It was proved that the volume fraction of retained austenite (RA) in the quenched samples of the 0.80%C, 1.80%Cr, 0.23%Mo, 0.17%V steel on the working rolls of cold sheet rolling mills depends on their sizes. During tempering of this steel at 160°C the RA is stabilized so strongly that it is transformed neither by means of stresses nor strains. It was computed that in this steel, every 1% by volume of RA increases its fracture toughness (Klc) by about 5%. Under conditions of dynamic loading the power of effect of RA is increased to about 7%.