/ Copper / Zinc / Lead / Magnesium: Crucible Melters
Crucible melting equipment (sometimes referred to as "pot"
melters) consists of a cast iron, steel or other alloy, or clay bonded graphite
crucible that usually holds between 200 and 3000 pounds of molten material. Many
crucibles are sized in the 500 to 1000 pound melt size. The crucible is surrounded
by a structure where natural gas, or other fuels, is fired into the space between
the crucible and the structure. Electrical elements are also used in this space
to heat (indirectly) and melt the materials in the crucible.
to varying melt capacities, crucibles are produced with several design features
suited for the end-use need. They can be stationary or can be fitted with quick
disconnect devices to allow melting in one location and transport to another for
pouring (most are stationary). They can also tilt to more easily facilitate pouring
into transport ladles to the casting area. Gas fired designs that separate the
flue gas exhaust from coming in contact with the surface of the molten bath and
that utilize covers will result in reduced metal losses and the lowest operating
crucible furnaces are also used for melting copper bearing alloys (brass, bronze,
copper alloys), magnesium, and zinc. Only the pot (or crucible) materials change.
Gas and electric designs exist for all materials. The following series of pictures
illustrate the basic look and design of crucible furnaces.
have historically been perceived as a low-cost but higher metal loss melting option.
Newer designs keep the products of combustion away from the melted materials.
The next two images illustrate available exhaust discharge options:
Also a more
recent development is a "Non-Crucible" furnace. A series of pictures
illustrates features that include:
- Metal is charged
into a dry hearth charging chamber. This eliminates any safety issues associated
with placing cold or moisture bearing charge materials into a molten bath of aluminum.
exhaust energy (to preheat and help melt the new charge)
- Improves metal
quality by leaving slag, dross, and other residuals on the dry hearth where they
can be removed.
- Uses gate
filters and inert gas degassing to assure that only clean filtered aluminum is
available for tapping.