The effect of titanium on the hardening behaviour of medium carbon steel alloyed with chromium and molybdenum has been studied. It has been shown that the superhardening could be produced without superheating. The optimum titanium content for superhardening is between 0.03-0.05 wt%, and above this optimum level the hardening decreases with increasing titanium content. By dilatometry, it is shown that the optimum titanium content results in large hardness increases due to a strong retardation of the ferrite/pearlite and bainite transformations, this being particularly noticeable for the bainite transformation. However the superhardening behaviour weakens as the melting temperature is increased from 1550 to 1650 degrees C, and the superhardening effect completely disappears after a spheroidization annealing treatment.