The paper is focused on analysing the pearlitic steel phase transformations and their influence on the mechanical properties. The intention is to perform a detailed analysis of the heat treatment process using the exact heating temperature and chemical composition to achieve the optimal mechanical properties of the tool. The key area is monitoring and regulating the heat treatment. This technology is constantly undergoing an optimisation process and is an effort to introduce new trends in monitoring phase transformations and processes. The use of non-destructive methods is an adequate tool. The principle is to determine the exact structural phase at a given moment, which can be very difficult when a complex shaped part is heat treated. Which precludes the use of some other methods of phase transformation analysis. Specifically, the determination of the exact moment of finish of the austenitisation process is eminent. The monitoring of these processes will be ensured by both a non-contact pyrometer and also by the AE method with an adequate sensor and waveguide. The resulting structural phases formed after the heat treatment will be evaluated by electron microscopy, followed by the analysis of the mechanical properties of selected steels.