Approximately 30% of hot-work tool steels are used as tools for die casting of light metal alloys. Due to the rapidly advancing development, the casting parts and thus the tools become larger. This results in problems with the heat treatment. Because of the large background temperature, the high cooling rates requested for a purely martensitic structure can not been reached and bainite occurs. The aim of this work is to determine the influence of alloying elements Mo, Mn, Cr, Ni, Si, V, and C on the bainite transformation. Laser alloying was used to vary the elements individually and produce dilatometer samples. From the dilatometer data various CCT charts were created. For the comparison of the CCT charts microstructure investigations were necessary. From the light optical microscope investigations former austenite grain sizes were determined, because they have a great influence on the transformation behaviour. Other influencing factors are carbides which handicap the growth of the grains but also deprive the alloying elements from the matrix. For their detection SEM investigations were carried out. With EDX analysis the exact composition of the matrix has been determined. Appending all these investigations, the influence of individual elements on the bainite transformation could be determined.