The Effect of Heating Rate on the Microstructure of a Soft-Annealed Medium Carbon Steel, Steel Research International, 2017, Vol. 87 No. 9999, pp. 1-9 (1700158)
Spyros Papaefthymiou, Constantinos Goulas, Felipe Manuel Castro Cerda, Nico Geerlofs, and Roumen Petrov
Abstract
A comparative study on the microstructural changes after conventional (20oC/s) and
ultrafast (300oC/s) heating is performed on a medium carbon steel in the soft annealed
condition. Continuous-heating dilatometry experiments are carried out. The phase
transformations and the volume phase fraction of austenite are determined among other
microstructural changes. The microstructure is first observed using Optical Microscopy
(OM), further characterized by Scanning (SEM), and detailed analyzed by Transmission
Electron Microscopy (TEM). The effect of heating rate on the kinetics of cementite
dissolution and austenite formation is rationalized. The experimental results are compared
with Dictra calculations, and the possible effects on the kinetics of diffusion-controlled
austenite formation are rationalized as well. Metallographic observations indirectly suggest
the enhanced nucleation of austenite above Am.