Jälkikarkaisulla

Jälkikarkaisu, also known as tempering, is a heat treatment process applied to hardened steel. It is performed after the steel has undergone hardening, which typically involves heating to a high temperature and then rapidly cooling. Hardening makes the steel very hard but also brittle. Jälkikarkaisulla is used to reduce this brittleness and increase toughness, making the steel more usable for various applications.

The process involves reheating the hardened steel to a temperature significantly below its critical transformation point, followed by cooling. The exact temperature and holding time are crucial and depend on the specific type of steel and the desired properties. Higher tempering temperatures result in lower hardness and higher toughness, while lower temperatures retain more hardness but offer less improvement in toughness.

By controlling the reheating temperature, metallurgists can tailor the balance between hardness and toughness in the steel. This allows for the creation of materials suitable for a wide range of tools, machine parts, and structural components where both strength and resilience are important. Without jälkikarkaisulla, hardened steel would be prone to cracking and fracture under stress. The process essentially relieves internal stresses introduced during hardening.