Figure 5 shows the phase diagram of the High-Nb steel as a function of carbon concentration, demonstrating that titanium nitride precipitates in steels with carbon concentrations <0.06 wt% form at temperatures ~50K higher than the steels with higher carbon concentrations. Whereas niobium carbonitride precipitates, form at much lower temperatures in low carbon steels. It suggests that titanium nitride precipitates in low carbon steels are expected to be larger in size than in alloys with higher concentrations of carbon (above 0.06 wt%). Steel 4 in Table 3 contains 0.05 wt% C and therefore it is anticipated to include larger TiN precipitates than the other alloys. The formation temperature of Nb carbonitrides is increased considerably to ~1400K by carbon concentration up to 0.02 wt% and then gradually increased to ~1520K at 0.1 wt% carbon. The niobium carbonitride precipitates contain higher ratios of carbon to nitrogen and also contain a small amount of titanium. The elemental fractions change by temperature and carbon concentration.