Retained austenite content
Residual austenite content is the amount of face-centered cubic crystal lattice that remains in the microstructure at room temperature after incomplete martensitic transformation. High austenite content can impair dimensional stability and cause austenitic transformation through deformation.
Physicochemical mechanism of action
After welding, the metal is often held in a face-centered cubic crystal lattice (austenite). During incomplete martensitic transformation, some of this austenite remains in the microstructure when it cools to room temperature.
Metallurgical relevance & risks in welding
A high retained austenite content can impair the dimensional stability of the material. Due to mechanical deformation, this austenite can transform martensitically, leading to further deformation and possibly cracking. This is especially a problem in rigid steels.
Workshop practice & action instructions
To minimize retained austenite, the weld should cool as quickly as possible to achieve complete martensitic transformation. This can be achieved by choosing the right welding process and the correct cooling strategy. For rigid steels, it is important to keep the austenite content below 1% to ensure a stable and crack-free weld.