Austenite formation during intercritical annealing in C-Mn cold-rolled dual phase steel
来源期刊：中南大学学报(英文版)2015年第4期
论文作者：LI Sheng-ci KANG Yong-lin ZHU Guo-ming KUANG Shuang
文章页码：1203 - 1211
Key words：dual phase steel; confocal laser scanning microscope; dilatometry; austenitizing; in situ observation
Abstract: Two different kinds of experimental techniques were used to in-situ study the austenite formation during intercritical annealing in C-Mn dual phase steel. The microstructure evolution was observed by confocal laser scanning microscope, and the austenite isothermal and non-isothermal transformation kinetics were studied by dilatometry. The results indicate that banded structure is produced for the reason of composition segregation and the competition between recrystallization and phase transformation. Austenite prefers to nucleate not only at ferrite/ferrite grain boundaries, but also inside the grains of ferrite. Furthermore, the austenitizing process is accomplished mainly via migration of the existing austenite/ferrite interface rather than nucleation of new grains. The incubation process can be divided into two stages which are controlled by carbon and manganese diffusion, respectively. During the incubation process, the nucleation rate of austenite decreases, and austenite growth changes from two-dimensional to one-dimensional. The partitioning coefficient, defined as the ratio of manganese content in the austenite to that in the adjacent ferrite, increases with increasing soaking time.
LI Sheng-ci(李声慈)1, KANG Yong-lin(康永林)1, ZHU Guo-ming(朱国明)1, KUANG Shuang(邝霜)2
(1. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. Technical Research Institute, Shougang Co., Ltd., Beijing100043, China)
Abstract:Two different kinds of experimental techniques were used to in-situ study the austenite formation during intercritical annealing in C-Mn dual phase steel. The microstructure evolution was observed by confocal laser scanning microscope, and the austenite isothermal and non-isothermal transformation kinetics were studied by dilatometry. The results indicate that banded structure is produced for the reason of composition segregation and the competition between recrystallization and phase transformation. Austenite prefers to nucleate not only at ferrite/ferrite grain boundaries, but also inside the grains of ferrite. Furthermore, the austenitizing process is accomplished mainly via migration of the existing austenite/ferrite interface rather than nucleation of new grains. The incubation process can be divided into two stages which are controlled by carbon and manganese diffusion, respectively. During the incubation process, the nucleation rate of austenite decreases, and austenite growth changes from two-dimensional to one-dimensional. The partitioning coefficient, defined as the ratio of manganese content in the austenite to that in the adjacent ferrite, increases with increasing soaking time.
Key words:dual phase steel; confocal laser scanning microscope; dilatometry; austenitizing; in situ observation
