Carburizing, also known as carburizing, is a process of introducing carbon into the surface layer of steel to impart certain mechanical and physical properties. This process is mostly done by heating the steel to an elevated temperature, then introducing carbon or other suitable alloy element gas into the steel. A carburizing reaction, also known as a decarburization reaction, is a chemical reaction that occurs when a metal oxide is mixed with carbon or a carbon-bearing compound. The reaction results in a decrease in the amount of carbon in the metal, which is known as decarburization.
Carburizing is commonly used for alloy steels and stainless steels, as well as for titanium and other metals. It is done to increase the wear resistance and toughness of the steel and to improve its corrosion resistance. The process also helps to create an excellent surface finish.
Carburizing is typically done at temperatures of 900-1050°C and involves introducing carbon-bearing gases in the form of either acetylene, propane or natural gas. A furnace with a pre-heating and cooling chamber is used to maintain the temperature and atmosphere. A thermocouple is used to measure the temperature and a carbon potential controller is used to adjust the gas mixture.
When in a furnace, the steel that is being carburized is exposed to a particular atmosphere containing, for example, mixed gases of carbon monoxide, carbon dioxide, and nitrogen. These mixed gases serve as a source for the diffusion of carbon atoms into the steel, where it replaces a small amount of the iron atoms in the steels bonding structure. This results in a carbon-rich surface layer that hardens from stress and improves wear resistance, fatigue strength, and corrosion resistance.
At the same time, the metal’s internal grain size and toughness also increase due to the refinement brought about by the carburizing reaction. The internal grain size determines the metal’s strength. The grain size inside the metal can be made relatively smaller and even finer by the presence of carbon atoms, making the metal stronger.
Carburized metal must then be quenched to cool it rapidly and prevent it from softening due to its new crystal structure. This quenching process helps to produce a higher hardness, better wear resistance, and greater strength in the metal.
In order to maximize the benefits of carburizing, metallurgical controls should be kept tight, with a consistently monitored environment. The process may also be combined with additional finishing such as shot peening or spheroidizing, and nitriding, in order to achieve certain specific properties.
Carburizing is an important process for producing parts and components with desired mechanical and physical properties. It helps to improve the wear resistance, toughness, and corrosion resistance of the metal, as well as to modify its internal structure for increased strength and toughness. The quenching step is important to properly complete the carburizing process in order to achieve the desired result.
