In continuous casting, it’s long been understood that peritectic steels are prone to casting defects. There is plenty of evidence that alloying elements such as manganese play a pivotal role in the quality of continuously cast products. However, there is still no general understanding of the fundamental mechanisms underpinning the role of manganese for the peritectic phase transition. The literature describes several approaches that investigate the behaviour of peritectic multi-component alloys, but all of these involve strong interdependencies between alloying elements, and thus do not explain the effect of individual alloy components. The aim of this thesis was to gain further insight on the specific influence of manganese on the δ‑ferrite to γ‑austenite phase transformation. This was achieved using a combination of high-temperature laser-scanning confocal-microscopy (HTLSCM) and dipping experiments. A series of experiments on alloys containing 0 to 6 wt. % manganese were performed utilizing both experimental techniques. Although the HTLSCM experiments did not show a particular effect of manganese on the “massive transformation”, the previous research findings that the primary solidified δ-ferrite and the associated undercooling determine the “massive transformation”, could be supported. Both HTLSCM and dipping results confirmed that the position relative to the peritectic point is of great importance for the solidification behaviour of peritectic steels. However, the dipping results for steels containing more than 1 wt. % manganese deviate from this statement and indicate other influencing factors for higher alloyed steels.