Effect of Nb Solute and NbC Precipitates on Dynamic or Static Recrystallization in Nb Steels

摘要

Nb is often considered to be a powerful alloying element for controlling the recrystallization process in microalloyed high strength steels.However,Nb can be presented either as solute in solution,where it is thought to exhibit a strong solute drag effect,or as NbC precipitates,which are thought to be effective at pinning grain boundaries.Therefore,it is very important to quantitatively measure Nb in solution or in NbC precipitates.A quantitative analysis method of Nb in solution and in precipitates was proposed.The test procedure involved chemical dissolution,filtration and inductively coupled plasma atomic emission spectroscopic(ICP-AES) analysis.The amount of Nb in solution in Nb-microallyed steels under different treatment conditions was evaluated.The results show that the niobium and carbon contents in steels have a great effect on niobium dissolution kinetics.The solute Nb is more effective to retard dynamic recrystallization,while the NbC precipitates are more effective to inhibit static recrystallization.The results may help to comprehend effect of Nb in steels,and provide some guides in the design of new high strength Nb-bearing steels.