IN SITU OBSERVATION OF INTRAGRANULAR ACICULAR FERRITE NUCLEATED ON COMPLEX TITANIUM–CONTAINING INCLUSIONS IN TITANIUM DEOXIDIZED STEEL
HU Zhiyong 1, YANG Chengwei 2, JIANG Min 1, YANG Guangwei1, WANG Wanjun 1,WANG Xinhua 1
1.School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083
2. Wuhan Iron and Steel (Group) Corp, Wuhan 430080
Cite this article:
HU Zhiyong YANG Chengwei JIANG Min YANG Guangwei WANG Wanjun WANG Xinhua . IN SITU OBSERVATION OF INTRAGRANULAR ACICULAR FERRITE NUCLEATED ON COMPLEX TITANIUM–CONTAINING INCLUSIONS IN TITANIUM DEOXIDIZED STEEL. Acta Metall Sin, 2011, 47(8): 971-977.
Abstract The nucleation of intragranular acicular ferrite (IAF) on complex titanium–containing inclusions for titanium deoxidized steel was observed dynamically by confocal scanning laser microscope (CSLM), and the effects of average austenite grain size and cooling rate on the nucleation of IAF was systematically investigated by using OM, FE–SEM and EDS. Furthermore, the mechanism of IAF nucleation on the complex titanium–containing inclusions was studied by using EPMA in detail. The results show that the starting formation temperature of IAF firstly increases with increasing austenite grain size, then decreases. With the increase of cooling rate, the volume fraction of IAF increases obviously due to the increase of the starting formation temperature. Mn–deplete zone (MDZ) is considered to be a dominant driving force for the nucleation of IAF. In addition, it is found that the range of starting formation temperature of IAF is 550—633 ℃ with austenite grain size in the range of 132—255 μm. Volume fraction of IAF obtained at room temperature is up to 90% with austenite grain size of 176 μm and a cooling rate of 5 ℃/s in this experiment condition.