Knowledge of the TTT (Time-Temperature-Transformation) or CCT (Continuous- Cooling-Transformation) diagrams of steels is an important factor in the thermo-mechanical processing of steels. Much experimental work has been undertaken to determine such diagrams. Significant works have been written which can calculate TTT and CCT diagrams for steels. The aim of the present work is to show the developed model that can provide accurate enough TTT and CCT diagrams for steel 42 CrMo4 (where the austenitisation temperature was 1050°C). The calculated results are compared by the experimental results. The developed TTT phase transformation diagrams based on FEM-based phase elements and the star-like cooling simulation make it possible to create virtual CCT diagram data.