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.