Karburaatiossa

Karburaatiossa, often referred to as carburizing in English, is a thermochemical heat treatment process used to harden the surface of steel. The primary objective is to increase the carbon content of the steel's surface layer, creating a hard, wear-resistant case while maintaining a softer, tougher core. This differential hardening is achieved by exposing the steel to a carbon-rich atmosphere or solid medium at elevated temperatures, typically between 800 and 1000 degrees Celsius.

The process involves diffusing carbon atoms into the steel's surface. This can be accomplished through various methods. Pack carburizing uses a solid carbonaceous compound packed around the steel parts in a sealed container, heated in a furnace. Gas carburizing utilizes a hydrocarbon gas, such as propane or natural gas, which decomposes at high temperatures to release carbon. Liquid carburizing employs molten salt baths containing carbon-rich compounds.

Following the carburizing stage, the steel is usually quenched in oil or water to rapidly cool and harden the high-carbon surface. A subsequent tempering operation may be performed at a lower temperature to reduce internal stresses and improve toughness. The depth of the hardened case and its carbon concentration are controlled by factors such as temperature, time, and the composition of the carburizing medium. Karburaatiossa is widely used for components requiring high wear resistance and strength, like gears, bearings, and crankshafts.