Abstract: The precipitates in 20Cr11MoVNbNB steel of quenched and tempered at 700℃, and subsequently aged at 55o~650℃ for 5000h were studied by the means of electrolytic extraction, x-ray diffraction, election microscope etc. It is established that M28C6 and MC are mainly precipitates in 20Cr11MoVNbNB Steel. The coarsening kinetics of M22C6 and MC have same cubic law controlled by block diffusion, and regardless of their original precipitating positions. The coarsening rate of M23C6 is faster than that of MC, and the coarsening rates of the two carbides are controlled by slow diffusion alloy element atoms which constitute the phases.

Key words: 沉淀, 合金钢, 时效