To melt and pour this alloy at between 430-520oC, a rule-of-thumb heating
value of between 1.1-1.4 MJ/kg (500-600 BTU/lb) can be applied. Most processes use the
pressure die casting method and as the temperatures are lower, torch burners or the
compact package type burners with accurate temperature control can be the most suitable.
Package burners incorporate the fan and safety system in a neat unit.
This metal has a working temperature of
around 330-380oC and as the rule-of-thumb factor is quite low at approx. .16 -.35 MJ/kg
(70-150 BTU/lb) an economical, atmospheric burner would be suitable for most smaller
furnaces. These are usually arranged to directly heat the base and sides from underneath
with thermoelectric flame safety and a pilot burner fitted. It is important to include
temperature control to ensure the process does not overheat. Larger capacity furnaces
would utilise the nozzle mixing or premixing burners with automatic controls. Please ask
for the relevant data.
Frequently during the heating process it is necessary to transfer the alloy from the melting area to the processing zone. Transfer tubes or launders need to be heated to ensure the metal does not solidify.
GOLD AND SILVER
With small quantities of gold to melt a simple air/gas premix torch burner can be used utilising a compressed air supply or air from a small blower. Gold has melting and pouring temperatures of approx. 1070oC and 1180oC. Silver is worked at lower temperatures, approx. 960oC to melt and 1060oC to pour. Premix or nozzle mix burners are used for larger quantities and industrial applications.
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