Prediction of Decarburized Ferrite Depth of Hypoeutectoid Steel with Simultaneous Oxidation

The objective of this paper is to describe a method of calculating the decarburized ferrite depth and scale thickness during heating and cooling for hypoeutectoid steel in ambient atmosphere. The decarburization behavior in hypoeutectoid steel is divided into three regions. In temperature region above A3 ferrite is not formed during decarburization from austenite with a carbon concentration C = 0.0 wt%. In temperature region below A3 (C = 0.0 wt.%) and above A3 (C = C0) the decarburized ferrite forms from austenite during decarburization, but its carbon concentration ranges from 0.0 to the nominal carbon concentration C0. Finally, in the temperature region below A3 (C = C0) austenite transforms to ferrite + austenite or ferrite + cementite and the decarburized ferrite forms from ferrite + austenite or ferrite + cementite by surface decarburization with the appropriate equilibrium concentration. Separate decarburization models were developed for the three temperature regions due to the difference in decarburization behavior. The proposed model also handles simultaneous oxidation. The quantitative information obtained on the oxidation and decarburization characteristics is in good agreement with the experiments.