Precipitation hardening
Precipitation hardening occurs from finely dispersed, coherent precipitates in the metal matrix that hinder dislocation movement and increase strength.
Physico-chemical mechanism of action
Precipitation hardening occurs when a second phase forms in the metal and is firmly anchored in the matrix. These precipitates can arise from various causes, such as cooling or chemical changes. They hinder dislocation movement within the metal and lead to increased strength.
Metallurgical relevance & risks during welding
Precipitation hardening can occur with insufficient cooling or a missing precipitation process. It leads to increased hardness and toughness of the weld seam, which can lead to cracks and fractures. It is important to control the precipitation process during welding to ensure uniform cooling.
Workshop practice & instructions for action
To avoid precipitation hardening, the cooling of the metal after welding should be controlled and slow. This can be achieved by using cooling water or cooling gas. The temperature should not drop too quickly to ensure uniform precipitation. For hardenable steels, it is especially important to monitor the precipitation process and regulate cooling.