Precipitation behavior of composite precipitates in Nb-Ti micro-alloy EH36 offshore steel
Based on the principal component regression analysis of the factors affecting the yield strength of EH36 offshore steel,combined with the solid solution precipitation calculation of composite precipitation phase and the classical precipitation kinetics theory,the main factors affecting the yield strength of EH36 offshore steel and the precipitation behavior of composite precipitation phase in γwere systematically studied,and the influence of austenite deformation and energy storage during rolling on the precipitation kinetics of composite precipitation phase was discussed.The results show that the main factors affecting the yield strength of EH36 offshore steel are Ti,Nb and N.MN and M(C,N)began to precipitate at 1728.5 K and 1430.0 K,respectively,and were mainly(Ti,Nb)N and(Nb,Ti)C.In the austenite phase region,the maximum precipitation amounts of MN and M(C,N)are 0.016 5％and 0.027 7％respectively,and the maximum precipitation volume fractions are 0.000 228％and 0.000 389％respectively.The fastest precipitation temperatures for grain boundary nucleation are 1580.3 K and 1228.3 K respectively.With the increase of deformation energy storage,the relative nuc-leation rate of MN and M(C,N)increases,the incubation period of precipitation is obviously shortened and the precipitation strengthening effect is enhanced.
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