ON THE SWERVING OF STRENGTH CURVE FOR STEEL 20Cr11MoVNbNB

Study was made on the swerving of the curves of strength and hardness vs L-M parameterP=T(20+lgt)for steel 20Crl 1MoVNbNB aged at 550.600 and 650℃ for 0—5000 h,Tbeing aging temperature in K and taging time in h.The swerving seems to be due to:(1)thecoarsening of the mean size of principal precipitate M_(23)C_6,(2)the precipitation of Lavesphase MoFe_2;(3)the decrease of Mo content in matrix and(4)the recovery andrecrystallization of the matrix phase.