Precipitation Hardening
Precipitation hardening increases the hardness and tensile strength of a steel through finely dispersed, coherent precipitates of a second phase. These hinder the movement of dislocations.
Physico-chemical mechanism of action
Precipitation hardening occurs when a second phase forms in a metal during cooling and is finely distributed throughout the lattice. This second phase can consist of various elements, such as carbon or silicon. It forms coherent precipitates that fit into the metal and affect its structure.
Metallurgical relevance & risks during welding
Precipitation hardening can lead to increased hardness and tensile strength, which is especially desirable for high-performance steels. However, it can also lead to cracks and hot cracks if cooling is too fast or if the additives are not processed correctly. An insufficient melting process can cause the second phase to not be distributed adequately, which in turn impairs hardness and strength.
Workshop practice & instructions for action
To successfully use precipitation hardening, it is important to carefully control the melting process. This includes correct selection of additives and adherence to proper cooling steps. Too rapid cooling can lead to cracks, while too slow cooling can reduce hardness. It is recommended to measure and control the cooling time in seconds and the temperature in the critical temperature window (t8/5) precisely.