Crucible melting and cupola operation are two types of melting processes that are used to melt down the solid substances for analytical needs.
What is Crucible Melting?
Crucible melting is the process of melting down solid substances in a furnace that is made of ceramic material. These are among the oldest and most common furnaces worldwide. This type of furnaces contains a refractory crucible made of ceramic and it contains the metal charge (the solid substance that is going to be melted). The crucible melting process is important in the production of small batches of alloys having low melting points.
During the crucible melting process, the metal charge is melted down via the conduction of heat through the crucible walls. The most common heating fuels for these furnaces are coke, oil, gas, and electricity. The buildup of a crucible melting furnace is simple compared to other furnaces. The container in the crucible can withstand very high temperatures. Therefore, it can be used to melt metals.
What id Cupola Operation?
Cupola operation is the process of melting down solid substances in a cupola furnace. It is a vertical and a cylindrical furnace that is used mainly for the melting of iron forms such as cast iron, N-resistant iron and some bronze types.
A cupola furnace can be made in any practical size depending on the requirement. However, the size of a cupola furnace is given in its diameter. E.g. three feet cupola furnace. The vertical and cylindrical furnace is aided by four legs to keep it vertical. Therefore, the overall look of this furnace is similar to a large smokestack.
In the construction of the cupola operation, the furnace has a semi-open lid to prevent rainwater entering the furnace and to allow gases to pass through. At the bottom of the furnace, there are fitted doors that can swing down. In order to remove the total emission from this furnace, there is a cap that can pull emitting gases into a separate system which can cool and remove particulate matter. The cupola furnace is made of steel, refractory brick and plastics. The plastic material is a lining for the furnace. However, the bottom of the furnace is lined with clay and sand mixture.
At the beginning of the cupola operation, the furnace has to be filled with a layer of coke. Then the coke layer is ignited with a torch. Thereafter, the air is introduced into the furnace. When the coke reaches a very high temperature, solid pieces of the metal to be molten is inserted from the top of the furnace. Here, limestone is useful as a flux. The molten metal drips down the furnace though coke and it gets collected in a pool at the bottom of the furnace.
What is the Difference Between Crucible Melting and Cupola Operation?
The key difference between crucible melting and cupola operation is that crucible melting requires a furnace made of ceramic, whereas cupola operation uses steel for the preparation of the furnace. Moreover, in crucible melting, the metal is melted at the bottom of the crucible while in cupola melting, the metal is melted on the coke and drip down to the pool of molten metal at the bottom of the furnace. So, this is another difference between crucible melting and cupola operation.
Summary – Crucible Melting vs Cupola Operation
Crucible melting and cupola operation are two types of furnaces that can be used to melt solid substances. The key difference between crucible melting and cupola operation is that crucible melting requires a furnace made of ceramic whereas cupola operation uses steel for the preparation of the furnace.
1. “Cupola Furnace.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 18 Oct. 2007, Available here.
2. “What Is A Crucible Furnace?” Flamefast, Available here.
3. “Cupola Furnace.” Wikipedia, Wikimedia Foundation, 8 Mar. 2020, Available here.
1. “Czochralski method used crucible 1” By Twisp assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (Public Domain) via Commons Wikimedia
2. “Cupola Furnace Iron” By Ab5602 (talk) – Own work (Original text: I created this work entirely by myself.), Public Domain) via Commons Wikimedia