend to me very hard, very stiff, but very brittle.

The one drawback of ceramics that comes to mind when talking about steel is that you have to be very careful which one you try to use to cut hot steel. You cannot use anything with carbon in it to cut hot steel, because it leaves some of the carbon behind, which makes the steel less strong. You cannot use diamond---diamond is made out of carbon, too. There is been a lot of work recently in the field of material science to develop materials for industrial applications like this.

Michelle Weinberger


The Crucible, or "scoop" is typicly made of materials with extraordinarily high melting points, or none at all. I have heard of crucibles being made of ceramics and Granite.

Ryan Belscamper



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