Carburize

Carburizing, also known as carburization, is a heat treatment process in which iron or steel absorbs carbon while the metal is heated in the presence of a carbon-bearing material, such as charcoal or carbon monoxide, with the intent of making the material harder. This process is used to increase the carbon content of the surface layer of the metal, thereby increasing its hardness through the formation of martensite.

Process

Carburizing is typically carried out at a temperature within the range of 900 to 950 degrees Celsius. In this heat treatment process, the steel is heated in an environment rich in carbon. The carbon atoms diffuse into the surface of the steel, forming a high-carbon steel surface while maintaining a tough and ductile interior. There are several methods of carburizing, including pack carburizing, gas carburizing, and liquid carburizing.

Pack Carburizing

In pack carburizing, components are packed in an environment with a high carbon content, such as charcoal or carbon-bearing material, and heated. This method is suitable for low production volumes.

Gas Carburizing

Gas carburizing involves the steel being exposed to a carbon-rich gas atmosphere, typically derived from propane or methane. This method allows for precise control over the carbon content of the surface.

Liquid Carburizing

Liquid carburizing involves the steel being submerged in a carbon-containing salt bath. This method can achieve greater depths of carbon penetration.

Applications

Carburizing is commonly used in the manufacture of gears, fasteners, and other components where a hard surface is required to resist wear, while a tough core is necessary to withstand the impact loads. It is a critical process in the fields of automotive engineering and machinery manufacturing.

Advantages

The main advantage of carburizing is the ability to increase the surface hardness of low-carbon steels while maintaining the strength and toughness of the core. This results in components that have a high resistance to surface wear while also being able to absorb significant impact without fracturing.

Disadvantages

One of the main disadvantages of carburizing is the potential for dimensional changes and distortions due to the high temperatures at which the process is carried out. Additionally, carburizing can increase the risk of cracking in the material if not properly managed.

See Also

• Heat treatment
• Case hardening
• Tempering (metallurgy)
• Quenching