How Does a Gas Carburizing Furnace Work?


In order to create carbon steel or other metals with carbon, a carburization process is used. In the past, case hardening was used to infuse carbon into metal. This was accomplished by packing the metal with charcoal. In some cases, other materials like urine, salt or leather were used. Today’s methods utilize gases, and a gas carburizing furnace is one of the most effective methods. Let’s take a closer look at carburizing and the carburizing furnace and see how it operates.

Why Add Carbon?

Adding of carbon to metals like steel makes the steel harder and less brittle. This not only makes steel stronger but less likely to crack under stress. When carbon content is controlled, the amount of hardness is also controlled.

The Carburizing Process

The purpose of carburizing is to add carbon to heated metal. This is accomplished by providing an atmosphere which is very high in carbon. It is important for the air to be free of other materials which may contaminate the metal in the process. This is why a controlled atmosphere is created by a carburizing furnace. In fact, a vacuum method is usually employed to purify the environment.

The gas carburizing furnace uses carbon monoxide (with its high carbon content) to diffuse carbon atoms to hot metal. When hot steel is exposed to a carbon rich environment, atoms of carbon are literally diffused into the material. The longer the metal is left in this atmosphere, the more carbon it will absorb.

It is very important to monitor and control the atmosphere of the carburizing furnace during the entire process. This will provide the desired carbon content for the metal. After the heated metal is carburized, it is rapidly cooled to lock the carbon into the material. The modern gas carburizing furnace is capable of performing both carburizing and quenching.

The Importance of Carbon Potential

Carbon potential is the ability of the atmosphere to transfer carbon to materials, and this needs to be monitored by the gas carburizing furnace. However, it is not easy to measure and maintain control of carbon content. In fact, because there are no methods to directly measure carbon, an indirect method must be utilized. This can be done with oxygen sensors or gas dewpoint measurements.

Low-Pressure Gas Carburizing Furnace

Low pressure carburizing is becoming more and more popular because of the many benefits it provides. It uses a vacuum furnace with low pressure and higher than normal carburizing temperatures. This increases hardness control, and there is no oxidation. Plus, it is more environmentally friendly than standard methods as carbon dioxide emissions are greatly reduced.

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