High Temperature Oxidation and Its Effects on Microstructural Changes of Hot-Rolled Low Carbon Non-oriented Electrical Steels During Air Annealing Article uri icon

abstract

  • This paper reports the influence of temperature on external oxidation and its effect on microstructural changes of hot-rolled non-oriented electrical steels during air-annealing treatments. Annealing during 150 min at temperatures above 700 °C, promotes the formation of two oxide layers: an inner iron–silicon–aluminum oxide and an outer three-layered wüstite–magnetite–hematite oxide. Thickness and oxide characteristics depend on temperature and influence other microstructural changes. Significant decarburization occurs at 800 and 850 °C when thin and cracked oxide structures are formed. At higher temperatures, decarburization becomes slower due to the increase of oxide thickness and a transition from cracked to crack-free structures, until at 950 and 1,050 °C, decarburization is practically inhibited. Absence of decarburization is confirmed by the increment of carbides volume fraction resulting from γ-Fe → α-Fe %2b Fe3C phase transformation. Finally, slow decarburization leads to normal grain growth, while intense decarburization favors abnormal growth with significant reduction in the amount of secondary particles. © 2015, Springer Science%2bBusiness Media New York.

publication date

  • 2015-01-01