CONCLUSION
The ThermoCalc software package, using the thermodynamic databases of TCFE7 was employed to study the precipitation of nitrides and carbonitrides in common microalloyed line pipe steels.
- Higher concentration of titanium increases the precipitation temperatures of titanium nitrides by approximately 70K, suggesting larger titanium nitrides.
- The niobium concentration up to 0.12 wt% in a Ti and Nb microalloyed steel shows no influence on the precipitation temperature of nitrides, whereas the formation temperature of niobium carbides is increased substantially up to 0.03 wt% Nb. The nitride precipitates contain a high concentration of titanium while carbides mostly formed of niobium.
- Titanium concentration increases the precipitation temperatures of titanium nitrides in a Ti and Nb microalloyed steel. However, the precipitation temperatures of both nitrides and carbides increase significantly with Nb concentration.
The results are in good agreement with experimental data in the literature, highlighting the suitability of primary calculation approach to the design of new alloys and heat treatment processes of microalloyed steels.