The secondary phase particles in Ti-V-Nb microalloyed linepipe steel were investigated using carbon extraction-replica technique.The results show there are a large number of fine dispersed particles in the steel.The larger particles like square contain higher Ti and lower Nb.The smaller particles of irregular shape contain lower Ti and higher Nb. The particles of more than 20nm size contain lower V. The electron diffraction analysis shows the particles have face-centered cubic structure. The dispersed particles retard the growth of austenite grains markedly.The austenite grains in the steel heated at below 1 150 ℃ grow at very low speed.The austenite grains in the steel heated at above 1 150 ℃ grow markedly.
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