täyshehkutuksessa

Täyshehkutuksessa is a Finnish term that translates to "full annealing" in English and refers to a heat treatment process used on metals. This process is primarily applied to ferrous metals, such as steel, to improve their ductility, reduce hardness, and relieve internal stresses.

The process involves heating the metal to a specific temperature, known as the austenitizing temperature, which is above its upper critical temperature. This temperature is held for a sufficient duration to allow the entire workpiece to reach a uniform temperature and for the material's microstructure to transform into austenite. Following the holding period, the metal is cooled very slowly, typically within the furnace, to room temperature. This slow cooling rate is crucial for achieving the desired metallurgical changes.

The slow cooling allows for the formation of ferrite and pearlite microstructures, which are softer and more ductile than the martensite or bainite structures that can form with faster cooling rates. By reducing internal stresses, full annealing makes the metal easier to machine, form, and work with in subsequent manufacturing steps. It is often used as a preliminary treatment before cold working or machining operations. The exact temperatures and holding times vary depending on the specific alloy being treated.