The diploma thesis includes determining the optimal temperature for the heat treatment of the PROTAC 500M steel. The emphasis was on the influence of heat treatment on mechanical properties as well as on the appropriate combination of these. The problems discussed include mainly the measurements of hardness.
The temperature of the phase transformations Ac1 and Ac3 was determined by means of the quench type and dilatometry, and calculated using known empirical equations.
In order to determine the optimal interval of the quenching temperatures, the steel samples were emitted from different temperatures above the point Ac3 in water. We low temperature tempered the tempered steel immediately after hardening. Tempered samples have a martensitic microstructure. In the martensitic basis, small carbides are present. Areas represent self-tempering martensit. With the rising tempering temperature, carbide excretion increases.
The results of the metallographic analysis and mechanical tests show that the hardening of 850°C and tempering at 200°C achieved the most appropriate combination of mechanical properties.