Raitajäähdytys

Raitajäähdytys, also known as temper or tempering, is a process in metallurgy where a hardened steel is reheated to a specific temperature below its critical point and then cooled. This process is performed after quenching, which makes steel very hard but also brittle. Tempering reduces the brittleness by allowing some of the trapped stresses to relax and by forming more stable microstructures. The specific tempering temperature chosen directly influences the final properties of the steel, affecting its hardness, toughness, and ductility.

Lower tempering temperatures, typically between 150-300 degrees Celsius, result in a material that retains a significant portion of its hardness while gaining increased toughness. This is often suitable for tools and cutting edges that require both sharpness and resistance to chipping. As the tempering temperature increases, the steel becomes progressively softer and more ductile, but its hardness decreases. Higher tempering temperatures, up to around 600 degrees Celsius, yield a much tougher and more ductile material, which is desirable for components subjected to significant impact or bending forces, such as springs or structural parts.

The cooling rate after tempering can also play a role, though it is generally less critical than the tempering temperature itself. For most applications, slow cooling in air is sufficient. The precise temperature and duration of tempering are determined by the specific type of steel and the desired balance of mechanical properties for its intended application. This controlled reheating and cooling cycle is essential for achieving the optimal performance and reliability of hardened steel components.