Kontaktipakastus

Kontaktipakastus is a Finnish term that translates to "contact freezing" or "contact tempering" in English. It refers to a heat treatment process used primarily in the metalworking industry to improve the hardness and wear resistance of specific areas of a metal component. Unlike through-hardening where the entire object is heated and quenched, kontaktipakastus involves selectively heating only the surface layer that requires enhanced properties.

The process typically involves rapidly heating the desired surface area using methods like induction heating or flame heating. Once the target temperature is reached, the heated section is immediately quenched, usually in a liquid medium such as oil or water. This rapid cooling transforms the microstructure of the surface layer to a harder, more brittle state, such as martensite. The core of the component remains relatively unaffected, retaining its original ductility and toughness.

Kontaktipakastus is advantageous when only specific wear surfaces or functional areas of a part need to be hardened, while maintaining the overall strength and shock resistance of the bulk material. This selective hardening helps to prevent distortion and cracking that might occur with through-hardening. Common applications include hardening gears, shafts, cutting tools, and other components subjected to high surface stress and abrasion. The precise control over the heating and cooling rates is crucial for achieving the desired hardness profile and preventing undesirable microstructural changes.