< KILN & CASTING SUMMARY
KILN & CASTING KEYWORDS
BURNOUT: The evacuation of wax in investment moulds via flame. The burnout may be combined with firing in a continuous kiln operation. Burnout is also often referred to as a DE-WAX (esp US).
CENTRIFUGAL CASTING: Means of forcing a charge into a refractory mould by rotating the mould in a centrifuge. Typically a small scale precision casting technique.
CHARGE: A quantity of metal alloy for decanting into refractory moulds.
COVER FLUX: A flux coating placed over a molten charge, functions as a barrier to gas contamination and also consolidates DROSS material.
CRUCIBLE: Refractory container (usually composed of graphite material), used to contain the metal charge during melting and pouring procedures.
DROSS: Oxidised film and other contaminants (including cover flux), which float on the surface of a melted charge. Usually removed by skimming off before mould pouring. Entry of dross into a mould often leads to inclusion faults.
ELECTRIC INDUCTION: A furnace that melts a charge by inducing a current in the charge via a high frequency electrical coil. Typically produces a very clean melt, suitable for high melting point special metals and alloys (nickel, stainless steels etc).
ELECTRIC RESISTANCE: A furnace that melts a charge by radiating heat via an electric element. Usually only suitable for low melting point metals and alloys (aluminium, zinc etc).
FIRING: Heating of the investment mould to dry out and modify the refractory’s structure. Chemical changes enable the mould to attain full strength and maximum thermal resistance.
FLASH DE-WAX: Rapid evacuation of wax from a [ceramic shell] investment mould by exposure in a pre-heated kiln.
GREEN: The condition of a material prior to attaining it’s full working properties, usually refers to un-fired investment moulds as well as other refractory materials.
INCLUSION: Non-metallic contamination of a cast, usually caused by loose investment, sand or dross entering the mould cavity before or during the pour.
LADLE: An alternative container to a crucible for a furnace decanted charge. A ladle may be a hand held bowl somewhat similar in appearance to a soup ladle, but more usually refers to a large container for pouring quantities of metal. Most large ladles are geared to allow easy dispensation of the metal charge into a mould.
MISCAST: A failed or incomplete cast (see also MIS-RUN).
MISRUN: Failure to fully fill a mould. Normally due to too small a cavity air gap, or the result of back pressure in the mould.
RETURNS: Off-cuts from previous casts returned to partially charge the furnace. Should not normally exceed 25% of total charge composition by weight.
SCAVENGING AGENT: A material added to a metal charge which has a powerful de-oxidising effect (most commonly zinc, silicon, phosphorous etc).
SHORT RUN: Incomplete filling of a mould due to the pouring of an insufficient quantity of metal.
VACUUM CASTING: Means of assisting metal flow into intricate moulds by applying a full or partial vacuum force.
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