Thermal stability and phase transformation of the hot-rolled TRIP steels exposed to coiling temperatures of 350 to 500 C

Abstract

The retained austenite in hot rolled TRIP steels can decompose into other phases during the coiling process and cooling process, which can produce serious inhomogeneity of the TRIP sheet steels. In order to evaluate the decomposition behavior of retained austenite, the simulation of hot rolling and coiling processes and in-situ heating observations have been made for the hot-rolled C-Mn-Si TRIP steels. It was found that retained austenite decomposes into various phases depending on coiling temperatures ranging from 350 to 500degreesC, such as carbide-free bainitic ferrite, ferrite associated with cementite and pearlite. The step by step sequences of the decomposition behavior are discussed in terms of the carbon concentration variation and the thermal stability of retained austenite depending on coiling temperatures and holding times.