Abstract: By using carbon extraction replica technology, the response of particle in Ti-Nb-V microalloyed X-60 Steel to Weld Thermal Cycle is investigated. Experiment results and analysis show that the particles in the steel change from irregular shape to cubicle one after thermal cycle. t8/5 has a great effect on the chemical composition, mean size and number per unit area of the particles after weld thermal cycle. When t8/5 change from 10s to 45s, all particles remain rich in Ti, the mean size increases and the number per unit area decreases, indicating that no re-precipitation occurs. When t8/5 changes from 45s to 120s, particles rich in Nb + V appear, the mean size decreases and the number per unit area increases, indicating that re-precipitation occurs in case of large t8/5.

Key words: Coarsening, Dissolution, Re-precipitation, Second phase particle, Weld thermal cycle