Metallographic diagram of 20 steel (920℃) carburized treatment

Carburizing is a process by which a case layer of carbon rich material is diffused into the surface of steel components. The primary functional benefits are improved wear resistance and greater fatigue strength. The steels most widely used for carburizing are plain carbon steels (high, medium and low carbon) and some low alloy steels. It is carried out in two mutually exclusive cycles: ‘pack’ carburizing and gas carburizing. The difference between the two processes is the method of introduction of the carbon into the surface of the steel. In the pack carburizing the carbon is in solid form (carbonaceous solids). The solids are mixed with a carrier ( usually coal dust mixed with a binder ) to form ‘packs’ which can be applied directly to the components. The components are heated in a powered furnace for several hours. As the temperature rises above 900°C, the carbon contained in the solid material diffuses into the surface of the steel, killing off surface decarburization in the process. In gas carburizing, a gaseous form of carbon (carbon monoxide, propane, methane, natural gas) is passed through a heated chamber containing the steel components. The carbon combines with surface iron, forming iron carbide (cementite) which gives the case layer below 5/1000th) to 10/1000ths of an inch improved properties.

The process of carburizing 920 steel components at 920℃ involves quenching and tempering of the parts. This process is carried out in order to improve the strength and the wear resistance of the steel components. Quenching and tempering involves the components being heated to a temperature between 895 and 905℃ and then cooled quickly in oil or warm water. This sudden cooling increases the hardness of the steel, giving it improved properties in terms of tensile strength, fatigue strength and wear resistance. After quenching and tempering, the surface of the components is inspected for surface decarburization. If any surface decarburization is found, the components are usually re-hardened and, if necessary, re-tempered.

For the carburizing of 920 steel components at 920℃, the packs used will typically consist of a carbonaceous material such as coal dust or coke, a binder such as beeswax, and an insulation material such as bentonite or graphite. The components are heated in a carburizing furnace to a temperature of 920℃. The components are then left in the furnace for a predetermined period of time and then quenched in oil or warm water. The amount of time needed in order to reach the desired case depth depends on the grade of steel, the carbon content, and the pre-heat time. Once the components have been quenched and tempered as required, they are then inspected for surface decarburization. If any surface decarburization is found, the components are re-hardened and, if necessary, re-tempered.

The microstructure of the case and core of 920 steel carburized at 920℃ typically consists of a martensitic matrix of varying hardness and toughness. This can be seen in the micrographs provided with this article. The matrix may contain small amounts of complex of ferrite, pearlite, and bainite which can be seen at higher magnifications. The carbon content of the case material is typically greater than 1.00%, and the carbon content of the core is between 0.30–0.70%. The case hardness and core hardness can also be seen in the micrographs. The case hardness typically ranges from 50-60 HRC, while the core hardness typically ranges from 30-40 HRC.

In conclusion, the carburizing of 920 steel components at 920℃ is an effective means of improving thewear resistance and strength of steel components. The process involves the introduction of carbon into the surface of the steel components, resulting in a case layer below5/1000th to 10/1000ths of an inch with superior properties. The microstructure of the carburized components is a martensitic matrix of varying hardness and toughness with small amounts of ferrite, pearlite, and bainite. The case material typically has a carbon content of greater than 1.00% and the core hardness typically ranges from 30-40 HRC.

This is a metallographic image of C20 steel (920℃) that underwent carburizing treatment. The surface of the steel is of a light gray color, indicating that the steel has a high concentration of carbon. This is due to the carburizing treatment, which involves introducing high concentrations of carbon atoms into the steel in order to make it more durable. As the carbon is introduced into the steel, the surface of the steel undergoes a transformation from a light grayscale to a darker hue. This can be seen in the image, where there is a distinct line between the light gray surface and the deeper gray area.

The microstructure of the steel consists of irregular shaped ferrite grains surrounded by a fine grain lath-like martensite structure. These structures are typical of carburized steel due to the introduction of higher concentrations of carbon. This carburizing process changes the microstructure of the steel, making it more resistant to wear and tear. The dark gray color of the ferrite grains reveals that they are highly alloyed and have a high carbon content.

The carburized steel has been successfully treated, as evidenced by the presence of the low carbon content, the fine grain lath-like martensite structure and the high concentration of carbon at the surface. The steel sample has been properly treated to increase its wear resistance, making it suitable for application where a hard and durable material is required. In summary, this metallographic image of C20 steel (920℃) reveals a successful carburizing treatment that has changed the microstructure of the steel and increased its wear resistance.