1.1248 | C75S HT yes/no

The question was whether this sample had undergone a bainitising (skewed) heat treatment (HT) or whether it was a bad “+AC” initial condition.

The two heat treatment states +I and +AC can be found in separate case studies. In the light microscopic images we see formed carbides, ferrite and very finely in the background also cementite lamellae (perlite). Locally, there are areas that are more brownish etched and where cementite lamellae are no longer visible. In terms of light microscopy, we are at the limit of resolution here. Scanning electron microscope images clearly show the typical, bainitic structure in individual grains. So a heat treatment was carried out in an attempt to achieve a bainitic structure. Even if soft annealing was carried out just above Ac1, a quenching rate with moving air is not sufficient to produce bainite.