Papers by Keyword: Cold Charging

Abstract: The aim of this work is to investigate the dissolution behavior of Nb in hot charging hot rolling configurations. To do so, an indirect experimental procedure is used to quantify the amount of Nb present in solution before rolling. The method is based on the effect of dissolved Nb on static recrystallization kinetics due to its solute drag effect. After different thermal cycles, simulating cold and hot charging conditions, double hit torsion tests have been performed with a 0.23%C steel microalloyed with 0.03% Nb. By means of these tests, the static softening behavior has been determined. Comparison of the recrystallization times allows indirect evaluation of the amount of Nb in solid solution after each treatment. The results have been correlated with the precipitation state of the samples.

Abstract: Comparison of grain growth of fine-grained and coarse-grained austenite in a Nb-V-Ti microalloyed steel during reheating or equalization at the same temperature was investigated using cold-charging and hot-charging specimens respectively in this study. The results show that the different grain growth behavior appears in fine-grained and coarse-grained austenite. The uniform grain growth and lower growth rate at reheating temperature studied was found in fine-grained austenite, while partial grain growth and higher growth rate was present in coarse-grained austenite. During reheating or equalization, the slow growth rate in fine-grained austenite may be contributed to stronger pinning force of fine precipitates while higher grain growth rate in coarse-grained austenite were believed to the result of lager size difference among part of grains. Grain coarsening occurs in fine-grained austenite as result of precipitate unpinning at extending holding time, but coarse-grained austenite remained wide size distribution at the same condition and this should not be considered as grain coarsening. coarse-grained austenite remained wide size distribution at the