GOLD MELTING MACHINE
Gold is an element having atomic
number 79 and belonging to the transition group 11 of the periodic table.
It’s shiny, metallic and melts easily
into bars coins or jewellery. It does not rust, corrode or decay.
Through the history gold has been
seen as symbol of power, beauty purity and accomplishment. Thus gold is very
important at the same time very costly commodity.
In earlier days and even now in small
shops gold is melted using coal furnace (pit furnace) or by gas furnace and gas
torch based on propane, oxy Acetylene or natural gas.
WHAT IS A GOLD MELTING MACHINE?
Gold melting machine is a furnace
that utilises electricity to melt gold.
These machines are divided on the
basis of the principle on which they work. There are mainly three types of
electric gold melting machines
1.
working
on principle of resistance
2.
Working
on principle of induction heating
3.
Working
on principle of microwave heating
Gold melting furnaces produces the
heat by transforming alternating current into heat or radiation directed onto
the Crucible or directly in the gold.
These machines do not emit any type
of gaseous by-product eliminating the harmful pollutants and protecting the
Gold from contamination.
Also the heat is supplied uniformly
while keeping precise control of the temperature which saves energy and melts
the gold very quickly.
ELECTRIC RESISTANCE FURNACE
Electric resistance furnace works on the principle of joules
heating or ohm’s heating.
The heating is done by the first heating
of the heating element, that is kanthal or nichrome coil to red hot temperature,
after which heat is transferred via radiation to the Crucible thus to the gold.
For using electric furnace a highly heat
conductive crucible having high thermal shock resistance and low coefficient of
thermal expansion is preferred.
Gold in an electrical furnace usually
takes a few minutes for the melting to complete.
Though very efficient, electric
furnace cannot be used for continuous casting and for large scale melting. It
needs to be cooled after few hours of operation as longer operation can damage
the heating coil.
Also electrical furnace cannot be
used for heating materials beyond a certain temperature that is about 1200
degrees Celsius.
ELECTRIC INDUCTION HEATING FURNACE
Electric induction furnace works on the principle of electric induction (Lenz law) where in the
heating is generated within the gold itself and there is no heating of the
Crucible.
Electric induction is the most
efficient and Safest way of melting gold and can also be used for continuous
casting processes which is highly desirable for large scale firm or jewellery
industries.
Induction furnace also facilitates
auto stirring and can melt high melting point metals such as platinum.
The one time installation cost of
induction furnace is quite high which makes it unattractive for small jewellery
workshop.
Talking about the Crucible, depending on the frequencies different Crucible material can be used, also there are self frequency changing induction machine in which different Crucible can be used and different material can be melted without any modification.
See our induction furnace in action ,
ELECTRIC MICROWAVE FURNACE
Microwave furnace works on the
principle of molecular heating of the element using microwave having frequency
of about 2.4 GHz which is generated by the use of magnetron.
Magnetron is a vacuum tube in which
high energy is created due to the field charge and is directed through a
waveguide into the microwave chamber where the material is placed.
Different from other forms of heating
microwave heating does inside out type of heating of the material that is the
material is heated from within to the outside.
While using microwave furnace for heating
of gold make sure that the magnetron is on the backside and not on the top
side.
Right now, this method is in the
experimental phase used only in the laboratory application; thus, this method
is not suggested for commercial use due to danger of radiation damage and fire
hazard.
This method is highly efficient, cost
effective and very fast but cannot be used for large scale melting.
During melting of gold by any of the
method above if there is a chance of some impurities being dissolved it is
recommended to use flux.
Flux such as sodium carbonate, Borax
can be used; edible soda can also be used.
Flux helps in reducing the melting
point of the material at the same time helps in removal of the impurities
within the gold by making oxides with the impurities and floating on the top of
the liquid metal.
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