Effect of Solutes on Recrystallization and transformation of Austenite in IF Steels

摘要

With the absence of the precipitation of carbides or carbo-nitrides, the processing behavior of austenite in IF steels is determined in large part by the solutes. The solutes are found to influence the behavior of austenite in the following manner: 1) The recrystallization of austenite is retarded by all the solutes examined, including titanium and carbon. 2) All the solutes increased the flow stress of austenite at the lower finishing temperatures. At temperatures above 1050℃ the flow stress was only increased by sulfur and phosphorus. 3) An increase in quenched ferrite hardness is associated with the solute additions, with the largest effect being in the case of the B steel, where non-polygonal ferrite is easily formed. This increase in hardness is associated with the higher dislocation density of non-polygonal ferrite. The observed behavior of the specially designed steels is consistent with the suggestion that B, C, Mo, Nb, P, and S are all effective grain boundary segregants. A study of the relative effect of these solutes on the rate of austenite grain growth would help confirm this suggestion. Finally, Cahn's model of solute drag needs to be modified if it is to account for the retardation of the recrystallization of austenite by B, C, P, and S.