Relevant experimental phase equilibria were used with the THERMOCALC program to refine thermodynamic parameters for low-temperature region, in the steels with composition 0.4 to 2.5 wt.% Cr, 0 to 1 wt.% Mo, and 0 to 0.5 wt.% V. The refined parameters were used to calculate phase relationships, which were then compared with experimental results. Results of experiments indicate that M7C3 replaces M23C6 carbides in the temperature region betweeen 773 and 873 K. Similar behavior was also found for molybdenum-rich phases M6C and M2C. Some modifications of existing thermodynamic parameters in the low temperature region were necessary.