Precious metals need to be heated in order to be effectively manipulated. This has led to the development of several significant kinds of furnace for the melting an annealing of gold, silver, and platinum. While induction furnaces are by far the most common kind of precious metal melting device, cupola and open-hearth styles are still used by some specialists. This article takes a close look at some of the commonly used kinds of furnace in the precious metalworking industries.
Induction
Induction furnaces are some of the most popular kinds of precious metal melting solution in industrial settings due to their high level of efficiency and accurate control parameters. They can range in size from desktop units to huge multi-ton units. Search for precious metal melting furnace for a rundown of different induction furnace types. Induction furnaces work using eddy current heating. Electrical conductors are wrapped around the heating chamber of the furnace. A strong alternating current is then passed through the conductors, which induces eddy currents in the precious metal contained within the chamber. These currents produce extreme heat—melting the metal. Induction heating is considered to be the most efficient way of heating and melting precious metals in small batches.
Open Hearth
Open-hearth furnaces are rarely used in the refinement of precious metals, but are sometimes made use of in the purification or extraction process. Open-hearth furnaces are designed to burn off carbons—purifying metals slowly while allowing for testing. Open-hearth furnaces are most commonly used in the production of steel using “pig iron” and metalworking scrap. An agent such as limestone usually needs to be added during this process in order to ensure purity. This method was first developed in 1865 in Europe. In Africa, the method was first developed over 2000 years ago by the Haya people in present-day Tanzania. The Haya people still keep the tradition of steelmaking alive through oral traditions.
Cupola
Cupola furnaces look like large smokestacks. They are upright, cylindrical chambers usually supported by four sturdy legs. The bottom of the furnace is equipped with doors that can open out and drop melted materials down into a casting die. Cupola furnaces can be produced in almost any size, making them perfect for small-scale melting operations. In order to light a cupola furnace, operators need to fill the bottom with compressed coke, which is then lit—inducing extreme temperatures in the enclosed space.
Cupola furnaces were first built in China during the Warring States period during the 4th century BC.
Annealing
Annealing is the process of heating a metal beyond its recrystallization point in order to increase its ductility—making it far easier to work with. Advanced precious metal workers may use annealing furnaces in order to soften metals so that they can create intricate designs. Annealing furnaces are able to keep a material heated and stable for long periods of time, and the furnaces used in the present day typically heat metals using alternating current induction.
