Kovettumiskäsittelyillä

Kovettumiskäsittelyillä refers to a group of heat treatment processes used in metallurgy to increase the hardness and wear resistance of metal parts, particularly those made of steel. These treatments typically involve heating the material to a specific temperature, holding it there for a period, and then rapidly cooling it to achieve a hardened microstructure. The primary goal is to transform the softer, more ductile phases of the metal into harder, more brittle ones.

There are several types of kovettumiskäsittelyillä, each with its own nuances. The most common is quenching, where the heated metal is immersed in a cooling medium such as water, oil, or brine. The choice of cooling medium and its temperature significantly affects the cooling rate and, consequently, the final hardness. Another related process is tempering, which is often performed after hardening to reduce the brittleness and internal stresses introduced during quenching. Tempering involves reheating the hardened metal to a lower temperature than the hardening temperature and holding it there before cooling, which allows some of the hardness to be sacrificed for increased toughness.

Case hardening is another important category. These treatments selectively harden only the surface layer of a metal part, leaving the core relatively soft and ductile. This is particularly useful for components that require a hard, wear-resistant surface but need to withstand impact loads without fracturing. Common case hardening methods include carburizing, where carbon is diffused into the surface of low-carbon steel, and nitriding, where nitrogen is diffused into the surface. These processes are critical in manufacturing components for the automotive, aerospace, and machinery industries where durability and performance are paramount.