uunikovetus

Uuunikovitus, or furnace hardening, is a heat treatment used to increase the hardness and wear resistance of metal parts by heating them in a furnace to a high temperature and then rapidly cooling them. The goal is to transform the steel’s microstructure, typically to martensite, to achieve a harder finished part. The process is commonly applied to carbon and alloy steels that have sufficient hardenability.

The typical sequence involves cleaning the workpieces, placing them in a controlled furnace, and heating at a chosen rate to the austenitizing temperature, usually around 800–900°C for many steels. The parts are held at that temperature for a soak time determined by thickness and alloy composition, then quenched rapidly in oil, water, or another quench medium. After quenching, the part is often tempered at a lower temperature to reduce brittleness and adjust toughness and hardness.

Through-hardening is a common goal of furnace hardening, where the entire cross-section is hardened. Some furnace-based processes, however, are used for surface hardening, such as carburizing, nitriding, or carbonitriding, which create a hard outer layer while preserving a tougher core.

Materials suitable for uuunikovitus include many carbon and alloy steels with adequate hardenability. Stainless steels and certain high-alloy grades may require alternative heat treatments. Quality control typically involves hardness testing, microstructure examination, and distortion checks, with attention to quenching speed and uniform cooling to minimize cracking and warping.

Applications include gears, shafts, cutting tools, bearing surfaces, and other components demanding high surface or through hardness and wear resistance.