Temperálás

Temperálás is a heat treatment process used to modify the mechanical properties of metals and some glasses by controlled heating and cooling after prior processing such as hardening. The aim is to reduce brittleness, relieve residual stresses, and achieve a desired balance of hardness, strength, and toughness suitable for the intended use.

In steel, tempering follows quenching. The material is heated to a temperature within a specific range, typically roughly 150–650 °C depending on alloy and desired properties, held for a time, and then cooled in air, oil, or another medium. The tempering temperature influences carbide precipitation and the transformation of martensite, producing tempered martensite. Higher tempering temperatures generally increase toughness and ductility but lower hardness, while lower temperatures retain more hardness at the expense of toughness.

The resulting microstructure is a softer, more ductile phase with redistributed carbon and carbide particles, reducing internal stresses and improving impact resistance. The specific tempering regime is chosen to meet functional requirements such as wear resistance, fatigue strength, or dimensional stability.

Tempering is not exclusive to steel. Tempering of glass, for example, involves heating the glass to a high temperature and then rapidly cooling it to create compressive surface stresses, greatly increasing strength and thermal shock resistance. While the underlying principles differ among materials, the common goal across tempering processes is to tailor properties by controlled thermal treatment rather than by mechanical work alone.

Quality control for temperálás typically includes hardness testing, impact testing, and microscopic examination to verify the expected balance of hardness and toughness and to ensure that residual stresses are within acceptable limits. Improper tempering can lead to cracking, distortion, or insufficient performance in service.